천문학회보 (The Bulletin of The Korean Astronomical Society) (The Bulletin of The Korean Astronomical Society)
한국천문학회 (The Korean Astronomical Society)
- 반년간
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- 1226-2692(pISSN)
과학기술표준분류
- 지구과학(지구/대기/해양/천문) > 천문학
제45권1호
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I review the status of the concordance (standard) LCDM model of cosmology in light of current observations discussing about the apparent tensions in estimation of the key cosmological parameters. I will also briefly discuss the future of the field at the era of the next generation of the astronomical/cosmological surveys.
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1980년 3월 국립천문대에 들어와 14m 전파망원경 건설사업 준비 단계부터 시작한 전파천문연구는 이제 40년이 되었다. 1985년 일본 동경대에서 일본국립천문대 노베야마 45m 전파망원경을 사용하여 학위를 마친 후 귀국하여 한국천문연구원 대덕 14m 전파망원경의 설치 운영과 이를 활용한 관측연구 및 한국우주전파관측망의 추진, 건설과 그 관측연구에 이르기까지 그 간의 전파천문연구에 대해서 발표하고자 한다.
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Cosmology is a study to understand the origin, fundamental property, and evolution of the universe. Nowadays, many observational data of galaxies have become available, and one needs large-volume numerical simulations with good quality of the spatial distribution for a fair comparison with observation data. On the other hand, since galaxies' evolution is affected by both gravitational and baryonic effects, it is nontrivial to populate galaxies only by N-body simulations. However, full hydrodynamic simulations with large volume are computationally costly. Therefore, alternative galaxy assignment methods to N-body simulations are necessary for successful cosmological studies. In this talk, I would like to introduce the MBP-galaxy abundance matching. This novel galaxy assignment method agrees with the spatial distribution of observed galaxies between 0.1Mpc ~ 100Mpc scales. I also would like to introduce mock galaxy catalogs of the Horizon Run 4 and Multiverse simulations, large-volume cosmological N-body simulations done by the Korean community. Finally, I would like to introduce some recent works with those mock galaxies used to understand our universe better.
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Structure in the universe forms hierarchically with the small scales forming first and merging into larger scales. Galaxy clusters are at the pinnacle of the formation process. Peering far into the universe, we can observe galaxy clusters early in their evolution. SpARCSJ1049+56 is a galaxy cluster located at a redshift of 1.71. It has been shown to be rich in cluster galaxies, to have intense star formation, and to have a significant amount of molecular gas. Through careful control of systematics, we detected the weak-lensing signal from this distant galaxy cluster. I will present our HST infrared weak-lensing detection of the cluster with a focus on the method. Our lensing analysis found that the cluster is massive and is rare in a LambdaCDM universe. I will also present the Chandra X-ray discovery of cold gas coincident with the intense star formation and discuss the implications of the detection.
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We present an improved weak-lensing (WL) study of the high-z (z=0.87) merging galaxy cluster ACT-CL J0102-4915 ("El Gordo"), the most massive system known to date at z > 0.6. El Gordo has been known to be an exceptionally massive and rare cluster for its redshift in the current ΛCDM cosmology. Previous multi-wavelength studies have also found that the cluster might be undergoing a merging event showing two distinctive mass clumps and radio relics. The previous WL study revealed a clear bimodal mass structure and found that the entire system is indeed massive (M200a = (3.13 ± 0.56) × 1015 Msun). This mass estimate, however, was obtained by extrapolation because the previous HST observation did not extend out to the virial radius of the cluster. In this work, we determine a more accurate mass estimate of the cluster using WL analysis utilizing a new set of WFC3/IR and wide-field ACS observations. While confirming the previous bimodal mass structure, we find that the new data yield a ~20% lower mass for the entire system (M200a = (2.37 ± 0.28) × 1015 Msun). We also discuss the rarity of the cluster in the ΛCDM paradigm and suggest an updated merging scenario based on our new measurement.
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Kim, HyeongHan;Jee, M. James;Rudnick, Lawrence;Parkinson, David;Finner, Kyle;Yoon, Mijin;Lee, Wonki;Brunetti, Giangranco;Bruggen, Marcus;Collier, Jordan D.;Hopkins, Andrew M.;Michalowski, Michal J.;Norris, Ray P.;Riseley, Chris 30.1
The ASKAP-EMU survey is a deep wide-field radio continuum survey designed to cover the entire southern sky and a significant fraction of the northern sky up to +30°. Here, we report a discovery of a radio relic in the merging cluster SPT-CL J2023-5535 at z=0.23 from the ASKAP-EMU pilot 300 square degree survey (800-1088 MHz). The deep high-resolution data reveal a ~2 Mpc-scale radio halo elongated in the east-west direction, coincident with the intracluster gas. The radio relic is located at the western edge of this radio halo stretched ~0.5 Mpc in the north-south orientation. The integrated spectral index of the radio relic within the narrow bandwidth is α1088MHz800MHz = -0.76 ± 0.06. Our weak-lensing analysis shows that the system is massive (M200 = 1.04 ± 0.36 × 1015M⊙) and composed of at least three subclusters. We suggest a scenario, wherein the radio features arise from the collision between the eastern and middle subclusters. Furthermore, the direct link between the local AGN and the relic along with the discontinuities in X-ray observation hint us that we are looking at the site of re-acceleration. -
We present the properties of circumnuclear gas associated with the AGN located in the center of Abell 1644-South. A1644-S is the main cluster in a merging system, which is also known for gas sloshing in its core as seen in X-ray. The X-ray emission of A1644-S shows a rapidly declining profile, indicating the presence of cooling gas flow. This flow of cool gas may fuel the supermassive black hole embedded in the brightest cluster galaxy, leading to the activation of the central AGN. Indeed, we find a parsec-scale bipolar jet feature in the center of A1644-S in our recent KaVA observation, which implies that its central AGN is likely to have been (re)powered quite recently. In order to verify the hypothesis that cooling gas flow in the cluster core can (re)activate the central AGN, we probe the cold gas properties of the central 1 kpc region of A1644-S using the archival VLA and ALMA data. Based on the spatially resolved morphology and kinematics of HI and CO gas, we challenge to identify inflow/outflow gas streams and clumps. We study the role of circumnuclear cool gas in fueling the centrally located cluster AGN in the cool-core environment. We also discuss how the feedback due to the (re)powered AGN affects the surrounding medium.
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A merger or interaction between galaxy clusters is one of the most violent events in the universe. Thus, an interacting cluster is an optimum laboratory to understand how galaxy properties are influenced by a drastic change of the large-scale environment. Here, we present the observational evidence that bars in disk galaxies can form by cluster-cluster interaction and the bar formation is associated with star-formation enhancement. We investigated 105 galaxy clusters at 0.015Kim, Seonwoo;Contini, Emanuele;Choi, Hoseung;Han, San;Lee, Jaehyun;Oh, Sree;Kang, Xi;Yi, Sukyoung K. 31.2
Mass segregation, a tendency of more massive galaxies being distributed closer to the cluster center, is naturally expected from dynamical friction, but its presence is still controversial. Using deep optical observations of 14 Abell clusters (KYDISC) and a set of hydrodynamic simulations (YZiCS), we find in some cases a hint of mass segregation inside the virial radius. Segregation is visible more clearly when the massive galaxy fraction is used instead of mean stellar mass. The trend is more significant in the simulations than in the observations. To find out the mechanisms working on mass segregation, we look into the evolution of individual clusters simulated. We find that the degree of mass segregation is different for different clusters: the trend is visible only for low-mass clusters. We compare the masses of galaxies and their dark haloes at the time of infall and at the present epoch to quantify the amount of tidal stripping. We then conclude that satellites that get accreted at earlier epochs, or galaxies in more massive clusters go through more tidal stripping. These effects in combination result in a correlation between the host halo mass and the degree of stellar mass segregation. This is a work submitted to The Astrophysical Journal (under review).The surface brightness fluctuation (SBF) is one of the most crucial distance indicators for unresolved stellar systems at large distances. Here, we present an evolutionary population synthesis model of the surface brightness fluctuation (SBF) for normal and He-enriched simple stellar populations (SSPs). Our SBF model for the normal-He population agrees well with other existing models, but the He-rich populations bring about a substantial change in the SBF of SSPs. Our normal-He SBF model well reproduces the observed SBFs of the Milky Way globular clusters, but the SBFs of early-type galaxies in the Virgo Cluster are placed between the normal-He and He-rich SBF models. We show that the SBF-based distance estimation would be affected by up to a 10-20% level in I- and near-IR bands at given colors. Finally, we propose that when combined with independent metallicity and age indicators such as Mg2 and H, the UV and optical SBFs can readily detect underlying He-rich populations in unresolved stellar systems. Given the degree of the SBF variation resulting from the population difference, we suggest that the distance measurement before the proper in-depth analysis of stellar populations should be done with great caution.An independent determination of H0 is crucial given the growing tension of the Hubble constant (H0). In this work, we present a new determination of H0 using velocities and Tip of the Red Giant Branch (TRGB) distances to 33 galaxies in front of the Virgo Cluster. We model the infall pattern of the local Hubble flow modified by the Virgo mass, as a function of the H0, the radius of the zero-velocity surface R0, and the intrinsic velocity scatter. Fitting velocities and TRGB distances of 33 galaxies to the model, we obtain H0 = 65.6 +/- 3.4 (stat) +/- 1.0 (sys) km/s/Mpc and R0 = 6.96 +/- 0.35 Mpc. Our local H0 is consistent with the global H0 determined from cosmic microwave background radiation, showing no tension.Massive Compact Elliptical Galaxies (MCEGs) found in the local universe are as massive as normal galaxies but extremely compact (M∗ > 1011 Msun, Reff < 1.5 kpc). They are considered to be the relics of red nugget galaxies found at high redshift. They are not likely to have undergone many mergers, keeping their original mass and size. Moreover, it is expected that they host a dominant population of red (metal-rich) globular clusters rather than blue (metal-poor) ones. Indeed, Beasley et al. (2018) found that the color distribution of the cluster system of NGC 1277 is unimodal, showing only a red population. However, NGC 1277 is the only case whose cluster system was studied among MCEGs. In this study, we investigate globular cluster systems of 14 nearby MCEGs with a homogeneous data set of HST/WFC3 F814W/F160W archive images. We detect tens to hundreds of globular clusters in each galaxy and examine their color distributions. Surprisingly, the fractions of red globular clusters are similar to those of normal galaxies, and are much lower than that of NGC 1277. We additionally obtain Gemini/GMOS-N g'r'i' images of PGC 70520, one of the 14 nearby MCEGs, to detect more globular clusters from deeper and wider images. We will discuss the results from the Gemini data combined with the results from the HST data in relation with the formation of MCEGs.Jellyfish galaxies show spectacular features such as star-forming knots and tails due to strong ram-pressure stripping in galaxy clusters. Thus, jellyfish galaxies are very useful targets to investigate the effects of ram-pressure stripping on the star formation activity in galaxies. Integral field spectroscopy (IFS) studies are the best way to study star formation in jellyfish galaxies, but they have been limited to those in low-mass galaxy clusters until now. In this study, we present a Gemini GMOS/IFU study of three jellyfish galaxies in very massive clusters (M_200 > 10^15 Mo). The host clusters (Abell 2744, MACSJ0916.1-0023, and MACSJ1752.0+4440) are X-ray luminous and dynamically unstable, suggesting that ram-pressure stripping in these clusters is much stronger than in low-mass clusters. We present preliminary results of star formation rates, kinematics, dynamical states, and ionization mechanisms of our sample galaxies and discuss how ram-pressure stripping relates with the star formation activity of jellyfish galaxies in massive clusters.Ram pressure stripping (RPS) which is known to be one of the key effects that can remove the interstellar gas in the dense environment, can be described as a simple momentum transfer relation (Gunn & Gott 1972). However, it has been suggested that the actual gas stripping process is likely more complicated than Gunn & Gott's prescription due to the complexity of gas physics such as compression, cooling and heating. By comparing the gas truncation radius predicted by theory with the stripping radius measured from the HI observation of Virgo cluster galaxies, we attempt to verify how well the RPS process can be understood by momentum transfer alone. Among the sample of galaxies undergoing active RPS, we generally find a good agreement between what is predicted and what is observed within the measurement uncertainties. However, those galaxies with the signs of other environmental effects than RPS such as tidal interaction, and/or the ones likely at relatively early or later stages of RPS show some offsets between the theory and the observation. These results imply that Gunn & Gott's formula works reasonably well in a broad sense when the RPS is a dominant process and the surrounding environment at the current location of the sample can be well defined. Otherwise, the impact of the second mechanism, as well as the (current and past) environment of the sample, should be more carefully reviewed to assess the impact of RPS on galaxy evolution.Our HI monster sample is a set of local HI-rich galaxies identified by the ALFALFA survey (Arecibo Legacy Fast Survey ALFA) at z<0.08. Intriguingly, they are also found with a relatively large molecular gas reservoir compared to the galaxies with similar stellar mass and color, yet their star formation rate is quite comparable to normal spirals. This makes our HI monsters good candidates of galaxies in the process of gas accretion which may lead to the stellar mass growth. One feasible explanation for their relatively low star formation activity for a given high cool gas fraction is the gas in monsters being too turbulent to form stars as normal spirals. In order to verify this hypothesis, we probe the molecular gas kinematics of 10 HI monsters which we observed using the Atacama Large Millimeter/sub-millimeter Array (ALMA). We utilize the tilted ring model to investigate what fraction of the molecular gas in the sample is regularly and smoothly rotating. In addition, we model the molecular gas disk using the GALMOD package of the Groningen Image Processing System (GIPSY) and compare with the observations to identify the gas which is offset from the 'co-planar differential rotation'. Based on the results, we discuss the possibility of gas accretion in the sample, and the potential origin of non-regularly rotating gas and the inefficient star formation.The Milky Way (MW) and other systems including M31 and Cen A have flattened structures of their satellites (Disk of Satellites, DoS). Such structures are rare in simulations under the ΛCDM paradigm. DoS is known to depend mainly on 1) the alignment of satellite orbits and 2) the degree of central concentration of satellites. In this work, we examine quantitatively how these two parameters affect the flatness of a system. We find that the MW-like DoS is rare in IllustrisTNG100 simulation because its two parameters are out of the 1-s range and furthermore the MW has a structure more flattened than the other systems having similar parameters. Besides, we propose a new criterion for the MW-like systems superseding the conventional ones such as major-minor axis ratio of the MW's DoS with a value of 0.183. Each satellite system has a specific orbital combination and thus has a particular distribution of its parameters (and thus flatness). The median of the distribution is set as the representative value of each system. And the representative value of the MW can be used as a new criterion for classifying the MW-like DoS. We reconstruct the orbital combination of the observed MW satellites using GAIA DR2 data and find the systems in the simulation that have representative values similar to the new criterion from the reconstructed MW system. This allows us a new interpretation on the rarity of MW-like DoS in cosmological simulations.Shin, Eun-jin;Jung, Minyong;Kwon, Goojin;Kim, Ji-hoon;Lee, Joohyun;Jo, Yongseok;Oh, Boon Kiat 34.1
The recent discovery of diffuse dwarf galaxies that are deficient in dark matter appears to challenge the current paradigm of structure formation in our Universe. We describe the numerical experiments to determine if the so-called dark matter deficient galaxies (DMDGs) could be produced when two gas-rich, dwarf-sized galaxies collide with a high relative velocity of ~ 300km/s. Using idealized high-resolution simulations with both mesh-based and particle-based gravito-hydrodynamics codes, we find that DMDGs can form as high-velocity galaxy collisions separate dark matter from the warm disk gas which subsequently is compressed by shock and tidal interaction to form stars. Then using a large simulated universe ILLUSTRISTNG, we discover a number of high-velocity galaxy collision events in which DMDGs are expected to form. However, we did not find evidence that these types of collisions actually produced DMDGs in the ILLUSTRISTNG100-1 run. We argue that the resolution of the numerical experiment is critical to realize the "collision-induced" DMDG formation scenario. Our results demonstrate one of many routes in which galaxies could form with unconventional dark matter fractions.Reverberation mapping is one of the best ways to investigate the physical mechanism of broad-line regions around central supermassive black holes of active galactic nuclei (AGNs). It is usually used to estimate the masses of supermassive black holes. Although spectroscopic reverberation mapping has used to study dozens of AGN, spectroscopic monitoring campaign of large sample is expansive. Here, we present results of photometric reverberation mapping with medium-band photometry. We monitored five nearby AGN which were already studied with H-alpha emission line. Observation has been performed for ~3 months with ~3 days cadence using three medium-band filters installed in LSGT (Lee Sang Gak Telescope; 0.43m). We found 0.01-0.08 magnitude variations from differential photometry. Also time-lags between continuum light-curves and H-alpha emission line light-curves are found using JAVELIN software. The result shows that our study and previous studies are consistent within uncertainty range. In the near future, medium-band photometric reverberation mapping seems useful to study large AGN samples. We will present preliminary result of following study that report new time lag measurement of six AGNs in the similar way.Kim, Yongjung;Im, Myungshin;Jeon, Yiseul;Kim, Minjin;Pak, Soojong;Hyun, Minhee;Taak, Yoon Chan;Shin, Suhyun;Lim, Gu;Paek, Gregory S.H.;Paek, Insu;Jiang, Linhua;Choi, Changsu;Hong, Jueun;Ji, Tae-Geun;Jun, Hyunsung D.;Karouzos, Marios;Kim, Dohyeong;Kim, Duho;Kim, Jae-Woo;Kim, Ji Hoon;Lee, Hye-In;Lee, Seong-Kook;Park, Won-Kee;Yoon, Yongmin;Byeon, Seoyeon;Hwang, Sungyong;Kim, Joonho;Kim, Sophia;Park, Woojin 34.3
Faint z ~ 5 quasars with M1450 ~ -23 mag are known to be the potentially important contributors to the ultraviolet ionizing background in the post-reionization era. However, their number density has not been well determined, making it difficult to assess their role in the early ionization of the intergalactic medium (IGM). In this work, we present the updated results of our z ~ 5 quasar survey using the Infrared Medium-deep Survey (IMS), a near-infrared imaging survey covering an area of 85 square degrees. From our spectroscopic observations with the Gemini Multi-Object Spectrograph (GMOS) on the Gemini-South 8 m Telescope, we discovered eight new quasars at z ~ 5 with -26.1 ≤ M1450 ≤ -23.3. Combining our IMS faint quasars with the brighter Sloan Digital Sky Survey (SDSS) quasars, we derive, for the first time, the z ~ 5 quasar luminosity function (QLF) without any fixed parameters down to the magnitude limit of M1450 = -23 mag. We find that the faint-end slope of the QLF is very flat (-1.2) with a characteristic luminosity of -25.7 mag. The number density of z ~ 5 quasars from the QLF gives lower ionizing emissivity and ionizing photon density than those in previous works. These results imply that quasars are responsible for only 10-20% of the photons required to completely ionize the IGM at z ~ 5, disfavoring the idea that quasars alone could have ionized the IGM at z ~ 5.Since the discovery of SMBHs at z > 6, the growth spurt of a BH in a relatively short time—a few hundred Myr—has been a challenging topic for many observers and theorists. Super-Eddington accretion, major and minor merger have been compelling candidate machanisms to account for such growth. We introduce a passive scalar field to trace the infalling of circumgalactic gas clump onto high-z quasar. With the scalar field, we investigate e.g. where the most of the gas clump eventually reside in the host galaxy and how much gas is accreted onto the central massive black hole. In addition, we have studied the impact of thermal feedback of stars on the growth of black hole and the infalling gas. We will also discuss the future application of passive scalar field in e.g. minor and major mergers of high-z quasar.Submillimeter galaxies (SMGs) have played an important role in the understanding of galaxy evolution and cosmic star formation history at high redshift because they are known as being located at z ~ 2 and harbor a vigorous star formation. Therefore studying properties of SMGs can lead us to understand evolution of massive and actively star forming galaxies and distribution of cosmic star formation density. Recently we detected 548 SMGs near North Ecliptic Pole with JCMT/SCUBA-2 from the JCMT large program covering about 2 deg2 so far. To derive their physical parameters, we compiled a multi-wavelength photometry ranging from optical (0.3 ㎛) to submillimeter (850 ㎛) by cross-identifying counterparts at different wavelengths. In order to find counterparts, we used either VLA-1.4 GHz image and/or Spitzer/IRAC 3.6 ㎛, 4.5 ㎛ image. The number of SMGs with relatively robust counterparts is 349. In this talk, we present photometric redshifts, stellar mass, star formation rates, total infrared luminosity, and AGN fraction of these 349 SMGs derived through SED fitting analysis.Hyun, Minhee;Smail, Ian;Im, Myungshin;Windhorst, Roger A.;Jansen, Rolf A.;Wilmer, Christopher N.A.;Cotton, William D.;Fazio, Giovanni;Perley, Richard;Condon, James J.;Swinbank, Mark;Cohen, Seth;Lin, Li-Hwai;An, Fangxia;Shim, Hyunjin 35.3
The Time Domain Field is one of the future GTO program fields of JWST(JWST/GTO TDS), surveying about 14' diameter field at the North Eliptical Pole(NEP) with NIRCam/NIRISS. As a part of the multi-wavelength study of the field, we have obtained SCUBA-2 850㎛ mapping which reaches a depth of σrms = 0.9mJy/beam and detect 93 sources at S/N > 3.5 ― which are expected to be highly star-forming (SFR>400M◉/yr) galaxies at z ≳ 1.5-4 and pinpoint the location at <0. " 1 accuracy of 68 sub-mm sources by identifying VLA 3GHz radio counterparts. In this talk, we will introduce the SCUBA-2 JWST/GTO TDS project and the newly discovered sub-mm sources in this field.The progenitor of Type Ia supernovae (SNe Ia) is mainly believed to be a carbon/oxygen white dwarf (WD) with non-degenerate (single degenerate) or another WD companion (double degenerate). However, there is little observational evidence of their progenitor system. Recent studies suggest that shock-breakout cooling emission after the explosion can constrain the size of the progenitor system. To do so, we obtained a optical/Near-IR light curve of SN 2019ein, a normal but slightly sub-luminous type Ia supernova, from the very early phase using our high-cadence observation of Intensive Monitoring Survey of Nearby Galaxies (IMSNG). Assuming the expanding fireball model, the simple power-law fitting of the early part of the light curve gives power indices of 1.91 (B) and 2.09 (R) implying radioactive decay of 56Ni is the dominant energy source. By comparison with the expected light curve of the cooling emission, the early observation provides us an upper limit of the companion size of R∗≤1R⊙. This result suggests that we can exclude a large companion such as red giants, which is consistent with the previous study.Intensive Monitoring Survey of Nearby Galaxies (IMSNG) has been managed over 6 years. It aimed to constrain the progenitor system and explosion mechanism of SNe by detection of very early signal from shock heated emission. We have conducted monitoring observation of nearby bright galaxies those were carefully selected using global network of 1-m class telescopes. More than 20 SNe have occured in our target fields. As One of result of the survey, we present light curve analysis of type Ia SN 2018kp, which was discovered in NGC 3367. Based on photometric analysis, we calculated explosion parameters and set constraints of physical conditions of this supernova. We compared the results with theoretical model progenitor systems to find out which scenario is the most fitted to SN 2018kp case. Moreover, we estimate the distance to the galaxy and look into the relation between SNe and galactic physical parameters.Recent observation of the neutron star merger event, GW170817, through both gravitational wave (GW) and electromagnetic wave (EM) observations opened a new way of exploring the universe, namely, multi-messenger astronomy (MMA). One of the keys to the success of MMA is a rapid identification of EM counterpart. We will introduce GW follow-up observation project in Korea for hunting GW EM counterpart rapidly and its strategy for prioritization of GW source host galaxy candidates. Our method relies on recent simulation results regarding plausible properties of GW source host galaxies and the low latency localization map from LIGO/Virgo. We will show a test result for both binary neutron star merger events using previous event and describe observing strategy with our facilities for GW events during the ongoing LIGO/Virgo O3 run. Finally, we report the results of optical/NIR follow-up observation of GW190425, the first neutron.Cosmic-ray protons (CRp) are efficiently produced at starburst galaxies (SBGs), where the star formation rate (SFR) rate is high. In this talk, we present estimates of gamma-ray and neutrino emissions from nearby SBGs, M82, NGC253, and Arp220. Inside the starburst nucleus (SBN), CRp are accelerated at supernova remnant (SNR) shocks as well as at stellar wind (SW) termination shocks, and their transport is governed by the advection due to starburst-driven wind and diffusion mediated by turbulence. We here model the momentum distributions of SNR and SW-produced CRp with single or a double power-law forms. We also employ two different diffusion models, where CRp are resonantly scattered off large-scale turbulence in SBN or self-excited waves driven by CR streaming instability. We then calculate gamma-ray/neutrino fluxes. The observed gamma-ray fluxes by Fermi-LAT, Veritas, and H.E.S.S are well reproduced with double power-law distribution for SNR-produced CRp and the CRp diffusion by self-excited turbulence. The estimated neutrino fluxes are <~10-3 of the atmospheric neutrino flux in the energy range of Eneutrino <~100 GeV and <~10-1 of the IceCube point source sensitivity in the energy range of Eneutrino >~60 TeV.We study the structures and dynamics of flows generated by ultra-relativistic jets on kpc scales through three-dimensional relativistic hydrodynamics (RHD) simulations. We employ a newly developed RHD code, equipped with the WENO-Z reconstruction, the SSPRK time discretization, and an equation of state that closely approximates the single-component perfect gas in relativistic regime. Exploring a set of models with various parameters, we confirm that the well-known Fanaroff-Riley dichotomy is primarily determined by the jet power, whereas the morphology of simulated jets also depends on the secondary parameters such as the momentum injection rate and the ratio of the jet to background pressure. Utilizing high resolution capabilities of the newly developed code, we examine in detail the dynamical properties of complex flows in different parts of jet-produced structures, and present the statistics of nonlinear dynamics such as shock, shear, and turbulence.Yi, Sukyoung K.;Park, Min-Jung;Peirani, Sebastien;Pichon, Christophe;Dubois, Yohan;Choi, Hoseung;Devriendt, Julien;Kimm, Taysun;Kaviraj, Sugata;Kraljic, Katarina;Volonteri, Marta 37.3
Ever since thick disk was proposed to explain the vertical distribution of the Milky Way disk stars, its origin has been a recurrent question. We aim to answer this question by inspecting 19 disk galaxies with stellar mass greater than 10^10 solar mass in recent cosmological high-resolution (>34 pc) zoom-in simulations: Galactica and New Horizon. The thin and thick disks are reproduced by the simulations with scale heights and luminosity ratios that are in reasonable agreement with observations. When we spatially classify the disk stars into thin and thick disks by their heights from the galactic plane, the "thick" disk stars are older, less metal-rich, kinematically hotter, and higher in accreted star fraction than the "thin" disk counterparts. However, we found that the the thick disk stars were spatially and kinematically thinner when they were born. Indeed, a large fraction of thick disk stars was born near the galactic plane at earlier times and get heated with time, eventually occupying high altitudes and exhibiting different population properties compared to the thin-disk stars. In conclusion, from our simulations, the thin and thick disk components are not entirely distinct at birth, but rather a result of the time evolution of the stars born in the main disk of the galaxy. (excerpted from the abstract of the upcoming paper submitted to Astrophysical Journal: Park, M.-J., Yi, S.K. et al. 2020)Recent integral field spectroscopy observations have found that about 11% of galaxies show star-gas misalignment. The misalignment possibly results from external effects such as gas accretion, interaction with other objects, and other environmental effects, hence providing clues to these effects. We explore the properties of misaligned galaxies using Horizon-AGN, a large-volume cosmological simulation, and compare the result with the result of the Sydney-AAO Multi-object integral field spectrograph (SAMI) Galaxy Survey. Horizon-AGN can match the overall misalignment fraction and reproduces the distribution of misalignment angles found by observations surprisingly closely. The misalignment fraction is found to be highly correlated with galaxy morphology both in observations and in the simulation: early-type galaxies are substantially more frequently misaligned than late-type galaxies. The gas fraction is another important factor associated with misalignment in the sense that misalignment increases with decreasing gas fraction. However, there is a significant discrepancy between the SAMI and Horizon-AGN data in the misalignment fraction for the galaxies in dense (cluster) environments. We discuss possible origins of misalignment and disagreement. This presentation is mainly based on the published work Khim et al. 2020, ApJ, 894, 106 (17pp).Lee, Jaehyun;Shin, Jihey;Snaith, Owain N.;Kim, Yonghwi;Few, C. Gareth;Devriendt, Julien;Dubois, Yohan;Cox, Leah M.;Hong, Sungwook E.;Kwon, Oh-Kyoung;Park, Chan;Pichon, Christophe;Kim, Juhan;Gibson, Brad K.;Park, Changbom 38.2
Horizon Run 5 (HR5) is a cosmological hydrodynamical simulation which captures the properties of the Universe on a Gpc scale while achieving a resolution of 1 kpc. This enormous dynamic range allows us to simultaneously capture the physics of the cosmic web on very large scales and account for the formation and evolution of dwarf galaxies on much smaller scales. Inside the simulation box. we zoom-in on a high-resolution cuboid region with a volume of 1049 × 114 × 114 Mpc3. The subgrid physics chosen to model galaxy formation includes radiative heating/cooling, reionization, star formation, supernova feedback, chemical evolution tracking the enrichment of oxygen and iron, the growth of supermassive black holes and feedback from active galactic nuclei (AGN) in the form of a dual jet-heating mode. For this simulation we implemented a hybrid MPI-OpenMP version of the RAMSES code, specifically targeted for modern many-core many thread parallel architectures. For the post-processing, we extended the Friends-of-Friend (FoF) algorithm and developed a new galaxy finder to analyse the large outputs of HR5. The simulation successfully reproduces many observations, such as the cosmic star formation history, connectivity of galaxy distribution and stellar mass functions. The simulation also indicates that hydrodynamical effects on small scales impact galaxy clustering up to very large scales near and beyond the baryonic acoustic oscillation (BAO) scale. Hence, caution should be taken when using that scale as a cosmic standard ruler: one needs to carefully understand the corresponding biases. The simulation is expected to be an invaluable asset for the interpretation of upcoming deep surveys of the Universe.We examine how the mass assembly of central galaxies depends on their location in the cosmic web. The HORIZON-AGN simulation is analysed at z~2 using the DISPERSE code to extract multi-scale cosmic filaments. We find that the dependency of galaxy properties on large-scale environment is mostly inherited from the (large-scale) environmental dependency of their host halo mass. When adopting a residual analysis that removes the host halo mass effect, we detect a direct and non-negligible influence of cosmic filaments. Proximity to filaments enhances the build-up of stellar mass, a result in agreement with previous studies. However, our multi-scale analysis also reveals that, at the edge of filaments, star formation is suppressed. In addition, we find clues for compaction of the stellar distribution at close proximity to filaments. We suggest that gas transfer from the outside to the inside of the haloes (where galaxies reside) becomes less efficient closer to filaments, due to high angular momentum supply at the vorticity-rich edge of filaments. This quenching mechanism may partly explain the larger fraction of passive galaxies in filaments, as inferred from observations at lower redshifts.Jeong, Woong-Seob;Yang, Yujin;Park, Sung-Joon;Pyo, Jeonghyun;Jo, Youngsoo;Kim, Il-Joong;Bang, Seungcheol 39.2
Based upon the previous heritage in the complete development of the infrared imaging spectrometer, NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1, we are participating in the NASA MIDEX mission (PI Institute: Caltech), the all-sky infrared spectro-photometric surveyor SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer). The SPHEREx will provide us the first all-sky infrared spectro-photometric data set to probe the origin of our Universe, to explore the origin and evolution of galaxies, and to explore whether planets around other stars could harbor life. After the SPEHREx have passed the PDR (Preliminary Design Review) on this September, the fabrication of flight hardware will be started soon. As an international partner, KASI takes part in the hardware development, the operation and the science for the SPHEREx. Here, we report the status of the SPHEREx project and the progress in the Korean participation.Lee, Jae-Jin;Kim, Hong Joo;Nam, Uk-Won;Park, Won-Kee;Shon, Jongdae;Kim, Soon-Wook;Kim, Jeong-Sook;Kang, Yong-Woo;Uhm, Z. Lucas;Kang, Sinchul;Im, Sang Hyeok;Kim, Sunghwan 39.3
For the space weather research, KASI (Korea Astronomy and Space Science Institute) is developing the SNIPE (Small-scale magNetospheric and Ionospheric Plasma Experiment) mission, which consists of four 6U CubeSats of ~10 kg. Besides of space weather research, the SNIPE mission has another astrophysical objective, detecting Gamma-Ray Bursts(GRB). By cross-correlating the light curves of the detected GRBs, the fleet shall be able to determine the time difference of the arriving signal between the satellites and thus determine the position of bright short bursts with an accuracy ~100'. To demonstrate the technology of the GRB observation, CSI gamma-ray detectors combined with GPS and IRIDIUM communication modules are placed on each SNIPE CubeSat. The time of each spacecraft is synchronized and when the GRB is detected, the light curve will be transferred to the Mission Operation Center (MOC) by IRIDIUM communication module. By measuring time difference of each GRB signals, the technology for localization of GRB will be proved. If the results show some possibilities, we can challenge the new astrophysical mission for investigating the origin of GRB.Jin, Ho;Kim, Khan-Hyuk;Lee, Seongwhan;Lee, Hyojeong;Seon, Daerac;Jung, Byungwook;Jang, Yunho;Park, Hyeonhu 40.1
The Korea Astronomy and Space Science Institute is participating as a South Korean partner in the Commercial Lunar Payload Services (CLPS)of NASA. In response, the Korea Astronomy and Space Science Institute is currently conducting basic research for the development of four candidate instrument payloads. The magnetic field instrument is one of them and it's scientific mission objective is the moon's surface magnetic field investigation. Therefore, the development requirement of the lunar surface magnetic field instrument were derived and the initial conceptual design was started. The magnetic field instrument has a 1.2 meter boom which has two three-axis fluxgate magnetometer sensors and one gyro sensor to get a attitude information of the boom. The concept of measuring the lunar surface magnetic field will carry out using multiple sensors by placing semiconductor type magnetic field sensors inside the electric box including boom mounted fluxgate sensors. In order to overcome the very short development period, we will use the KPLO (Korean Lunar Pathfinder Orbiter) magnetometer design and parts to improve reliabilities for this instrument. In this presentation, we introduce the instrument requirements and conceptual design for the Lunar surface magnetic field instruments.500kg급 차세대중형위성은 공공분야 위성 수요에 효과적으로 대응하고, 국내 위성산업 저변 확대 및 산업체 육성을 위한 사업으로 개발되고 있다. 국내 산업체에서 개발되는 표준 위성 플랫폼이 적용될 예정인 차세대중형위성3호는 우주과학/기술검증용 위성으로, 특히 한국형발사체에 의해 2023년 발사된다는 점이 특별하다. 본 발표에서는 차세대 중형위성 3호에 제안한 우주망원경 UVOMPIS (UV-Optical Multiband Polarizing Imager System)에 대한 개념 설계 결과 및 과학 임무에 대한 소개를 통해 국내 학계와 산업계의 협력과 관심을 유도하고자 한다.한국천문연구원은 천문우주분야의 과학임무 탑재체 개발을 주도적으로 수행해오고 있다. 과학기술위성1호 주탑재체 원자외선영상분광기 FIMS 개발, 과학기술위성3호 주탑재체 다목적적외선영상시스템 MIRIS 개발, 차세대소형위성1호 주탑재체 근적외선영상분광기 NISS 개발을 수행하였고, 현재는 NASA와 국제협력으로 SPHEREx 우주망원경을 개발하고 있다. 이러한 개발 과정을 거치면서 주경 20cm 이하의 소형 탑재체 과학임무 한계와 더불어 연구 현장에서 더 큰 우주망원경의 수요가 제기되었고, 현재의 국가우주개발 중장기계획에도 2030년대 한국형 우주망원경을 포함하게 되었다. 이러한 일정에 발맞추어 한국천문연구원은 2030년대 한국형 우주망원경 독자 운영을 대비하기 위해서 2020년 1월부터 주요 사업으로 한국형 우주망원경 개발을 위한 기획연구를 시작하였다. 이 기획연구는 2년 동안 수행할 예정이며, 이 기획연구를 통해서 학계의 과학임무 요구사항을 사전에 충분히 조사하고, 국내외 산학연 전문가의 의견들을 종합 수렴하여 선도적인 과학 연구를 수행할 수 있는 우주망원경의 기본 제원을 확정할 예정이다. 이 발표에서는 이러한 기획연구의 세부 활동을 공유하고 보고하고자 한다.Ahn, Hojae;Mo, Gyuchan;Jung, Hyeonwoo;Choi, Junwhan;Kwon, Dou Yoon;Lee, Minseon;Kim, Dohoon;Lee, Sumin;Park, Woojin;Lee, Ho;Park, Kiehyun;Kim, Hyunjong;Pak, Soojong 40.4
Kyung Hee university invented the Transformable Reflective Telescope (TRT) for optical experiment and education. The TRT kit can transform into three optical configurations from Newtonian to Cassegrain to Gregorian by exchanging the secondary mirror. We designed the Ebert-Fastie spectrograph as an extension of the TRT kit. The primary mirror of the TRT kit serves as both collimator and camera lens, and the reflective grating as the dispersing element is placed along the optical axis of the primary mirror. We designed and fabricated the grating holder and the source units using 3D printer. Baffle was also fabricated to suppress the stray light, which was reduced by 83%. The spectrograph can observe the optical wavelength range (4000Å~7000Å). Measured resolving power (R=λ/Δλ) was ~700 with slit width of 0.18mm. The spectrograph is optimized for f/24, and the spectral pixel scale is 0.49Å/pixel with Canon 550D detector. We present the sample spectra of discharged Ne, Ar and Kr gases. The flexible setting and high performance make this spectrograph a useful tool for education and experiment.Yun, Hyeong-Sik;Lee, Jeong-Eun;Evans, Neal J. II;Offner, Stella;Heyer, Mark H.;Choi, Yunhee;Lee, Yong-Hee;Baek, Giseon;Choi, Minho;Kang, Hyunwoo;Tatematsu, Ken'ichi;Lee, Seokho;Yang, Yao-Lun;Gaches, Brandt;Chen, How-Huan 41.1
Different molecular lines trace different physical environments (with various densities and temperatures) within molecular clouds (MCs). Therefore, multimolecular line observations are crucial to study the physical and chemical structures of MCs. We observed the Orion A and Ophiuchus clouds in six different molecular lines as a Taeduk Radio Astronomy Observatory Key Science Program (TRAO-KSP), "mapping Turbulent properties In star-forming MolEcular clouds down to the Sonic scale" (TIMES; PI: Jeong-Eun Lee). Here, we investigate the characteristic relations between the observed lines by performing the Principal Component Analysis (PCA). We also investigate the correlation between the line intensity distributions and the physical parameters, such as the gas column density and dust temperature. Finally, we will discuss how the correlations among different chemical tracers vary with the star formation environments.Understanding how the filamentary structure plays a role in the formation of the prestellar cores and stars is a key issue to challenge. We have observed two prestellar cores in surrounding filamentary environments in 13CO, C180 (3-2) and HCO+ (4-3) molecular lines with the Heterodyne Array Receiver Program (HARP) of the James Clerk Maxwell Telescope (JCMT), in order to search for the evidence related to the possible flow motions along the filament and/or the radial accretion (or infalling motions) of gas material toward the dense cores from their surrounding filamentary cloud. In L1544, the velocity gradient of 1.6 km s-1 pc-1 toward the core was measured in a small branch of filament lying on a radial direction of main filament while no velocity gradient along the main axis of filament in both 13CO and C18O lines. In L694-2, we found the velocity gradient of 0.6 km s-1 pc-1 along the filament in only 13CO lines. The projected accretion rate of ~6 M◉ Myr-1 was estimated in both cases. The infall (or radially contracting) velocity of gas material was measured ~0.16 km s-1 in both 13CO and HCO+ lines and in both L1544 and L694-2, which leads to estimate a mass infall rate of ~20 M◉ Myr-1. Our analysis suggests that our targets are at a stage where the gravitational contraction dominates the mass accretion through the surrounding filamentary cloud. This is consistent with the fact that our targets are highly evolved prestellar cores on a verge of star formation. More detailed results will be presented at the meeting.Filamentary structures pervade the whole kind of molecular clouds from low- to high-mass star-forming clouds, and the non-star-forming clouds. It is supposed to be a prerequisite stage of star formation, and hence how filaments and dense cores form is one of the critical questions in the early star formation study. We investigated the dynamics and chemistry of dense cores in IC5146 using TRAO FUNS (TRAO Survey of the nearby Filamentary molecular clouds, the Universal Nursery of Stars) data. In addition, we performed polarization observation using JCMT Pol-2 polarimetry to investigate the magnetic field morphology within a core-scale. In the presentation, we will present the result of TRAO FUNS and JCMT/Pol2 observation toward the filaments and dense cores in the IC5146. We aim to reveal the roles of gravity, turbulence, and magnetic field in the formation of dense cores in the western hub-filament structure of IC5146.We report on multi-wavelength observations of AA Ori, a Young Stellar Object in Orion-A star-forming region. AA Ori is known to have a pre-transitional disk based on infrared observations including Spitzer/IRS data. We construct its broadband spectral energy distribution (SED) by not only taking data in the optical and IR region but also including Herschel/PACS, JCMT/SCUBA, and SMA observational data. We use the Monte Carlo radiative transfer code (RADMC-3D) to reconstruct the SED with a viscous accretion disk model initialized by a radially continuous disk and finally having an inner and outer dusty disk separated by a dust-depleted radial gap. By comparing the model SEDs with different configurations of disk parameters, we discuss the limits to find a single solution of model parameters to fit the data. We suggest that some models with a modified inner disk surface density gradient and some degree of dust depletion in the inner disk can explain the AA Ori's SED, from which we infer that the inner disk of AA Ori has evolved. We present that model configurations of a pre-transitional disk with a large gap extended to 60-80 AU in a settled dusty disk of a few hundred AU size with a high inclination angle (~60°) also create model SEDs close to the observed one. To distinguish whether the disk has a just-opened narrow gap or a large gap, with an altered surface density of the inner disk extended to 10 AU, we suggest a further investigation of AA Ori with high angular resolution observations.We investigate the observational properties of Wolf-Rayet stars, suggest the constraint of their mass-loss rate and apply our results to the observed progenitor candidates of Type Ib/Ic supernovae (iPTF13bvn and SN 2017ein). For this purpose, we adopt the WR star models with various mass-loss rates and wind terminal velocities. We obtain the high resolution spectra of those models at the pre-supernova phase using the radiative transfer code CMFGEN. We verify the optically faint property of SN Ic progenitors and show that the optical faintness is mainly originated by the high effective temperature at the photosphere. We also show that a simple analytic model for WR winds using a constant opacity can roughly predict the photospheric parameters. We show that the change of the mass-loss rate and the terminal wind velocity critically affects the optical luminosity. We find the optical luminosities of SN Ic progenitor models with our fiducial mass-loss rate prescription are fainter than the detection limits. We also suggest the mass-loss rate of WR stars may not exceed 2 times of our fiducial value by comparing our predictions with the detection limit of SN Ib/Ic progenitors. The directly observed progenitor candidate of iPTF13bvn can be explained by our SN Ib progenitor models. We find that the SN 2017ein progenitor candidate is too bright and too blue to be a SN Ic progenitor.The hydrogen-rich envelope mass of a dying massive star is the key factor that determines the type and properties of the resulting supernova. Emulating wind-driven mass loss of single stars with the MESA(Modules for Experiments in Stellar Astrophysics) stellar evolution code, we made a grid of models for a large parameter space of initial mass (12 M⊙ to 30M⊙), metallicity (solar, LMC and SMC), hydrogen envelope mass (0.01M⊙ to 10M⊙) for progenitor stars in their final step of evolution. Our results suggest the final luminosity of the progenitor is largely determined by the initial mass, which means there is luminosity degeneracy for stars with the same initial mass but with different hydrogen-rich envelope masses. Since we can break this degeneracy by correcting luminosity with surface gravity (spectroscopic HR diagram), we can infer the exact mass property of an observed progenitor. The surface temperature drastically varies near the envelope mass of ~0.1M⊙ and surface temperature of ~10000 K, where the demarcation between the hydrogen-rich envelope and the helium core lies, which explains the rarity of 'white' supergiants. There also exists a discontinuity in the chemical composition of the progenitor envelope around this critical hydrogen-rich envelope mass of ~0.1 M⊙, which can be tested in future observations of "flash spectroscopy" of supernovae.Koo, Bon-Chul;Kim, Hyun-Jeong;Oh, Heeyoung;Raymond, John C.;Yoon, Sung-Chul;Lee, Yong-Hyun;Jaffe, Daniel T. 43.1
Cassiopeia A (Cas A) is a young supernova remnant (SNR) where we observe the interaction of SNR blast wave with circumstellar medium. From the early optical studies, dense, slowly-moving, N-rich "quasi-stationary flocculi" (QSF) have been known. These are probably dense CNO-processed circumstellar knots that have been engulfed by the SNR blast wave. We have carried out near-infrared, high-resolution (R=45,000) spectroscopic observations of ~40 QSF, and here we present the result on a QSF knot (hereafter 'Knot 24') near the SNR boundary of Cas A. The average [Fe II] 1.644 um spectrum of Knot 24 has a remarkable shape with a narrow (~8 km/s) line superposed on the broad (~200 km/s) line emitted from shocked gas. The spatial morphology and the line parameters indicate that Knot 24 has been partially destroyed by a shock wave and that the narrow line is emitted from the unshocked material heated/ionized by the shock radiation. This is the first detection of the emission from the pristine circumstellar material of the Cas A supernova progenitor. We also detected H Br gamma and other [Fe II] lines corresponding to the narrow [Fe II] 1.644 um line. For the main clump where we can clearly identify the shock emission associated with the unshocked material, we analyze the observed line ratios using a shock model that includes radiative precursor. The analysis indicates that the majority of Fe in the unshocked material is in the gas phase, not depleted onto dust grains as in the general interstellar medium. We discuss the non-depletion of Fe in QSF and its implications on the immediate progenitor of the Cas A supernova.We have carried out high-resolution near-infrared (NIR) spectroscopic observations toward 16 Galactic supernova remnants (SNRs) showing strong H2 emission features. A dozen bright H2 emission lines are clearly detected for individual SNRs, and we have measured their central velocities, line widths, and fluxes. For all SNRs except one (G9.9-0.8), the H2 line ratios are well consistent with that of thermal excitation at T~2000 K and their line widths are broader than ~10 km s-1, indicating that the H2 emission lines are most likely from shock-excited gas and therefore that they are physically associated with the remnants. The kinematic distances to the 15 SNRs are derived from the central velocities of the H2 lines using a Galactic rotation model. We derive for the first time the kinematic distances to four SNRs: G13.5-0.2, G16.0-0.5, G32.1-0.9, G33.2-0.6. Among the rest 11 SNRs, the central velocities of the H2 emission lines for six SNRs are well consistent (±5 km s-1) with those obtained in previous radio observations, while for the other five SNRs (G18.1-0.1, G18.9-1.1, Kes 69, 3C 396, W49B), they are significantly different. We discuss the velocity discrepancies in these five SNRs. In G9.9-0.8, the H2 emission shows non-thermal line ratios and very narrow line width (~4 km s-1), and we discuss its origin.Hα jets of cool chromospheric plasma are protruding into the solar corona 10-100 Mm above the photosphere. The driving mechanisms of Hα jets have been widely studied for decades. However, the detailed process is still elusive. We observed shock signatures moving along a dark jet using 1.6 meter Goode Solar Telescope at Big Bear Solar Observatory. The first shock front of the jet shows sharp --- when it moves upward, while fuzzy and granulated when it moves downward. The jet itself extends upward when the second shock front of the jet reaches the top of the jet. We find abrupt EUV brightenings when the second shock front collides with the edge of the jet. The third front and the fouth front quasi-periodically. These phenomena might be the signs of the rebound shock waves triggered by p-mode wave leakages at the bottom of the jets. Our observation suggests that the jet can be triggered by the rebound shock waves generated by the p-mode waves leaked at the bottom of the jets.Kim, Yeon-Han;Choi, Seonghwan;Bong, Su-Chan;Cho, Kyungsuk;Park, Young-Deuk;Newmark, Jeffrey;Gopalswamy, Nat.;Yashiro, Seiji;Reginald, Nelson 44.2
The Korea Astronomy and Space Science Institute (KASI) has been collaborating with the NASA Goddard Space Flight Center (GSFC), to install a diagnostic coronagraph on the International Space Station (ISS). The coronagraph is designed to obtain simultaneous measurements of electron density, temperature, and velocity using multiple filters in the 3-10 Rs range. In 2019, we developed a new coronagraph and launched it on a stratospheric balloon (BITSE) from Fort Sumner, New Mexico in USA. As the next step, the coronagraph will be further developed, installed and operated on the ISS (CODEX) in 2023 to understand the physical conditions in the solar wind acceleration region, and enable and validate the next generation space weather models. In this presentation, we will report recent progress and introduce future plan.Sunspot substructure is an important subject to explain their stability and energy transport. Previous studies suggested two substructure models, monolithic and spaghetti model, but no clear evidence has been found supporting a particular model. To obtain the clue of the sunspot substructure the IRIS Mg II 2796Å slit-jaw images (SJI) were examined. The Mg II images formed in the chromosphere show bright patches inside umbrae which are regarded as an observational signature of upward propagating slow magnetohydrodynamic (MHD) waves. The slow MHD waves are expected to be generated by convective motion below the photosphere. By tracking the motion of the bright patches it is possible to estimate the locations of oscillation centers that correspond to the occurrence position of the convections. I investigated the spatial distribution of the oscillation center in a merging sunspot and found it is randomly distributed. It implies that the occurrence rate of the convective motion inside the sunspot is not much different from that of between the two sunspots, and supports the spaghetti model as the sunspot substructure.The solar chromosphere can be observed well through strong absorption lines. We infer the physical parameters of chromospheric plasmas from these lines using a multilayer spectral inversion. This is a new technique of spectral inversion. We assume that the atmosphere consists of a finite number of layers. In each layer the absorption profile is constant and the source function is allowed to vary with optical depth. Specifically, we consider a three-layer model of radiative transfer where the lowest layer is identified with the photosphere and the two upper layers are identified with the chromosphere. This three-layer model is fully specified by 13 parameters. Four parameters can be fixed to prescribed values, and one parameter can be determined from the analysis of a satellite photospheric line. The remaining eight parameters are determined from a constrained least-squares fitting. We applied the multilayer spectral inversion to the spectral data of the Hα and the Ca II 854.21 nm lines taken in a quiet region by the Fast Imaging Solar Spectrograph (FISS) of the Goode Solar Telescope (GST). We find that our model successfully fits most of the observed profiles and produces regular maps of the model parameters. We conclude that our multilayer inversion is useful to infer chromospheric plasma parameters on the Sun.Lim, Eun-Kyung;Yang, Heesu;Yurchyshyn, Vasyl;Chae, Jongchul;Song, Donguk;Madjarska1, Maria S. 45.1
Light bridges (LBs) are relatively bright structures that divide sunspot umbrae into two or more parts. Chromospheric LBs are known to be associated with various activities including fan-shaped jet-like ejections and brightenings. Although magnetic reconnection is frequently suggested to be responsible for such activities, not many studies presented firm evidence to support the scenario. We carry out magnetic field measurements and imaging spectroscopy of a LB where fan-shaped jet-like ejections occur with co-spatial brightenings at their footpoints. We study their fine photospheric structures and magnetic field changes using TiO images, Near-InfraRed Imaging Spectropolarimeter data, and Hα data taken by the 1.6 m Goode Solar Telescope. As a result, we detect magnetic flux emergence in the LB that is of opposite polarity to that of the sunspot. The new flux cancels with the pre-existing flux at a rate of 5.6×1018 Mx hr-1. Both recurrent jet-like ejections and their footpoint brightenings are initiated at the vicinity of the magnetic cancellation, and show apparent horizontal extension along the LB at a projected speed of 4.3 km s-1 to form the fan-shaped appearance. Based on these observations, we suggest that the fan-shaped ejections may have resulted due to slipping reconnection between the new flux emerging in the LB and the ambient sunspot field.Various processes, such as space weathering and granular convection, are occurring on asteroids' surfaces. Estimation of the surface exposure timescale is essential for understanding these processes. The Hayabusa mission target asteroid, (25143) Itokawa (Sq-type) is the only asteroid whose age is estimated from remote sensing observations as well as sample analyses in laboratories. There is, however, an unignorable discrepancy between the timescale derived from these different techniques. The ages estimated based on the solar flare track density and the weathered rim thickness of regolith samples range between 102 and 104 years [1][2]. On the contrary, the ages estimated from the crater size distributions and the spectra cover from 106 to 107 years [3][4]. It is important to notice that there is a common drawback of both age estimation methods. Since the evidence of regolith migration is found on the surface of Itokawa [5], the surficial particles would be rejuvenated by granular convection. At the same time, it is expected that the erasure of craters by regolith migration would affect the crater size distribution. We propose a new technique to estimate surface exposure age, focusing on the bright mottles on the large boulders. Our technique is less prone to the granular convection. These mottles are expected to be formed by impacts of mm to cm-sized interplanetary particles. Together with the well-known flux model of interplanetary dust particles (e.g., Grün, 1985 [6]), we have investigated the timescale to form such mottles before they become dark materials again by the space weathering. In this work, we used three AMICA (Asteroid Multi-band Imaging Camera) v-band images. These images were taken on 2005 November 12 during the close approach to the asteroid. As a result, we found the surface exposure timescales of these boulders are an order of 106 years. In this meeting, we will introduce our data analysis technique and evaluate the consistency among previous research for a better understanding of the evolution of this near-Earth asteroid.Kim, Myung-Jin;Choi, Young-Jun;Yang, Hongu;Lee, Hee-Jae;Kim, Dong-Heun;JeongAhn, Youngmin;Roh, Dong-Goo;Moon, Hong-Kyu;Chang, Chan-Kao;Durech, Josef;Broz, Miroslav;Hanus, Josef;Masiero, Joseph;Mainzer, Amy;Bauer, James 46.1
DEEP-South (DEep Ecliptic Patrol of the Southern Sky) team will start the 2nd phase of KMTNet observation in Oct 2020. The DEEP-South observation mainly consists of three survey modes: (1) Activity survey (AS) that aims at finding active phenomena of small Solar System bodies. (2) Light curve survey (LS) targets to discover and characterize light variations of asteroids. And (3) Deep drilling survey (DS) focuses on the objects beyond the orbit of Jupiter (Centaurus and trans-Neptunian objects) as well as near Earth asteroids. For asteroid family (AF) studies and target of opportunity (TO) observations for urgent photometric follow-up, targeted mode will also be used. DEEP-South team is awarded 7.0% of the telescope time at each site every year from Oct 2020 to Sep 2023 in the 2nd phase of KMTNet operation which corresponds to about 75 full nights a year for the network. In this presentation, we will introduce our survey strategy and observation plan.Yang, Hongu;Lee, Hee-Jae;Lee, Mingyeong;Kim, Dong-Heun;Ishiguro, Masateru;Moon, Hong-Kyu;JeongAhn, Youngmin;Choi, Young-Jun 46.2
Dust ejection activities have been discovered from a few tens of asteroids since the first confirmation in 2006. Those objects are known as active asteroids. They provide good observational chances to study ongoing phenomena in the solar system such as sublimation of icy volatiles, mutual collisions among asteroids, rotational disintegrations, thermal fatigue, etc. Although dust ejection mechanisms of individual cases have been investigated through observations, the frequencies of the events and their connection to the overall evolutionary budget of the solar system have not yet been studied thoroughly, mainly because previous studies were based on serendipitous discoveries without any systematic surveys of these objects. In this work, we made wide-field monitoring observations of asteroids using Korea Microlensing Telescope Network (KMTNet) during the 2018/2019 winter season. Among 3,644 asteroids in the field-of-view, we detected nine candidates of brightness enhancements which we suspect as possible activities. It is still possible that some of those brightness increases have caused by long-term rotations. However, our observed frequency and brightness enhancements size-frequency distribution agrees with the expectations from impacts with decimeter sized objects, when the main belt objects size-frequency distribution observed down to decameter sized bodies are extrapolated to decimeter size.Lee, Hee-Jae;Yang, Hongu;Kim, Dong-Heun;Kim, Myung-Jin;Moon, Hong-Kyu;Kim, Chun-Hwey;Choi, Young-Jun 46.3
Variations in the brightness of asteroids are caused by their spins, irregular shapes and companions. Thus, in principle, the spin state and shape model of a single object or, a combined model of spins, shapes and mutual orbit of a multiple components can be constructed from the analysis of light curves obtained from the time-series photometry. Using ground- and space-based facilities, a number of time-series photometric observations of asteroids have been conducted to find the possible causes of their light variations. Nonetheless, only about 2% of the known asteroids have been confirmed for their rotation periods. Therefore, a follow-on systematic photometric survey of asteroids is essential. We started an asteroid light curve survey for this purpose using Korea Microlensing Telescope Network (KMTNet) during 199 nights between the second half of 2019 and the first half of 2020. We monitored within a 2° × 14° region of the sky per each night with 25 min cadences. In order to observe as many asteroids as possible with a single exposure, we mostly focus on the ecliptic plane. In our survey, 25,925 asteroids were observed and about 8,000 of them were confirmed for their rotation periods. In addition, using KMTNet's 24-hour continuous monitoring, we collected many composite light curves of slow rotating asteroids that were rarely obtained with previous observations. In this presentation, we will introduce the typical light curves of asteroids obtained from our survey and present a statistical analysis of spin states and shapes of the asteroids from this study.Multi-band photometry provides an advantage in being able to perform taxonomic classification analysis on a large number of asteroids in a much shorter period of time than spectroscopy. We observed main-belt asteroids using Korea Microlensing Telescope Network (KMTNet) in CTIO during the summer seasons in the southern hemisphere, mostly in December 2015, 2016 and 2017 with two visible photometric systems, SDSS (g, r, i, and z), and Johnson-Cousins (B, V, R, and I). Targets were selected for the asteroids which had already been classified based on Bus-Binzel taxonomy (Bus & Binzel, 2002) and DeMeo taxonomy (DeMeo et al. 2009). Not only the targets but also numerous serendipitously observed asteroids were identified. In summary, 6817 and 5456 known objects, including 307 and 233 already classified asteroids were observed with SDSS and Johnson-Cousins systems, respectively. Using principal component analysis, the three major asteroid complexes and a class, S-, C-, and X-complexes and V class are found to be well separated in the principal component plane (spectral slope and 1 micron absorption depth) with both filter systems. We will present and discuss the results of our newly proposed three-dimensional color taxonomy for asteroids using the whole dataset (Roh et al., to be submitted).The Experiment to Detect the Global EoR Signature (EDGES) has probed the status of the early Universe through the global 21cm observation. The claimed (brightness temperature) of ~ 500 mK absorption dip at z~17 against the continuum background cannot be explained in the standard LambdaCDM framework. In the meantime, the Planck 2018 Legacy Data, especially the E-mode polarization power spectrum, puts rather strong constraints on the high-redshift reionization process. We show how these two observational contraints can be accomodated in a series of reionization scenarios, with a special focus on the strongly self-regulated reionization by first stars.I will present the Sejong Suite, an extensive collection of state-of-the-art high-resolution cosmological hydrodynamical simulations spanning a variety of cosmological and astrophysical parameters, primarily developed for modeling the Lyman-Alpha forest. Adopting a particle-based implementation, we follow the evolution of gas, dark matter (cold and warm), massive neutrinos, and dark radiation, and consider several combinations of box sizes and number of particles. Noticeably, for the first time, we simulate extended mixed scenarios describing the combined effects of warm dark matter, neutrinos, and dark radiation, modeled consistently by taking into account the neutrino mass splitting. Along the way, I will also highlight some new results focused on the matter and flux statistics.The cosmological constant is accountable for the accelerated expansion of our Universe. Observational data have provided a tight constraint on the cosmic star formation history from z = 8 to the present. What happens to the star formation rate beyond z=0? I will discuss the star formation rates, along with the properties of the intergalactic mediumfrom our suite of simulations into the future. Since Lambda becomes dominant in the future of our universe, I further simulate counter-factual universes to assign anthropic weights to each universe within the multiverse setting. I will argue that using the asymptotic star formation efficiency as weights, we almost double previous estimates of observers living in universes similar to ours. The expected value of the energy density of Lambda is also closer to the observed value. I will also discuss potential future works to improve the applicability of the anthropic reasoning of the cosmological constant.We present a new void definition that connects voids with clusters, the high-density counterpart. We use a pair of ΛCDM simulations whose initial density fields are sign inverted versions to each other, and study the relation between the effective void volume and the corresponding cluster mass. Massive cluster halos (M ≥ 1013M⊙/h) are identified in one simulation at z=0 by linking dark matter particles. The corresponding void to each cluster is defined in the other simulation as the region occupied by the member particles of the cluster. We find a universal functional form of density profiles at z=0 and 1. We also find a power-law relation between the void effective radius and the corresponding cluster mass. Based on these findings, we identify cluster-counterpart voids directly from a density field without using the pair information by utilizing three parameters such as the smoothing scale, density threshold, and minimum core fraction. We identified voids corresponding to clusters more massive than M ≥ 3 × 1014M⊙/h at approximately 70-74 \% level of completeness and reliability. Our results suggest that we can detect voids comparable to clusters of a particular mass-scale.Using redshift-space distortion, I reconstruct the growth history as a smooth function using model independent methods. Assuming general relativity, I obtain the expansion history independently of the dark energy model, and test it to the supernovae data. The results are consistent with general relativity as gravity and the cosmological constant as dark energy, although interestingly negative dark energy densities are not ruled out by the data at z~0.7 to 1.We reconstruct the expansion history of the universe using type Ia supernovae (SN Ia) in a manner independent of any cosmological model assumptions. To do so, we implement a nonparametric iterative smoothing method on the Joint Light-curve Analysis (JLA) data while exploring the SN Ia light-curve hyperparameter space by Markov Chain Monte Carlo (MCMC) sampling. We test to see how the posteriors of these hyperparameters depend on cosmology, whether using different dark energy models or reconstructions shift these posteriors. Our constraints on the SN Ia light-curve hyperparameters from our model-independent analysis are very consistent with the constraints from using different parameterizations of the equation of state of dark energy, namely the flat ΛCDM cosmology, the Chevallier-Polarski-Linder model, and the Phenomenologically Emergent Dark Energy (PEDE) model. This implies that the distance moduli constructed from the JLA data are mostly independent of the cosmological models. We also studied that the possibility the light-curve parameters evolve with redshift and our results show consistency with no evolution. The reconstructed expansion history of the universe and dark energy properties also seem to be in good agreement with the expectations of the standard ΛCDM model. However, our results also indicate that the data still allow for considerable flexibility in the expansion history of the universe. This work is published in ApJ.In this talk, I will discuss a few different techniques to reconstruct different cosmological functions, such as the primordial power spectrum and the expansion history. These model independent techniques are useful because they can discover surprising results in a way that nested modeling cannot. For instance, we can use the modified Richardson Lucy algorithm to reconstruct a novel primordial power spectra from the Planck data that can resolve the "Hubble tension". This novel primordial power spectrum has regular oscillatory features that would be difficult to find using parametric methods. Further, we can use Gaussian process regression to reconstruct the expansion history of the Universe from low-redshift distance datasets. We can also this technique to test if these datasets are consistent with one another, which essentially allows for this technique to serve as a systematics finder.SDSS-III BOSS DR12 은하적색이동 탐사 자료 중 CMASS 표본을 사용하여 물질 분포에 대한 균일성 테스트를 수행하였다. 균일성의 비교 기준으로는 (i) 완전한 무작위 분포, (ii) Horizon Run 3 N-체 수치실험에서 얻은 헤일로 목록, 그리고 (iii) 물질 요동의 파워 스펙트럼과 로그정규분포를 가정해 얻은 모의 은하 목록을 사용하였다. 현재 관측된 영역에서 통계적으로 의미가 있는 가장 큰 규모인 300h-1Mpc까지 조사한 결과, 우리는 관측된 물질 분포가 무작위 분포와 비교하여 전혀 균일하지 않지만 우주론으로부터 구한 나머지 두 목록과는 부합함을 보였다. 우주의 균일 등방성을 제시하는 우주론 원리는 우주론의 이론적 전개에서 물질의 분포가 아닌 공간곡률에 적용된다. 지금 우주모형에서는 이 원리에서 벗어난 공간곡률의 정도가 충분히 작으므로 우주론 원리를 우주론에 적용하는 데 문제가 없다. 하지만 우리는 물질 분포가 균일 등방성에서 벗어난 정도가 상당함을 보였으며, 따라서 우주론 원리가 이론적 모형에 성공적으로 적용되지만 실제로 관측된 은하 분포에는 존재하지 않는다는 기존의 결론을 새로운 자료를 이용해 강화하였다.I will give an overview of the recent work in deriving cosmological constraints from deep learning methods applied to the large scale distribution of galaxies. I will specifically highlight the success of convolutional neural networks in linking the morphology of the large scale matter distribution to dark energy parameters and modified gravity scenarios.We introduce a novel method for reconstructing the projected matter distributions of galaxy clusters with weak-lensing (WL) data based on convolutional neural network (CNN). We control the noise level of the galaxy shear catalog such that it mimics the typical properties of the existing Subaru/Suprime-Cam WL observations of galaxy clusters. We find that our mass reconstruction based on multi-layered CNN with architectures of alternating convolution and trans-convolution filters significantly outperforms the traditional mass reconstruction methods.In this topic, I will introduce a recent work on reconstructing the cosmic density field based on the GAN. I will show the performance of the GAN compared to the traditional Unet architecture. I'd also like to discuss a 3-channels-based 2D datasets for the training to recover the 3D density field. Finally, I will present some performance tests based on the test datasets.The dark matter (DM) only simulations have been exploited to study e.g. the large scale structures and properties of a halo. In a baryon side, the high-resolution hydrodynamic simulation such as IllustrisTNG has helped extend the physics of gas along with stars and DM. However, the expansive computational cost of hydrodynamic simulations limits the size of a simulated universe whereas DM-only simulations can generate the universe of the cosmological horizon size approximately. I will introduce a pipeline to estimate baryonic properties of a galaxy inside a dark matter (DM) halo in DM-only simulations using a machine trained on high-resolution hydrodynamic simulations. An extremely randomized tree (ERT) algorithm is used together with multiple novel improvements such as a refined error function in machine training and two-stage learning. By applying our machine to the DM-only simulation of a large volume, I then validate the pipeline that rapidly generates a galaxy catalog from a DM halo catalog using the correlations the machine found in hydrodynamic simulations. I will discuss the benefits that machine-based approaches like this entail, as well as suggestions to raise the scientific potential of such approaches.We present deep UBVIc and Hα photometry for the young open cluster IC 1590 which is at the center of the HII region NGC 281. From Ha index, 39 Hα emission stars and 15 Hα emission candidates are selected. The reddening law toward IC 1590 is slightly abnormal (RV,cl = 3.6 ± 0.2). The distance modulus of IC 1590 obtained from the reddening-free (Q', QVλ) diagrams is 12.4 ± 0.1 mag (d = 3.02 ± 0.14 kpc), which is consistent with distance d = 2.91 ± 0.42 kpc from the parallax of Gaia DR2 catalogue within the error range. We also determined the age and mass function of IC 1590 using the stellar evolution models and PMS evolutionary tracks. The median age of PMS stars is 2.4 ± 2.2 Myr. The initial mass function (IMF) of IC 1590 is the Salpeter-type IMF with a slope of = -1.26 ± 0.14 for m > 1 M⊙ stars.We report our discovery of Raman-scattered He II λ6545 feature in young planetary nebulae NGC 6886 and NGC 6881 which indicates the existence of atomic hydrogen components. Considering sharply increasing cross-section of hydrogen atom near the resonance, Raman-scattered He II features are a useful diagnostic tool to investigate the distribution and kinematics of H I region in planetary nebulae. The high-resolution spectroscopic observation was carried out using BOES installed on the 1.8 m telescope of BOAO. We estimate the column density of H I region and its expansion velocity using our grid-based Monte-Carlo radiative transfer code. We assume that the H I region is uniformly distributed in spherical shell geometry with an opening angle and expands with constant speed. Our best-fit model is shown with the column density NHI = 3 × 1020 cm-2 and expansion speed vexp = 25 km s-1 with the opening angle ~ 25° for NGC 6886, and NHI = 4 × 1020 cm-2 and vexp = 30 km s-1 with the opening angle ~ 35° for NGC 6881. We present brief discussions on the late-stage of evolution of stars with mass > 3 M⊙.Lim, Beomdu;Hong, Jongsuk;Naze, Yael;Park, Byeong-Gon;Hwang, Narae;Lee, Jeong-Eun;Yun, Hyeong-Sik;Park, Sunkyung;Yi, Hee-Weon 51.1
The Rosette Nebula is the most actively star-forming region in the Monoceros OB2 association. This region hosts more than three stellar groups, including the most populous group NGC 2244 at the center of the region and the smaller stellar groups around the border of the H II bubble. To trace their formation process, we investigate the kinematic properties of these groups using the Gaia astrometric data and high-resolution spectra taken from observation with Hectochelle on MMT. The proper motions of stars in NGC 2244 show a pattern of radial expansion. The signature of cluster rotation is also detected from their radial velocities. On the other hand, the small groups appear to be physically associated with some clouds at the ridge of the H II region. Among them, the group near the eastern pillar-like gas structure shows the signature of feedback-driven star formation. In this presentation, we will further discuss the formation process and dynamical evolution of the stellar groups in the Rosette Nebula, based on the observation and results of N-body simulations.Luminous blue variables (LBVs) are massive evolved stars that show unpredictable photometric and spectral variation. It is generally assumed that they undergo one or more of large eruptions. We have obtained high dispersion NIR spectra of several LBVs with Immersion GRating INfrared Spectrometer (IGRINS). One notable feature in their IGRINS spectra is the existence of broad lines (~ a few hundred km/s) with unusual boxy profile. They are fluorescent lines of Fe II by Lyman α photons in the stellar wind. However, modeling of these lines with radiative transfer code CMFGEN predicts much weaker line strength. We propose that incorporating broadening of Lyman α line by scattering processes in dense wind can enhance the Fe II fluorescent lines. We further discuss how these Fe II fluorescent lines can be used to characterize massive LBV wind.We present the status of the development of a Markov Chain Monte Carlo (MCMC) parameter estimation (PE) pipeline for compact binary coalescences (CBCs) with the Japanese KAGRA gravitational-wave (GW) detector. The pipeline is included in the KAGRA Algorithm Library (KAGALI). Basic functionalities are benchmarked from the LIGO Algorithm Library (LALSuite) but the KAGRA MCMC PE pipeline will provide a simpler, memory-efficient pipeline to estimate physical parameters from gravitational waves emitted from compact binaries consisting of black holes or neutron stars. Applying inspiral-merge-ringdown and inspiral waveforms, we performed simulations of various black hole binaries, we performed the code sanity check and performance test. In this talk, we present the situation of GW observation with the Covid-19 pandemic. In addition to preliminary PE results with the KAGALI MCMC PE pipeline, we discuss how we can optimize a CBC PE pipeline toward the next observation run.We propose semi-analytic models for the electron momentum distribution in weak shocks that accounts for both in situ acceleration and reacceleration through diffusive shock acceleration (DSA). In the former case, a small fraction of incoming electrons is assumed to be reflected at the shock ramp and pre-accelerated to the so-called injection momentum, pinj, above which particles can diffuse across the shock transition and participate in the DSA process. This leads to the DSA power-law distribution extending from the smallest momentum of reflected electrons, pref, all the way to the cutoff momentum, peq, constrained by radiative cooling. In the latter case, fossil electrons, specified by a power-law spectrum with a cutoff, are assumed to be re-accelerated from pref up to peq via DSA. We show that, in the in situ acceleration model, the amplitude of radio synchrotron emission depends strongly on the shock Mach number, whereas it varies rather weakly in the re-acceleration model.At quasi-perpendicular shocks in the high- (=Pgas/Pmag~100) intracluster medium (ICM), various microinstabilities occur by the temperature anisotropies and/or drift motions of plasma. In the downstream, the Alfvén ion cyclotron instability (AIC) due to the ion temperature anisotropy (Ti⊥>Ti║) is triggered by shock-reflected ions, the whistler instability (WI) is driven by the electron temperature anisotropy (Te⊥>Te║) as a consequence of the shock compression of magnetic fields, and the mirror instability is generated due to the ion and/or electron temperature anisotropy. At the shock foot, the modified two stream instability (MTSI) is possibly excited by the cross-field drift between ions and electrons. In the upstream, electron firehose instability (EFI) is driven by the electron temperature anisotropy or the relative drift between incoming and reflected electrons. These microinstabilities play important roles in the particle acceleration in ICM shocks, so understanding of the microinstabilities and the resultant plasma waves is essential. In this study, based on a linear stability analysis, the basic properties of the microinstabilities in ICM shocks and the ion/electron scale fluctuations are described. We then discuss the implication of our work on the electron pre-acceleration in ICM shocks.천문학적 유체는 강하게 자화되어 있는 경우가 많은데, 이러한 강한 자기장을 얻는 한 방법이 난류에 의한 자기장의 증폭이다. 플라즈마 효과나 기타의 이유로 약한 씨앗 자기장이 유체에 생길 경우, 난류는 이 씨앗 자기장을 매우 효과적으로 증폭시킬 수가 있다. 이 과정을 난류 다이너모라 하는데, 난류 다이너모는 주로 비압축성 난류 구동력을 사용하여 연구해 오고 있다. 비압축성 구동력을 사용할 때의 난류 다이너모 과정은 비교적 잘 규명되어 있다. 기존의 연구 결과에 의하면, 자기장의 세기는 지수 함수적 성장을 거친 후 선형적 성장 단계를 겪는다. 이후, 자기장의 에너지 밀도가 난류의 에너지 밀도와 비슷해지면 자기장은 더 이상 성장하지 못하고 포화 상태에 접어든다. 결론적으로 난류는 자기장이 동력학적으로 중요한 수준까지 증폭을 시킬 수 있다. 압축성 난류 구동력을 사용한 난류 다이너모 연구도 일부 존재하는데, 기존의 연구 결과에 의하면 다이너모 효과가 비압축성 구동력의 경우보다 비효율적이다. 본 연구에서는 압축성 구동력을 사용하여 난류 다이너모를 체계적으로 연구하였다. 특히 압축성 구동력과 비압축성 구동력이 난류 다이너모 효과에 어떤 차이를 주는지 체계적으로 비교하였다.It is less well known that the properties, especially the mass accretion rate, of accretion flow are affected by the angular momentum of accreting gas. Park (2009) found that the mass accretion rate \dot{m}, mass accretion rate in units of Bondi accretion rate, is inversely proportional to the angular momentum of gas λ, at the Bondi radius where gas sound speed is equal to the free-fall velocity and proportional to the viscosity parameter α, and also Narayan & Fabian (2011) found a similar relation, but the dependence of the mass accretion rate of the gas angular momentum is much weaker. In this work, we investigate the global solutions for the rotating Bondi flow, i.e., polytropic flow accreting via viscosity, for various accretion parameters and the dependence of the mass accretion rate on the physical characteristics of gas. We set the outer boundary at various radius r_{out}=10^3~10^5 r_{Sch}, where r_{Sch} is the Schwarzschild radius of the black hole. For a small Bondi radius, the mass accretion rate changes steeply, as the angular momentum changes, and for a large Bondi radius, the mass accretion rate changes gradually. When the accreting gas has a near or super Keplerian rotation, we confirm that the relation between the mass accretion rate and angular momentum is roughly independent of Bondi radius as shown in Park (2009). We find that \dot{m} is determined by the gas angular momentum at the Bondi radius in units of r_{Sch}c. We also investigate the solution for the rotating Bondi flow with the outflow. The outflow affects the determination of the mass accretion rate at the outer boundary. We find that the relation between the mass accretion and the gas angular momentum becomes shallower as the outflow strengthens.We present Herschel Space Observatory far-IR observations of the supernova remnant(SNR) G21.5-0.9. We search PACS-IFU data for 63um [O I], 88um [O III], 157um [C II] emission lines and detect the [O II] and the [C II]. We then produce emission line maps to check the spatial distribution of the elements. We compare the maps to Radio, IR-photometrics, and X-ray images in order to understand interaction of the ejecta with the Pulsar Wind Nebula(PWN) and physical environment in the SNR.We measure X-ray timing and spectral properties of the pulsar PSR J0205+6449. Pulsar's rotation frequency ν = 15.20102357(9) s-1 and its derivative${\dot{\nu}}=-4.5(1){\times}10^{-11}s^{-2}$ are measured, and the pulsed spectrum of 2-30 keV is model of power law with photon index psr = 1.07(16) and F2-30 keV = 7.3(6) × 10-13 erg cm-2 s-1. We use thermal emission models and non-thermal model to fit the pulsar spectrum and measure the surface temperature and luminosity of the pulsar. The surface temperature T∞ = 0.5-0.8 MK and luminosity Lth = 1-5 × 1032 erg s-1 are measure, and this result verifies the previous results known to have low surface temperature and luminosity for the age range of본 연구는 명말(明末)에 역법(歷法)의 개정을 주장한 서광계(徐光啓, 1562~1633)의 기획과 총괄에 의해 편찬되었고, 이탈리아 선교사 로(Giacomo Rho, 羅雅谷, 1593~1638)가 주 저자로 보는 《숭정역서》에서 태양의 이론편인 <일전역지(日躔歷指)>와 계산 절차 및 계산수치표가 종합된 <일전표(日躔表)>의 내용을 정리, 분석하였다. <일전역지>와 <일전표>에 들어있는 몇 개의 내용과 표들은 대부분 16세기 후반부터 17세기 전반에 걸쳐 서유렵의 티코 브라헤(Tycho Brahe, 1546~1601), 마기니(Giovanni Antonio Magini, 1555~1617), 메티우스(Adriaan Metius, 1571~1635) 등의 책에서 동일한 내용이 발견되었다. 판나이 휘집본(潘鼐彙集本; 프랑스 국립도서관본; 《숭정역서》 초기본), 규장각본(《숭정역서》의 후기본), 그리고 사고전서본(《신법산서》)의 내용을 빠짐없이 검토하고, 최근 발간된 《숭정역서합교》의 연구도 반영되었다. <일전역지>에 태양의 운동을 기술하기 위해 Eccentic 모델을 사용하여 양심차(兩心差), 원지점의 방향, 가감차(加減差), 지구-태양간의 거리 변화 등을 설명하고 있다. 그러나 <일전표>에 나타난 가감차표와 지구-태양간의 거리표는 Equant 모델을 사용하였다. 비교를 위하여 70여년 뒤에 편찬된 《역상고성》 상편 제 4권 <일전역리>에서는 코페르니쿠스 모델인 본륜-균륜 모델이 사용되고 있었다. 본 연구에서는 위에 언급된 3 가지 모델의 차이를 설명하고, 가감차와 지구-태양간의 거리표를 이 모델을 이용하여 계산한 다음, <일전표>에 있는 가감차표와 지구-태양간의 거리표와 비교할 것이다. 《신법산서》에는 Equant 모델을 설명하고 있는데 어디서 오류가 발생하였는지도 규명한다. 그리고 3 가지 모델의 animation을 통해 가감차와 거리차를 쉽게 설명하고자 한다.In an attempt to investigate the nonlinear dynamics such as shock, shear, and turbulence associated with ultra-relativistic jets, we develop a new relativistic hydrodynamics (RHD) code based on the weighted essentially non-oscillatory (WENO) scheme. It is a 5th-order accurate, finite-difference scheme, which has been widely used for solving hyperbolic systems of conservation equations. The code is parallelized with MPI and OpenMP. Through an extensive set of tests, the accuracy and efficiency of different WENO reconstructions, and different time discretizations are assessed. Different implementations of the equation of state (EOS) for relativistic fluid are incorporated, As the fiducial setup for simulations of ultra-relativistic jets, we adopt the EOS in Ryu et al. (2006) to treat arbitrary adiabatic index of relativistic fluid, the WENO-Z reconstructions to minimize numerical dissipation without loss of stability, and the strong stability preserving Runge-Kutta (SSPRK) method to achieve stable time stepping with large CFL numbers. In addition, the code includes a high-order flux averaging along the transverse directions for multi-dimensional problems, and the modified eigenvalues for the acoustic modes to effectively control the carbuncle instability. We find that the new code performs satisfactorily simulations of ultra-relativistic jets.Radio relics in the outskirts of galaxy clusters are interpreted as synchrotron radiation due to the relativistic electrons produced via diffusive shock acceleration (DSA) in shocks with low sonic Mach numbers, Ms ≤ 3 in high beta ICM plasma. Electron injection into the DSA process at such weak shocks is one of the key elements, which has yet to be fully understood. In this study, we explore the nature of kinetic microinstabilities excited in weak quasi-perpendicular shocks through 2D particle-in-cell simulations. We find Alfven-ion cyclotron (AIC), whistler, and mirror instabilities can be triggered by ion and electron temperature anisotropy in the immediate downstream of supercritical shocks with Ms > Mcrit ~ 2.3. In particular, AIC instability causes rippling of the shock surface, which in turn generates plasma waves on multi-scales and faciliates the electron preacceleration. Our results may contribute to understanding the origins of radio relics.유구한 전통을 배경으로 우리나라는 유네스코 세계기록유산을 세계 4위, 아시아 1위로 등재하여 기록물의 가치를 국제적으로 인정받고 있다. 이제는 세계 기록유산 16건이라는 등재 수량을 넘어, 활용도 증진을 통한 명실상부 질적 차원의 우수 세계 기록유산 보유국가로 성장해야 할 시기를 맞고 있다. 이러한 측면에서 기록유산의보편적 접근과 활용의 증진을 목적으로 하는 국제기록유산센터(ICDH, International Centre for Documentary Heritage)의 2019년 청주시 유치는 시사하는 바가 크다. 또 정부가 세계 기록유산의 다양한 활용 제고를 위한 지자체 협업 사업을 지원하기 시작한 것도 유의할만하다. 그러나 한국 천문학 분야에서는 세계 기록유산이 한 건도 지정되지 않아 우리나라의 우수한 과학적 성취가 담긴 사료들은 알려지지 않고 있으며, 체계적인 관리·보존도 미비한 상태다. 이에 이 연구는 한국 천문학 기록자원의 세계 기록유산 발굴과 등재 및 등재 이후 활용 증진을 위한 아웃리치 서비스의 방법론을 제언하는 데 목적을 가지며 다음 기획론을 제시하고자 한다. 먼저 한국 천문학 기록자원의 세계 기록유산 발굴을 위하여 유네스코의 등재평가기준과 참고할만한 등재과정의 선행사례를 분석한다. 다음으로, 등재 이후 정·관·학 협업의 체계적 관리보존과 공유체계를수립하는 방안을 모색하고자 한다. 이를 위하여 소장처와협업체간 분쟁의 소지가 될 수 있는 저작권 등 위험 요소와 참고할만한 국내외 협업의 선진사례를 분석한다. 마지막으로 한국 천문학계의 요구와 현실에 부합하는 기록학적방법론을 분석하여 한국 천문학 분야 세계 기록유산의 아웃리치서비스 방안을 제언하고자 한다. 이 연구는 천문학 분야에서 망실·훼손될 수 있는 기록 자원을 발굴하는 계기를 세계 기록유산에서 찾아, 천문학계에 새로운 연구의 장(場)을 창출하는 선순환을 도모했다는 점에서 의의가 있다. 그러나 선험적 기획이므로 과정상 발생할 수 있는 변수의 대처 방안과 유의성 분석 등 연구 결과 검증에는 한계가 있다. 향후 한국 천문학과의 협업으로 세계 기록유산과 관련한 사료 발굴과 가치 고증 등 학술적 이론 검증을 이어나가 다양한 학제 간 연구로 심화하길 기대한다.Seo, Yoon Kyung;Kim, Sang Hyuk;Ahn, Young Sook;Choi, Go-Eun;Choi, Young Sil;Baik, Hangi;Sun, Bo Min;Kim, Hyun Jin;Choi, Byung Sook;Lee, Sahng Woon;Park, Raejin 56.1
한국의 고문헌 중에는 다양한 고천문 기록들이 한문 형태로 존재하며, 이를 학술적으로 활용하기 위해서는 전문 번역가 투입에 따른 많은 비용과 시간이 요구된다. 이에 인공신경망 기계학습에 의한 인공지능 번역기를 개발하여 비록 초벌 번역 수준일지라도 문장 형태의 한문을 한글로 자동번역해 주는 학술 도구를 소개하고자 한다. 이 자동번역기는 한국천문연구원이 한국정보화진흥원이 주관하는 2019년도 Information and Communication Technology 기반 공공서비스 촉진사업에 한국고전번역원과 공동 참여하여 개발 완료한 것이다. 이 연구는 고천문 도메인에 특화된 인공지능 기계학습용 데이터인 천문 고전 코퍼스를 구축하여 이를 기반으로 천문 고전 특화 자동번역 모델을 개발하고 번역 서비스하는 것을 목적으로 한다. 이를 위해 구축되는 시스템은 크게 세 가지이다. 첫째, 로그인이 필요 없이 누구나 웹 접속을 통해 사용이 가능한 클라우드 기반의 고문헌 자동번역 대국민서비스 시스템이다. 둘째, 참여 기관별로 구축된 코퍼스와 도메인 특화된 번역 모델의 생성 및 관리할 수 있는 클라우드 기반의 대기관 서비스 플랫폼 구축이다. 셋째, 개발된 자동번역 Applied Programmable Interface를 활용한 한국천문연구원 내 자체 서비스가 가능한 AITHA 시스템이다. 연구 결과로서 먼저 구축된 천문 고전 코퍼스 60,760건에 대한 샘플링 검수 결과는 품질 순도 99.9% 이상이다. 아울러 도출된 천문 고전 특화 번역 모델 총 20개 중 대표 모델에 대한 성능 평가 결과는 기계 번역 텍스트 품질 평가 알고리즘인 Bilingual Evaluation Understudy 평가에서 40.02점이며, 전문가에 의한 휴먼 평가에서 5.0 만점 중 4.05점이다. 이는 당초 연구 목표로 삼았던 초벌 번역 수준에 충분하며, 현재 개발된 시스템들은 자체 시험 운영 중이다. 이 연구는 특수 고문헌에 해당되는 고천문 기록들의 번역 장벽을 낮춰 관련 연구자들의 학술적 접근 및 다양한 연구에 도움을 줄 수 있다는 점에서 의의가 있다. 또한 고천문 분야가 인공지능 자동번역 확산 플랫폼 시범의 첫 케이스로써 추후 타 학문 분야 참여 시 시너지 효과도 기대해 볼 수 있다. 고문헌 자동번역기는 점차 더 많은 학습 데이터와 학습량이 쌓일수록 더 좋은 학술 도구로 진화할 것이다.2019년 10월, 젊은 천문학자 모임(Young Astronomers Meeting, 이하 YAM)은 가을 정기총회를 가졌으며, 2020년 임원진으로 회장 서울대학교 이가인, 부회장 서울대학교 백인수 회원이 선출되었다. 운영위원으로는 서울대학교 강지수, 경북대학교 김이곤, 경희대학교 이용희, UST 임효빈, 충남대학교 정미지, 세종대학교 최보은, 연세대학교 최우락 회원이 임명되었다. 매년 진행되어 오던 YAM 워크샵이 지난 2월 27일에 1박 2일동안 한국천문연구원에서 개최될 예정이었으나, 코로나19 사태로 인해 무기한 연기되었고 이밖의 많은 활동들에도 제약이 따랐다. 현재 YAM은 본 모임의 온라인 소식지인 <하늘사랑> 제 9호 발간 및 온라인 모임을 준비함으로써 직접 만나기 어려운 회원들의 소식을 공유하고자 한다. 본 포스터에서는 2020년 상반기 활동을 보고하고 하반기 활동 계획에 대해 논의하고자 한다.The pandemic of COVID-19 has made it difficult to gather participants in offline astronomical programs since March, 2020. For this reason Gwacheon National Science Museum has developed online programs of the partial solar eclipse and the Asteroid Day event in June, the celebration for launching Mars 2020 in July and Perseids in August. In this poster, we present how to plan each of them and research on methods that deliver astronomical contents to viewers effectively. In addition, we introduce preparing a couple of online programs in the rest of this year.Aso, Yusuke;Kwon, Woojin;Ching, Tao-Chung;Lai, Shih-Ping;Li, Zhi-Yun;Hirano, Naomi;Rao, Ramprasad 57.2
We observed the Class I protostar TMC-1A in polarized dust emission at 1.3 mm at a spatial resolution of ~40 au using ALMA. Previous observations revealed a disk (r~100 au), surrounded by an infalling envelope, and a CO outflow going in the north-south direction in TMC-1A. Our observations detected polarized dust emission in a central region (r~50 au) and ~100 au north and south of the central protostar. The former polarization is likely due to self-scattering because of the polarization direction along the disk minor axis, the polarization fraction independent of Stokes I, and a high optical thickness. The latter polarization is roughly in the outflow region. The position and direction, particularly in the north, imply multiple possible mechanisms: magnetically or mechanically aligned dust grains in the outflow or in an accretion flow.The chemical and kinematic properties of stars in the Galactic halo provide crucial information on the origin of the Galactic halo as well as the assembly history of the Milky Way. In this study, we present metallicity distribution functions (MDFs) in different regions of the Galactic halo as well as the kinematic characteristics in each region. The different MDFs and kinematic properties of stars in investigated regions allow us to associate them with the possible progenitor dwarf galaxies discovered to date; hence the assembly history of the Galactic halo.The B-fields in Star-forming Region Observations (BISTRO) is a large program of the James Clerk Maxwell Telescope (JCMT) to study the roles of magnetic fields in molecular clouds on intermediate scales (a few thousands au or larger scales), in which a large number of researchers over the world are involved. This project was initiated in 2016 with polarimetric observations of nearby star-forming regions and has been extended toward massive and farther regions (BISTRO-2) and various evolutionary stages and environmental conditions (BISTRO-3). The current status of the BISTRO projects is reported. In addition, we discuss magnetic fields in the Serpens Main molecular cloud, which is one of the BISTRO star-forming regions. Utilizing the Histogram of Relative Orientations method, which compares polarization directions with density gradients, we show that magnetic fields are parallel to filaments in less dense filamentary structures but perpendicular to dense ones. Furthermore, the magnetic field directions with respect to density gradients vary again with density in denser core regions, which is understood by core formation and pinched fields. Note: (PI) D. Ward-Thompson, (co-PIs) P. Bastien, T. Hasegawa, W. Kwon, S. Lai, and K. QiuThe Multipupose InfraRed Imaging System (MIRIS) Paα Galactic Plane Survey (MIPAPS) covers the whole Galactic plane with the latitude range of -3° < b < +3°. Next to the first result in l = 96°-116° (Cepheus), we present the results in l = 276°-296° (Carina). This region with the direction toward the inner Galaxy, has much higher extinction but much more Paα-emitting sources than Cepheus. We list up the detected Paα sources, and compare them with the WISE H II region catalog (there are 308 H II regions and candidates in this region) and VPHAS+ Hα image. By detecting the Paα and Hα recombination lines, 71 H II region candidates are newly confirmed as definite H II regions, out of which 53 H II regions are detected at Paα. For the Paα-detected sources, we measure the Paα and Hα fluxes and estimate the E(B-V) color excesses for the extended sources.We present a method for determining the abundance ratio of nitrogen to iron ([N/Fe]) from low-resolution (R~2000) stellar spectra from large spectroscopic surveys such as Sloan Digital Sky Survey (SDSS) and Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). The basic idea of the method is to match a grid of synthetic spectra with an observed spectrum in the CN band region around 3883 Å. To calibrate our estimate of [N/Fe], we make use of the giants observed in Apache Point Observatory Galaxy Evolution Experiment (APOGEE), which are also observed in the SDSS. This method will be applied to the Galactic halo stars to determine [N/Fe], and the measured nitrogen abundance ratios will be used to investigate the C-N anti-correlation, which is observed in globular clusters, to trace their origin with their kinematic properties.We present spatial variations of chemical abundances ([Fe/H] and [α/Fe]) in the Galactic disk, using a large number of dwarfs and giants from Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST). Specifically, we investigate how the metallicity distribution function (MDF) and the alpha abundance distribution function (ADF) change with the distance from the Galactic center to understand the chemical evolution history of the Galactic disk. We also study the difference (if any) in the MDF and ADF between dwarfs and giants to provide valuable clues to the formation history of the Galactic disk.We present preliminary results of 1.1 and 1.3 mm dust continuum and 12CO (J=2-1) line data obtained with the Submillimeter Array toward six cores harboring Class 0/I objects in the λ Orionis cloud. They are located in bright rimmed clouds, which are exposed to the far-ultraviolet radiation field by the O-type star λ Ori. Compact dust continuum emission is observed from all six cores. Among the six cores, only one core G196.92-10.37 shows a signature of binarity with separation of 4000 AU. The numbers of singles and binaries in our sample are five and one, respectively and the derived multiplicity frequency (MF) is 0.17. This value is lower than those found in the binary surveys toward Class 0/I objects, which may be a hint for negative feedback by the nearby massive star, lambda Ori. The derived excitation temperature (Tex) using 12CO emission shows a lower median value (20 K) than those of triggered star-forming regions (30 K). The lower MF and Tex support our previous study that star formation was not triggered in the λ Orionis cloud. We aim to further investigate whether the Class 0/I YSOs in the λ Orionis cloud have less circumstellar materials and smaller accretion rates than in other filamentary clouds (e.g., Orion A & B), which might be attributed to negative feedback from the massive star in limiting accretion of protostars.Extremely metal-poor (EMP; [Fe/H] < -3.0) stars are thought to be genuine second-generation of stars because they were born from relatively pristine gas chemically enriched by one or two supernovae. So, the EMP stars presumably originated from outside the Milky Way (MW) are important tracers for the early chemical evolution and assembly history of the MW. In this study, we present the preliminary results on the early assembly history of the MW inferred by associating the dynamical properties of our EMP stars with those of known substructures in the MW. We also explore the star formation history of the progenitor galaxies of our EMP stars by investigating the elemental abundances of the EMP stars associated with the substructure.Disks around protostars are the birthplace of planets. The first step toward planet formation is grain growth from ㎛-sized grains to mm/cm-sized grains in a disk, particularly in dense regions. In order to study whether grains grow and segregate at the protostellar stage, we investigate the ALMA Band 3 (3.1 mm) and 7 (0.87 mm) dust continuum observations of the protostellar disk WL 17 in ρ Ophiuchus L1688 cloud. As reported in a previous study, the Band 3 image shows substructures: a narrow ring and a large central hole. On the other hand, the Band 7 image shows different substructures: a non-axisymmetric ring and an off-center hole. The two-band observations provide a mean spectral index of 2.3, which suggests the presence of mm/cm-sized large grains. Its non-axisymmetric distribution may imply dust segregation between small and large grains. We perform radiative transfer modeling to examine the size and spatial distributions of dust grains in the WL 17 disk. The best-fit model suggests that large grains (>1 cm) exist in the disk, settling down toward the midplane, whereas small grains (~10 ㎛) well mixed with gas are distributed off-center and non-axisymmetrically in a thick layer. The low spectral index and the modeling results suggest that grains rapidly grow at the protostellar stage and that grains differently distribute depending on sizes, resulting in substructures varying with observed wavelengths. To understand the differential grain distributions and substructures, we discuss the effects of the protoplanet(s) expected inside the large hole and the possibility of gravitational instability.We present the results of polarization observations at submillimeter wavelengths towards Monoceros R2 (Mon R2). The polarized thermal dust emission was obtained from SCUBA-2/POL-2 at 450 ㎛ and 850 ㎛, simultaneously. This observation is a part of the JCMT BISTRO survey project. The polarization angle distributions at 450 ㎛ and 850 ㎛ are similar and the mean value of angle differences at two wavelengths is 5.5 degrees. The Mon R2 is one of massive star-forming regions containing a clear hub-filamentary structure. The hub region shows star formation activities, and surrounding filaments provide channels for matters to move into the hub region. It is not well known the role of magnetic fields in a hub-filamentary structure. Some studies have shown well-ordered polarization segments along a filamentary structure and magnetic field morphology traced by polarization segments is interpreted as to help gas flow along the filamentary structrue. Our observations shows that filaments in Mon R2 have spiral structure and the magnetic field lines are parallel to the filaments. We interpret that the spiral structure can be formed by a rotation hub-filament system with gas flowing along the filaments to the hub. We found several dust clumps at the central part of the hub region of the Mon R2. They seems to be formed at locations where spiral field lines meet each other. These results show one observational example that a magnetic field play a role in gas flow.We present optical variability of nearby luminous active galactic nucleus (AGN). We use the multi-epoch data of 46 AGNs obtained from 2015 to 2019 through SNU AGN Monitoring Project (SAMP), which was carried out for the reverberation mapping of luminous AGNs. We estimated variability amplitudes and time scales using the various types of analytic function, such as structure function and damped random work. We present the comparisons between physical properties of AGNs and optical variability in order to unveil the origin of the variability of AGNs.Kim, Sanghyun;Kim, Minjin;Byun, Woowon;Sheen, Yun-Kyeong;Ho, Luis C;Lee, Joon Hyeop;Kim, Sang Chul;Jeong, Hyunjin;Park, Byeong-Gon;Seon, Kwang-Il 60.2
In the hierarchical framework, galaxies grow through mergers and accretion. Those mechanisms leave faint features, such as stellar streams, shells and smooth stellar halos in the outskirts of galaxies. In order to search for those features in the nearby galaxies, we are conducting a KMTNet Nearby Galaxy Survey using the Korea Microlensing Telescope Network. We present a deep and wide-field imaging of NGC 5236, a barred spiral galaxy. In one-dimensional surface brightness profiles, we reach 28, 29 mag/arcsec2 in the R- and B-band, respectively. We find that the outer disk of NGC 5236 can be well described with a single exponential profile up to 17 kpc (~3.8 Reff) indicating that the excess light due to the stellar halo is not clearly detected. B-R color gradually increases towards the outskirts of the galaxy. It may reveal that stellar properties in the outskirts are marginally distinctive from those in the central part.We perform disk-halo decomposition of the Large Magellanic Cloud (LMC) using a novel HI velocity field extraction method, aimed at better deriving its HI kinematics and thus the dark matter density profile. For this, we use two newly developed galaxy kinematic analysis tools, BAYGAUD and 2DBAT which have been used for the kinematic analysis of resolved galaxies from Australian Square Kilometre Array (ASKAP) observations like WALLABY which is an all-sky HI galaxy survey in southern sky. By applying BAYGAUD to the combined HI data cube of the LMC taken with the Australia Telescope Compact Array (ATCA) and Parkes radio telescopes, we decompose all the line-of-sight velocity profiles into an optimal number of Gaussian components based on Bayesian MCMC techniques. From this, we disentangle turbulent non-circular gas motions from the overall rotation of the galaxy. We then derive the rotation curve of the LMC by applying 2DBAT to the separated circular motions. The rotation curve reflecting the total kinematics of the LMC, dark and baryonic matters is then be combined with the mass models of baryons, mainly stellar and gaseous components in order to examine the dark matter distribution. Here, we present the analysis of the extracted HI gas maps, rotation curve, and J, H and K-band surface photometry of the LMC.We examine the HI gas kinematics and distribution of galaxy pairs in group or cluster environment from high-resolution Australian Square Kilometre Array Pathfinder (ASKAP) WALLABY pilot observations. We use 22 well-resolved galaxies in the Hydra cluster of which 4 galaxies are visually identified as pairs and others are isolated ones. We perform profile decomposition of HI velocity profiles of the galaxies using a new tool, BAYGAUD which enables us to separate a line-of-sight velocity profile into an optimal number of Gaussian components based on Bayesian MCMC techniques. All the HI velocity profiles of the galaxies are decomposed into kinematically cold or warm gas components with their velocity dispersion, 4~8 km/s or > 8 km/s, respectively. We derive the mass fraction of the kinematically cold gas with respect to the total HI gas mass, f = log10(M_cold / M_HI), of the galaxies and correlate them with their dynamical mass. The cold gas reservoir of the paired galaxies in the Hydra cluster is found to be relatively higher than that of the isolated ones which show a negative correlation with the dynamical mass in general.We study the overdensity of near-infrared sources around 508 sub-mm sources classified as dusty galaxies in the SPT-SZ survey catalog observed in 95 GHz (3.15 mm), 150 GHz (2 mm) and 250 GHz (1.2 mm) bands. We used the VISTA hemisphere survey data release 6 (VHS DR6) catalog covering the J, H, Ks bands. The mean number of galaxies within a radius of 60 arcsec (corresponding to about 500 kpc at z=2) from 500 randomly selected positions is 14.4, while the galaxy number distribution is approximated as a Gaussian with a standard deviation of 7.9. From the 2500 deg2 of SPT-SZ survey + VHS DR6 data, there were 27 sub-mm sources that have galaxy overdensity higher than 4σ. We present color-magnitude diagram around 27 selected sub-mm sources with enhanced galaxy surface densities, in order to investigate the presence of structure around sub-mm sources.We present spatially resolved outflows and photoionization for a pilot sample of 11 type 1 AGNs (z<0.3) based on the Gemini Multi-Object Spectrograph Integral Field Unit data. These AGNs were selected since we found strong outflow signatures in SDSS spectra. We focus on [OIII] and Hα emission lines to probe outflow kinematics by measuring line flux, velocity, and velocity dispersion at each pixel. We investigate characteristics of gas kinematics of type 1 AGNs and compare them with those of type 2 AGNs in our previous studies. Furthermore, by drawing BPT map, photoionization states will be also discussed. Based on the results, we discuss various implications on the impacts of outflows on star formation in host galaxies.We present H I gas kinematics and star formation activities of NGC 6822, a dwarf galaxy located in the Local Volume at a distance of ~490 kpc. We perform profile decomposition of the line-of-sight velocity profiles of the high-resolution (~42.4" × 12") spatial; ~1.6 km/s spectral) H I data cube taken with the Australia Telescope Compact Array (ATCA). For this, we use a new tool, the so-called BAYGAUD (BAYesian GAUssian Decompositor) which is based on Bayesian Markov Chain Monte Carlo (MCMC) techniques, allowing us to decompose a line-of-sight velocity profile into an optimal number of Gaussian components in a quantitative manner. We classify the decomposed H I gas components of NGC 6822 into kinematically cold, warm or hot ones with respect to their velocity dispersion: 1) cold: < 4 km/s, 2) warm: 4 ~ 8 km/s, 3) hot: > 8 km/s. We then derive the Toomre-Q parameters of NGC 6822 using the kinematically decomposed H I gas maps. We also correlate their gas surface densities with the surface star formation rates derived using both GALEX far-ultraviolet and WISE 22 micron data to examine the impact of gas turbulence caused by stellar feedback on the Kennicutt-Schmidt (K-S) law. The kinematically cold component is likely to better follow the linear extension of the Kennicutt-Schmidt (K-S) law for molecular hydrogen (H2) at the low gas surface density regime where H I is not saturated.We present a scaling relation between black hole (BH) mass and bulge luminosity for 35 nearby (z<0.1) type 1 active galaxies, selected from the 70-month Swift-BAT X-ray source catalog. Thanks to the unbiased selection and proximity of the parent sample, our sample is suitable to study the physical connection between central black holes and host galaxies. We use the F814W images obtained with the Advanced Camera for Surveys on Hubble Space Telescope, to perform the imaging decomposition with GALFIT. With a careful treatment on the PSF model, we measure the I-band bulge brightness robustly. In combination with the BH mass estimated from a single-epoch spectroscopic data, we present the correlation between BH mass and bulge luminosity of the target AGNs. We demonstrate that our sample marginally lies off from the M(BH)-L(bulge) relation of inactive galaxies. We discuss possible physical origins of this discrepancy. Finally, we present how the relation depends on the photometric properties of AGNs and host galaxies, which may provide an useful insight on the co-evolution between BHs and host galaxies.Globular clusters(GCs) are found not only around galaxies (galaxy GCs), but also between galaxies in galaxy clusters (intracluster GCs; ICGCs). The ICGCs, which are not bound to any of cluster member galaxies, are governed by the galaxy clutster potential. ICGCs have been detected in the wide field of Virgo and Fornax galaxy clusters. However, previous surveys covered only a small fraction of Coma and Perseus. In this study we present a wide field survey of these two galaxy clusters, using Subaru Hyper Suprime-Cam(HSC) archival images, covering a circular field with diameter of ~1.8 deg. We select ICGC candidates, by masking the images of bright galaxies and choosing point sources in the remaining area. We find thousands of ICGCs in each galaxy cluster. These ICGCs show a bimodal color distribution, which is dominated by blue GCs. We investigate spatial distributions and radial number density profiles of the blue and red ICGCs in each galaxy cluster. Implications of the results will be discussed.We investigate the effect of recent star formation (RSF) on the α-elements-to-iron ratio ([α/Fe]) estimation for galaxies. Measuring galactic [α/Fe] is a powerful tool to pinpointing the timescale of chemical evolution and star formation. Our working hypothesis is that, with increasing stellar surface temperature, absorption equivalent width (EW) of α-elements decreases faster than that of Fe-peak elements, and thus RSF will lower the line ratio of EW(α)/EW(Fe). Moreover, young stars outshine, effectively lowering EW(α)/EW(Fe) of integrated light of RSF galaxies. Here we test our hypothesis using SDSS (optical spectrophotometric), GALEX (UV photometric) and IllustrisTNG datasets, and show that, if RSF is not considered thoroughly, EW(α)/EW(Fe) lowered by RSF can be routinely misinterpreted as low [α/Fe]. We discuss possible implications of the result in the context of the conventional [α/Fe]-mass relation of galaxies.FLASH: The First Large Absorption Survey in HI with the Australian Square Kilometre Array PathfinderFLASH is a blind neutral hydrogen (HI) absorption line survey, eventually targeting about 100,000 background radio continuum sources in the entire southern sky using the full 36-antenna of the Australian Square Kilometre Array Pathfinder (ASKAP). Our primary goal is to search for associated and intervening HI absorption lines in the intermediate redshift range 0.4 < z < 1.0. The survey aims to understand the evolution of HI gas in galaxies as well as various physical mechanisms in active galactic nuclei, such as accretion and feedback processes. In this poster, we give an overview of the FLASH survey and present the preliminary results from our first 100-hrs of pilot observations. The latest survey data covers 1,000 square degrees and is ideal for validating observation and data processing in the continuous 300MHz-width low frequency ASKAP band (700-1000MHz). One of the crucial objectives of the pilot survey is to establish the analysis methodology that will be applied to upcoming large absorption surveys in the future. We discuss our data quality validation and present some detections of associated/intervening HI absorption lines. These absorption lines allow us to trace the cold gas properties of active and normal galaxies at higher redshifts where the HI emission line is too weak to be detectable.수소 라이먼 알파선은 관측이 어려운 외부은하의 성간 물질이나 성운 주위의 물질의 운동학적, 기하학적 상태를 알려주는 지표이다. 특히 라이먼 알파 방출 스펙트럼의 두 최고점에서 측정한 선속도 차이는 물질의 수축, 팽창 여부에 영향을 받기 때문에 은하의 역학적 특성을 연구하는 데에 있어 새로운 도구로서 각광받고 있다. 관측에서 얻어지는 은하들의 선속도 차이는 100km/s에서 800km/s까지 넓은 영역에서 존재한다. 선행 분자구름 규모의 연구에서 얻어진 선속도 차이는 상대적으로 작은 선속도 차이(148.54km/s)를 가진다. 그래서 이 연구에서는 더 큰 규모인 은하에서 라이먼 알파 선속도 차이를 확인하고 은하내 물리량의 영향을 알아보았다. 이 연구에서는 복사유체역학 시뮬레이션 코드 RAMSES-RT를 활용한, 각각 다른 물리량을 가진 은하 시뮬레이션 결과를 활용하였다. 은하 내 가스의 비율, 금속함량비를 다르게 하였으며, 각 시뮬레이션들은 몬테- 카를로 공진선 복사전달 코드 RASCAS를 이용하여 라이먼 알파선의 복사 과정을 계산하였다. 첫 번째로 기준 은하 시뮬레이션과 분자구름 시뮬레이션(Kimm+19)의 결과를 비교한 결과 148.54km/s에서 221.76km/s로 선속도 차이의 평균 값이 상승한 것을 확인하였다. 이는 성간 물질의 존재 유무의 차이로 인한 것이다. 은하 내 가스의 금속함량비를 증가시킨 경우, 은하 내 먼지량과 젊은 별들이 별 생성 구름에 머무는 시간이 증가하기 때문에 기준 은하와 비교하여 선속도 차이가 작아졌다.(206.9km/s) 반면 은하의 가스량을 증가시켯을 때는 산란 횟수 증가로 인한 상대적으로 큰 선속도 차이(298.51km/s)를 확인할 수 있었다. 또한 기준은하에 대해, 난류의 효과를 포함하여 선속도 차이를 비교한 결과, 선속도 차이는 (308.8km/s)상승하였다. 이를 통해 성간 물질의 물리량 차이만으로는 400km/s 이상의 큰 선속도 차이를 만드는 것은 어렵다. 관측에서 보이는 400km/s 이상의 몇몇 큰 선속도 차이의 은하를 위해서는 이 시뮬레이션에 포함되지 않은 성운 주위의 물질과 같은 부분이나, 은하 합병과 같은 극한의 상황이 필요할 것이다.Lee, Bumhyun;Wang, Jing;Chung, Aeree;Ho, Luis C.;Wang, Ran;Shao, Li;Michiyama, Tomonari;Wang, Shun;Peng, Eric W.;Kilborn, Virginia 64.1
Galaxy groups are the place where many galaxies feel the impact of the surroundings (e.g., merging, tidal interaction, ram pressure stripping) before joining bigger structures like (sub)clusters. A significant fraction of galaxies is quenched in the group environment. Such "pre-processing" of galaxies in groups is likely to affect galaxy evolution tremendously. To better understand how environmental processes in galaxy groups affect molecular gas, star formation activity, and galaxy evolution, we carried out CO imaging observations of group galaxies, using the Atacama Compact Array (ALMA/ACA). We selected all the targets that have been detected in the GEMS-HI survey for two groups, making the sample of 40 galaxies (18 galaxies in IC 1459 group and 22 galaxies in NGC 4636 group). Our ALMA/ACA observation is the first CO imaging survey for two groups. In this work, we present CO images of group galaxies, together with their star formation maps and HI images. Our ACA CO data show the asymmetric distribution of molecular gas in some of our samples. We discuss the impact of the group environment on molecular gas and star formation activity.We present the properties of galaxies in filaments around the Virgo cluster with respect to their vertical distance from the filament spine. Using the NASA-Sloan Atlas and group catalogs, we select galaxies that do not belong to groups in filaments. The filament member galaxies are then defined as those located within 3.5 scale length from the filament spine. The filaments are mainly (~86%) composed of low-mass dwarf galaxies of logh2M∗/M⊙ < 9 dominantly located on the blue cloud in color-magnitude diagrams. We observe that the g - r color and stellar mass of galaxies correlate with their vertical distance from the filament spine in which the color becomes red and stellar mass decreases with increasing vertical filament distance. The galaxies were divided into two subsamples in different stellar mass ranges, with lower-mass (logh2M∗/M⊙ ≤ 8) galaxies showing a clear negative g-r color gradient, whereas higher-mass (logh2M∗/M⊙ > 8) galaxies have a flat distribution against the vertical filament distance. We observe a negative EW(Hα) gradient for higher-mass galaxies, whereas lower-mass galaxies show no distinct variation in EW(Hα) against the vertical filament distance. In contrast, the NUV - r color distribution of higher-mass galaxies shows no strong dependence on the vertical filament distance, whereas the lower-mass galaxies show a distinct negative NUV - r color gradient. We do not witness clear gradients of HI fraction in either the higher- or lower-mass subsamples. We propose that the negative color and stellar mass gradients of galaxies can be explained by mass assembly from past galaxy mergers at different vertical filament distances. In addition, galaxy interactions might be responsible for the contrasting features of EW(Hα) and NUV - r color distributions between the higher- and lower-mass subsamples. The HI fraction distributions of the two subsamples suggest that ram-pressure stripping and gas accretion could be ignorable processes in the Virgo filaments.It has been studied that galaxies evolve following a typical trajectory on the phase space under the influence of deep gravitational potential of galaxy clusters. Similarly, the large-scale filaments could also affect the evolution of galaxies before falling into the clusters. In this study, using a dark matter-only cosmological simulation, N-Cluster Run, we explore the evolution of galaxies on the phase space drien by large-scale filaments. We find that galaxies around the filaments form a common trajectory on the phase space as well as cluster galaxies do. We also examine how these trajectories change depending on various physical parameters such as galaxy mass, initial distance of galaxies from large-scale filaments, and cluster mass.We present high-resolution, high-sensitivity continuum data of NGC 4522 observed at 3 cm (X-band) and 10 cm (S-band) in full polarization mode using the JVLA. This observation has 2 - 4 times better spatial resolution and 2 - 5 times better sensitivity compared to previous continuum observations. NGC 4522 is a Virgo spiral galaxy undergoing active ram pressure stripping. This galaxy is particularly well known for the CO emission detected outside its stellar disk, some of which coincides with the extraplanar HI gas and Halpha patches. The major goal of our JVLA observation is to leverage our understanding of the influence of the ram pressure on the general ISM field and multi-phase medium. By combining our new deep radio continuum data and previous observations, we will investigate how the B-field properties can be affected by the ram pressure, and what roles the B-field plays in the stripping process of the multi-phased ISM and in the star formation activity when the ram pressure is present.We present NIR spectroscopic data of young radio quasars obtained from Flamingos-2 (F2) at Gemini-South. The targets are originally selected from Wide-Field Infrared Survey Explorer survey in combination with radio survey data, such as FIRST and NVSS. Our goal is to find observational evidence of jet-driven outflows, which is expected to be present in young luminous quasars from the theoretical studies. While 16 targets were observed with F2, narrow emission lines ([O III] or Hα) were detected in 7 targets. FWHM of the emission lines (up to 2500 km/s) were remarkably broad compared to ordinary quasars, revealing the presence of strong outflows. The black hole mass estimated from Eddington limit ranges from ~108 to 109 solar mass, indicating that the target quasars are likely to be progenitors of massive galaxies. Finally, we present the comparisons between the outflow velocity and the physical properties of radio jets derived from the VLA radio imaging data, in order to investigate the physical connection between the ionized outflows and radio jets.We use the IllustrisTNG cosmological hydrodynamical simulation to study the evolution of star formation rate (SFR)-density relation over cosmic time. We construct several samples of galaxies at different redshifts from z=2.0 to z=0.0, which have the same comoving number density. The SFR of galaxies decreases with local density at z=0.0, but its dependence on local density becomes weaker with redshift. At z≳1.0, the SFR of galaxies increases with local density (reversal of the SFR-density relation), and its dependence becomes stronger with redshift. This change of SFR-density relation with redshift still remains even when fixing the stellar masses of galaxies. The dependence of SFR on the distance to a galaxy cluster also shows a change with redshift in a way similar to the case based on local density, but the reversal happens at a higher redshift, z~1.5, in clusters. On the other hand, the molecular gas fraction always decreases with local density regardless of redshift at z=0.0-2.0 even though the dependence becomes weaker when we fix the stellar mass. Our study demonstrates that the observed reversal of the SFR-density relation at z≳1.0 can be successfully reproduced in cosmological simulations. Our results are consistent with the idea that massive, star-forming galaxies are strongly clustered at high redshifts, forming larger structures. These galaxies then consume their gas faster than those in low-density regions through frequent interactions with other galaxies, ending up being quiescent in the local universe.Development of public release system of science mission data from KPLO and future space explorations우리나라는 최초의 우주탐사선이자 달탐사선인 KPLO를 2022년 8월에 발사할 예정이다. KPLO에는 6기의 임무탑재체가 실리게 되며, 이중 4개의 탑재체는 국내의 대학과 정부출연연구소에서 개발하여 달 표면과 주변 우주환경에 대한 과학임무를 수행하게 된다. 이들 국내에서 개발된 과학탑재체가 달 궤도에서 획득한 Data, 즉 과학자료는 지상국에서 수신하여 이를 처리하여 과학연구 혹은 교육 목적으로 활용될 것으로 예상된다. 이러한 태양계 탐사 과학임무로 부터 획득된 과학자료는 과학의 공익성과 연구교류 활성화를 위해서 국제적으로 대중에게 공개하고 있다. 이에 KPDS도 일반 사용자들이 인터넷으로 이들 과학자료를 쉽게 검색하고 다운로드 받을 수 있도록 한국항공우주연구원에서는 KARI Planetary Data System(KPDS)를 구축하고 있으며, 일반에게 공개할 예정이다. KPDS는 단순히 과학자료를 제공하는 것에서 그치지 않고, 이들 과학자료가 NASA에서 개발한 PDS4 표준을 준수하고 있는지 검증함으로써 세계 각국의 타 우주관련 기관과 상호활용이 용이하도록 하여 활용성을 높은 과학자료로 관리하게 된다. 또한 이러한 PDS4 표준 준수여부를 검증함으로써 KPLO 이후 우리나라에서 수행하게 될 미래의 우주탐사 과학임무로부터 획득될 과학자료도 저장, 공개를 할 수 있도록 KPDS는 범용성을 고려하여 개발하고 있다.Deep Learning Study of the 21cm Differential Brightness Temperature During the Epoch of ReionizationWe propose a deep learning analysis technique with a convolutional neural network (CNN) to predict the evolutionary track of the Epoch of Reionization (EoR) from the 21-cm differential brightness temperature tomography images. We use 21cmFAST, a fast semi-numerical cosmological 21-cm signal simulator, to produce mock 21-cm maps between z = 6 ~ 13. We then apply two observational effects, such as instrumental noise and limit of (spatial and depth) resolution somewhat suitable for realistic choices of the Square Kilometre Array (SKA), into the 21-cm maps. We design our deep learning model with CNN to predict the sliced-averaged neutral hydrogen fraction from the given 21-cm map. The estimated neutral fraction from our CNN model has great agreement with the true value even after coarsely smoothing with broad beam size and frequency bandwidth and heavily covered by noise with narrow beam size and frequency bandwidth. Our results show that the deep learning analyzing method has the potential to reconstruct the EoR history efficiently from the 21-cm tomography surveys in future.Park, Woojin;Chang, Seunghyuk;Pak, Soojong;Han, Jimin;Ahn, Hojae;Lee, Sunwoo;Kim, Geon Hee;Lee, Dae-Hee 66.3
We present the optical design of Linear Astigmatism Free - Three Mirror System (LAF-TMS) D200 for UVO-Multiband Polarizing Imager System (UVOMPIS). LAF-TMS D200 is the off-axis wide-field telescope with EPD = 200 mm, F/2, and Field of View (FoV) = 2° × 4°. Its optical mirrors are optimized to freeform surfaces for high-quality optical performance over a wide FoV. The proposed mirror holder consists of four aluminum optomechanical modules that have applied for LAF-TMS D150 which is a prototype of the LAF-TMS system. It can accurately mount mirrors and also can sustain from vibration environments. As a feasibility study, quasi-static, modal, harmonic, and random vibration analyses have been performed to LAF-TMS D150 optomechanical structure under the qualification level of the Soyuz-2/Fregat launch system. We evaluate the vibration analysis results in terms of von Mises stress and Margin of Safety.Gyeonggi science high school for the gifted (GSHS) installed 60cm telescope, which is waiting for student observers. It is essential to understand the characteristics of the photometric system, consisting of telescope, filter, and CCD, to get reliable data. CCD images of SA98 Landolt standard field and M67 were obtained on 19th March 2020. The images of each field were combined by filters, i.e., we ignored the monochromatic atmospheric extinction since the photometric objects themselves are standard stars. 24 standard stars in SA98 field and 12 standard stars in M67 were used to derive the tentative transformation equation between our bv photometric system and Johnson BV photometric system. In this poster, we present the preliminary standardization result for Johnson BV photometric system in GSHS 60cm telescope. The reproductivity is discussed by comparing color coefficients of two fields. We plan to extend this process to Johnsons-Cousins BVRI photometric system and narrow-band filters for flux calibration.Adaptive Optics (AO) is the technology for ground-based telescopes to overcome the interference caused by atmospheric turbulence. We are developing an AO system for the 1-m telescope at Seoul National University Observatory (SNUO). The seeing size of the SNUO is 2 arcseconds on average, and 0.85 arcseconds at best condition. Our system is based on MEMS deformable mirror and Shack-Hartmann wavefront sensor. We developed the wavefront sensor using a cheap CMOS camera, and measured phase disturbance at SNUO. To verify the performance of the AO system, we designed an artificial phase disturber that produces similar scale phase error, measured at SNUO. We carried out laboratory tests in which the AO system measures and corrects the wavefront using the phase disturber and an F/6 light source, the same as that of SNUO telescope. The control system was developed in C++. The system performs closed-loop PI correction up to 100 Hz at a consumer-grade PC.Lee, Sunwoo;Park, Woojin;Han, Jimin;Ahn, Hojae;Kim, Yunjong;Lee, Dae-Hee;Kim, Geon Hee;Pak, Soojong 67.2
Not only the magnitude of the mirror surface error, the pattern matters as it produces certain aberrations. In particular, the surface error of the freeform mirrors, which are optimized to eliminate specific aberrations, might show much higher sensitivity in optical performance. Therefore, we analyze the mirror surface error with Zernike polynomials with the goal of generating a realistic error surface. We investigate the surface error of the freeform mirror fabricated by diamond turning machine to analyze the realistic tendency of the error. The surface error with 0.22 ㎛ root-mean-square value is fitted to the Zernike terms using the incremental fitting method, which increases the number of the fitting coefficients through steps. Furthermore, optical performance via surface error pattern based on Zernike terms is studied to see the influences of each term. With this study, realistic error surface generation may allow higher accuracy not only for the feasibility test but also for all tests and predictions using optical simulations.Ji, Tae-Geun;Park, Woojin;Han, Jimin;Kim, Dohoon;Lim, Gu;Jeong, Mankeun;Im, Myungshin;Pak, Soojong 67.3
A prime focus telescope, e.g., Schmidt telescope, has advantages especially for a wide field of view survey in astronomy. In this optical configuration, the camera is placed in front of the primary mirror. Since the installation of a typical filter wheel to the prime focus telescope causes serious obscuration of the incoming light, a customized filter device is required for high sensitivity images. In this poster, we present a new filter exchange mechanism, which can host four filters moving along quadrant directions. We plan to install this on the Celestron 36 cm Rowe-Ackermann Schmidt Astrograph (RASA 36) located at El Sause Observatory in Chile.Choi, Yeonho;Kim, Kang-Min;Park, Chan;Jang, Jeong-Gyun;Han, Inwoo;Lee, Byeong-Cheol;Jang, Bi-Ho;Lee, Jong-Ung;Jeong, Eui-Jeong;Park, Myeong-Gu 68.1
외계행성 대기 연구를 위한 투과스펙트럼 관측에 적합한 측분광기를 개발하고 있다. 이 측분광기의 광학적 특성은 380~685nm의 파장범위, FOV 10', R>~400이며, 슬릿부, collimator, VPH grism, imaging lens와 CCD로 구성되어 있는데, 보현산천문대 1.8m 망원경의 CIM(Cassegrain Interface Module)에 카트리지 방식으로 장착되어 사용한다. 그 중 doublet 렌즈 2개를 대칭으로 배치하여 초점거리 280mm가 되도록 만든 collimator는 슬릿을 통과한 f/8 입사광에서 지름 35 mm의 pupil을 만드는데, 이곳에 VPH grism을 설치하였다. collimator 렌즈는 axial spring과 radial spring으로 알루미늄 barrel에 고정하였다. 이 collimator barrel은 CIM에 쉽게 장탈착 할 수 있도록 모듈화 하였다. Collimator Barrel에 대한 구조 해석 결과, 망원경 이동에 따른 중력에 의한 변형은 충분히 작았다. Grism은 슬라이딩 형태로 장착되어 영상 확인도 가능하도록 설계하였다.Han, Jimin;Chang, Seunghyuk;Park, Woojin;Lee, Sunwoo;Ahn, Hojae;Kim, Geon Hee;Lee, Dae-Hee;Pak, Soojong 68.2
UVO-Multiband Polarizing Imager System (UVOMPIS) is an ultraviolet to visible light multi-wavelength polarization/imaging system for Compact Advanced Satellite. We developed Linear Astigmatism Free-Three Mirror System (LAF-TMS) D200F2 as an optical system of UVOMPIS which has an entrance pupil diameter of 200 mm, a focal ratio of 2, a field of view of 2° × 4°. LAF-TMS is a confocal off-axis reflecting telescope system that removes linear astigmatism, and its all mirrors (M1, M2, M3) are optimized with the freeform surface to reduce high-order aberrations. Through the sensitivity analysis and Monte-Carlo simulation as the tolerance analysis, we can confirm the feasibility of the system, relatively sensitive parameters (tilt, decenter, despace, surface RMS error), and considerations for optomechanical design. From the sensitivity analysis, we can discover the relatively sensitive optical alignment parameters to a single perturbation. Further more, in the monte-carlo simulation, we investigate the minimum tolerance budget satisfying the required optical performance and whether the tolerance range is satisfied within manufacturing error.We develop a series of N-body data challenges, functional to the final analysis of the extended Baryon Oscillation Spectroscopic Survey (eBOSS) Data Release 16 (DR16) galaxy sample, primarily based on high-fidelity catalogs constructed from the Outer Rim simulation. We generate synthetic galaxy mocks by populating Outer Rim halos with a variety of halo occupation distribution (HOD) schemes of increasing complexity, spanning different redshift intervals. We then assess the performance of three complementary redshift space distortion (RSD) models in configuration and Fourier space, adopted for the analysis of the complete DR16 eBOSS sample of Luminous Red Galaxies (LRGs). We find that all the methods are mutually consistent, with comparable systematic errors on the Alcock-Paczynski parameters and the growth of structure, and robust to different HOD prescriptions - thus validating the robustness of the models and the pipelines used for the baryon acoustic oscillation (BAO) and full shape clustering analysis. Our study is relevant for the final eBOSS DR16 'consensus cosmology', as the systematic error budget is informed by testing the results of analyses against these high-resolution mocks. In addition, it is also useful for future large-volume surveys, since similar mock-making techniques and systematic corrections can be readily extended to model for instance the DESI galaxy sample.While Dark Energy is one of the explanations for the accelerating expansion of the Universe, its nature remains a mystery. The standard (flat) ΛCDM model is consistent with cosmological observations: type Ia Supernova, BAO, CMB, and so on. However, the analysis of observations assuming a model, model-dependent approach, is likely to bias the results towards the assumed model. In this poster, I will introduce model-independent approach with Gaussian process and the application of Gaussian process regression to reconstruct the equation of state of dark energy.Bong, Su-Chan;Yang, Heesu;Lee, Jae-Ok;Kim, Jinhyun;Jeon, Young-Beom;Jang, Bi-Ho;Seough, Jungjoon;Park, Young-Deuk 69.2
Korea Astronomy and Space Science Institute (KASI) is developing a coronagraph to measure the coronal electron density, temperature, and speed utilizing spectral change of the K-corona around 400 nm. However, near UV light is more affected by atmospheric effect on the ground than visible light. For the total solar eclipse on July 2 2019, KASI organized an expedition team to test the possibility of the similar measurement scheme in the visible light. The observation site was in Las Flores, San Juan, Argentina. We built an imaging spectrograph using micro lenslet array and grism, named Coronal Integral Field Spectrograph (CorIFS). In addition, images of white light corona, wide field background, and all sky were taken with various camera settings. We present the preliminary results of the expedition.Yang, Heesu;Choi, Seonghwan;Lim, Eun-Kyung;Kim, Jihun;Park, Jongyeob;Baek, Ji-Hye;Cho, Kyung-Suk;Kim, Yeon-Han;Jang, Bi-Ho;Kwon, Ryun-Young;Kim, Rok-Soon;Kim, Sujin;Park, Yeong-Deuk;Bong, Suchan;Seough, Jungjoon;Kwak, Young-Sil 69.3
우주개발과 활용이 주요 화두가 된 현대에 보다 빠르고 정확한 우주환경 예보는 전략적으로 매우 중요하다. 이에 우리는 광대역태양영상분광망원경(Wide-Field Solar Spectro-Imaging Telescope, Post SOlar Flare Telescope: PSOFT)을 활용한 태양전면 영상분광감시체계를 구성하고자 한다. 전세계 세 곳에 PSOFT를 배치하여 우주환경에 중대한 영향을 주는 요소인 태양의 플레어와 홍염 분출과 같은 현상과 표면의 다양한 활동들을 실시간으로 관측 분석하고자 한다. PSOFT는 30cm 구경의 광학계에 고속영상분광기를 결합하여 태양 전면의 분광영상을 약 1초각의 영상해상도와 5분의 시간해상도로 획득한다. 태양 전면을 슬릿으로 스캔하는 방식으로 H alpha와 Ca II 854.2nm선의 분광정보를 획득하는데 팁틸트 미러를 이용하여 1차적인 시상보정과 함께 스캔모션을 함께 구현함으로써 1)광학계 구조를 단순화하고, 2) 빠른 스캔이 가능하다. PSOFT로 얻은 태양전면 채층분광영상 데이터는 정밀한 우주환경 예보에 필요한 플레어나 홍염분출의 발생초기 정보를 제공할 뿐 아니라 태양 저층대기에서 발생하는 자기재연결, 파동 등에 대한 통계적 연구자료를 제공할 것으로 기대한다.Raman-scattered He II features are known to be present in several young planetary nebulae (PNe) including NGC 7027, NGC 6302, IC 5117 and NGC 6790. These features provide a new spectroscopic window to probe both thick neutral regions and far UV regions near Lyman series. We carry out photoionization model calculations using 'CLOUDY' to explore He II emission strengths dependent on the physical conditions of the central star. The emission nebula is treated as a simple spherical shell with uniform density. It is found that detectable Raman-scattered He II are obtained for T∗ ~ 105 K in the presence of a thick neutral component. We present mock spectra exhibiting Raman He II features based on the photoionization calculations and compare them with observed data. We discuss effective strategies for searching young PNe with Raman-scattered He II emissivities.A type IIb supernova (SN IIb) is the result of core-collapse of a massive star which lost most of its hydrogen-rich envelope during its evolution. The pre-SN progenitor properties, such as the total radius and the mass of the hydrogen-rich envelope, can widely vary due to the mass-loss history of the progenitors. Optical light curves of SNe IIb are dominated by energy released by the hydrogen recombination and the radioactive decay of 56Ni in the early and late epochs respectively. This may result in distinctive double peaked light curves like the one observed in SN 1993J. The first peak, caused by the hydrogen recombination, can be modelled with numerical simulations providing information on the pre-SN progenitor properties. We compare two radiation-hydrodynamics codes, STELLA and SNEC, that are frequently used in SNe modelling, and investigate the effect of opacity treatment on the temporal evolution of the color temperature of SNe and eventually on the optical light curves. We find that with a proper treatment of the scattering opacity, SNe IIb models exploded from the progenitor models evolved with latest stellar evolution model hardly match the observational data. We also discuss the smaller scale features found in the models during hydrogen recombination phase.공생별의 밝기 변화와 분광선 변화에 대한 지속적인 관측과 분석은 공생별 구성원의 구조, 거성으로부터의 질량 이동, 백색왜성 근처에서의 부착원반 형성과 이들의 진화에 대한 중요한 정보를 제공한다. 본 연구에서는 보현산 천문대 1.8-m 망원경과 고분산 에셀분광기 BOES를 이용하여 타 연구자에 의해 하룻밤 새 분광선 변화가 있다고 보고된 공생별 CH Cyg를 중심으로 AG Dra와 EG And의 방출선들에 대한 하룻밤 새 변화 모니터링 관측을 수행하였고, 이 세 공생별의 짧은 시간 내 분광적 변화 양상과 특성을 파악하고자 한다.Previous numerical simulations on planet-disk interactions revealed a lot of interesting phenomena including the planetary migration and the formation of many sub-structures inside the disks. However, these simulations were limited to an isothermal or adiabatic equation of state which does not account for various heating and cooling processes in the disks. Recent studies showed that the behavior of the planet-disk interaction can be significantly influenced by the disk thermodynamics. We develop a radiative diffusion module based on the two-temperature flux-limited diffusion approximation accounting for viscous heating and the accretion feedback. In this presentation, we describe our radiative diffusion solver, present some test results, and discuss potential applications of the module to planet-disk interactions,One of the distinctive characteristics of the evolution of binary systems would be mass transfer. Close binary systems experience so-called Case A mass transfer during the main-sequence. We have performed calculations of the evolution of massive Case A (with the initial period 1.5 ~ 4.5 days) binary systems with the initial mass of 10 ~ 20 solar masses and mass ratio 0.5 ~ 0.95 using the MESA code. We find that in some systems, after the first mass transfer, the secondary stars evolve faster than the primary stars and undergo so-called 'reverse' mass transfer. Such phenomena tend to occur in relatively low-mass (initial mass < 16 solar masses) and close (initial period < 3 day) systems. Unless a system enters the common-envelope phase, the primary star would become a single helium star after the secondary star ends its life if the system were unbound by the neutron star kick. We find the various evolutionary implications of the remaining primary stars. In addition to the evolution into the compact single helium star progenitor, there is a possibility that the remaining primary star could evolve into a helium giant star, which could be a promising candidate for Type Ibn supernova progenitor, depending on the core mass. Further, we find that some primary stars satisfy the conditions for the formation of electron-capture supernova progenitor.
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