천문학회보 (The Bulletin of The Korean Astronomical Society) (The Bulletin of The Korean Astronomical Society)
한국천문학회 (The Korean Astronomical Society)
- 반년간
- /
- 1226-2692(pISSN)
과학기술표준분류
- 지구과학(지구/대기/해양/천문) > 천문학
제38권2호
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우리는 밝기(측광)나 스펙트럼(분광) 관측 자료가 시간에 따라 변하는 변광천체(variable objects)의 시간적 변화 현상을 분석하여 우주의 기본 구성요소인 별뿐만 아니라, 외계행성의 물리적 특성을 규명할 수 있다. 이 천체 중에서 두 개의 별이 중력으로 묶여 서로 공전하면서 주기적으로 식을 일으키며 밝기가 변하는 항성계를 식쌍성이라 하고, 같은 원리로 행성이 별의 표면을 가로질러 횡단하면서 별빛을 가려 어두워지는 방법에 의해 발견된 행성을 별표면 통과 행성(transiting planets)이라고 한다. 쌍성 연구는 이전에 주류를 이루었던 천문학적 기본변수(별의 질량, 반경, 밝기 등)의 결정 연구에서 보다 정밀한 다파장 관측에 의한 천문학적 특이현상의 검출과 분석 연구로 점차 변화해 가고 있다. 이 강연에서는 근접쌍성계의 여러 특이현상 중에서 광도와 궤도공전주기 변화를 보이는 식쌍성들의 최근 연구결과를 제시하고자 한다. 이와 더불어, 쌍성의 분석방법을 활용한 쌍성계 주위를 공전하는 외계행성계(circumbinary planets)의 최초 발견 및 별표면 통과 행성의 물리적 특성에 대하여 논의하고자 한다.
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The Korean VLBI Network (KVN) as a world-first multi-frequency VLBI system is operated at four bands of 22, 43, 86, and 129 GHz simultaneously. The performances of both single dish and VLBI network were already confirmed through single dish researches and VLBI evaluation test observations. The VLBI common use of the KVN at 22/43 GHz bands has been started from this autumn. The combined network of KVN and Japanese VERA (KaVA) will start the common use from the first half of next year. Here we present several observational results in the fields of star forming regions, late-type stars, and active galactic nuclei using the KVN and KaVA. The fringes of 44 GHz
$CH_3OH$ (Class I) masers were detected from 26 sources for the first time using the KVN and imaging observations are under performing. Simultaneous observations of SiO and$H_2O$ masers toward about 1000 evolved stars showed the different maser properties between SiO and$H_2O$ masers according to the evolutionary stages of AGB and post-AGB stars. The catalog of correlated flux densities were established from a 43 GHz (Q-band) survey of 637 extragalactic sources. At 22 GHz (K-band), flux density measurement and fringe survey for new sources were performed toward a large number of sources. In addition, the large program of KVN and/or KaVA under planning is introduced. -
We are developing empirical space weather (solar flare, solar proton event, and geomagnetic storm) forecast models based on solar data. In this talk we will review our main results and recent progress. First, we have examined solar flare (R) occurrence probability depending on sunspot McIntosh classification, its area, and its area change. We find that sunspot area and its increase (a proxy of flux emergence) greatly enhance solar flare occurrence rates for several sunspot classes. Second, a solar proton event (S) forecast model depending on flare parameters (flare strength, duration, and longitude) as well as CME parameters (speed and angular width) has been developed. We find that solar proton event probability strongly depends on these parameters and CME speed is well correlated with solar proton flux for disk events. Third, we have developed an empirical storm (G) forecast model to predict probability and strength of a storm using halo CME - Dst storm data. For this we use storm probability maps depending on CME parameters such as speed, location, and earthward direction. We are also looking for geoeffective CME parameters such as cone model parameters and magnetic field orientation. We find that all superstorms (less than -200 nT) occurred in the western hemisphere with southward field orientations. We have a plan to set up a storm forecast method with a three-stage approach, which will make a prediction within four hours after the solar coronagraph data become available. We expect that this study will enable us to forecast the onset and strength of a geomagnetic storm a few days in advance using only CME parameters and the WSA-ENLIL model. Finally, we discuss several ongoing works for space weather applications.
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Globular clusters (GCs) are among the oldest stellar objects in the universe and provide valuable constraints on many aspects of galaxy evolution. GC systems typically exhibit bimodal color distributions the phenomenon of which has been a major topic in the area of GC research. GC color bimodality established a paradigm where scenarios to explain its origin require two GC groups with different formation origins. The GC division, asserted mainly by photometric color bimodality so far, has been viewed as the presence of two distinct metallicity subgroups within individual galaxies. In this study, we make use of spectroscopy of GC systems associated with two giant galaxies, M31 (the Andromeda) and M87 (NGC 4486), to investigate the GC bimodality and the underlying metallicity distributions. Recent spectroscopy on the globular cluster (GC) system of M31 with unprecedented precision witnessed a clear bimodality in absorption-line index distributions of old GCs. Given that spectroscopy is a more detailed probe into stellar population than photometry; the discovery of index bimodality may point to the very existence of dual GC populations. However, here we show that the observed spectroscopic dichotomy of M31 GCs emerges due to the nonlinear nature of metallicity-to-index conversion and thus one does not necessarily have to invoke two separate GC subsystems. We present spectra of 130 old globular clusters (GCs) associated with the Virgo giant elliptical galaxy M87, obtained using the Multi-Object Spectrography (MOS) mode of Faint Object Camera and Spectrograph (FOCAS) on the Subaru telescope. M87 GCs with reliable metallicity measurements exhibit significant inflection along the color-metallicity relations, through which observed color bimodality is reproduced from a broad, unimodal metallicity distribution. Our findings lend further support to this new interpretation of the GC color bimodality, which could change much of the current thought on the formation of GC systems and their host galaxies.
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Park, Dawoo;Woo, Jong-Hak;Romero-Colmenero, Encarni;Crawford, Steven M.;Barth, Aaron J.;Pei, Liuyi 54
We performed spectroscopic and photometric monitoring observations of a QSO, PG0934+013 for a reverberation-mapping analysis, using the 9-m Southern African Large Telescope (SALT) for spectroscopy and the 2-m Faulkes Telescope North and the South for photometry. The monitoring campaign was carried out for 5 month between December 2012 to April 2013, providing 20 spectroscopic epochs and ~40 photometric epochs. Based on the obtained spectra, which typically have a signal-to-noise ratio to 30-60, we performed multicomponent decomposition using various components, i.e., power-law continuum, FeII emission complex, and broad and narrow emission lines, to properly measure the Hbeta line flux. After a flux normalization using [O III] 5007 line luminosity, we obtained a rms spectrum from all epochs, which shows clear variability of Hbeta line. We find that Hbeta line flux decreases by ~20% during the monitoring period while the continuum flux obtained from the aperture photometry based on the imaging data, shows similar variability. The current Hbeta light curve shows monotonic decrease and a reliable cross correlation analysis between Hbeta and continuum light is difficult. Nevertheless, we obtained a preliminary lag measurements as ~24 light days. -
Recent observations have shown that some massive globular clusters (GCs) host multiple stellar populations having different heavy element abundances enriched by supernovae. They usually accompany multiple red giant branches (RGBs) in the color-magnitude diagrams (CMDs), and are distinguished from most of the other GCs which display variations only in light element abundances. In order to investigate the star formation histories of these peculiar GCs, we have constructed synthetic CMDs based on the updated versions of Yonsei.Yale (
$Y^2$ ) isochrones and horizontal branch evolutionary tracks which include the cases of enhancements in both helium and the total CNO abundances. To estimate ages and helium abundances of subpopulations in each GC, we have compared our models with the observations on the Hess diagram by employing a${\chi}^2$ minimization technique. In this talk, we will present our progress in the population modeling for these GCs with multiple RGBs. -
The current hierarchical model of galaxy formation predicts that galaxy halos contain merger relics in the form of long stellar streams. In order to find stellar substructures in galaxy, we focused our investigation on the stellar spatial density around globular clusters and on the quantitative properties of the evolved sequences in the color-magnitude diagrams (CMDs). First, we investigated the spatial configuration of stars around five metal-poor globular clusters in halo region (M15, M30, M53, NGC 5053, and NGC 5466) and one metal-poor globular cluster in bulge region (NGC 6626). Our findings indicate that all of these globular clusters show strong evidence of extratidal features in the form of extended tidal tails around the clusters. The orientations of the extratidal features show the signatures of tidal tails tracing the clusters' orbits and the effects of dynamical interactions with the galaxy. These features were also confirmed by the radial surface density profiles and azimuthal number density profiles. Our results suggest that these six globular clusters are potentially associated with the satellite galaxies merged into the Milky Way. Second, we derived the morphological parameters of the red giant branch (RGB) from the near-infrared CMDs of 12 metal-poor globular clusters in the Galactic bulge. The photometric RGB shape indices such as colors at fixed magnitudes, magnitudes at fixed colors, and the RGB slope were measured for each cluster. The magnitudes of the RGB bump and tip were also estimated. The derived RGB parameters were used to examine the overall behavior of the RGB morphology as a function of cluster metallicity. The behavior of the RGB shape parameters was also compared with the previous observational calibration relation and theoretical predictions of the Yonsei-Yale isochrones. Our results of studies for stellar spatial distribution around globular clusters and the morphological properties of RGB stars in globular clusters could add further observational evidence of merging scenario of galaxy formation.
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대규모 광도곡선 자료에서 다양한 주기변광성들의 정확한 주기를 효율적으로 검출하는 실험을 시도하였다. 실험을 위해 OGLE-III 맥동 변광성(RR Lyrae, Delta Scuti, Cepheid) 목록 중, I 필터로 관측된 총 31,324개의 광도 곡선을 사용하였다. 이 실험에 사용한 주기분석 알고리즘 MS_Period(Multi-Step period searching method)는 주기를 놓치지 않기 위해 두 가지 다른 방법(Multi Polynomial function, Phase Dispersion)으로 후보 주기를 구하고 정밀주기를 도출하기 위해 후보 주기 주변부를 Spline fitting을 통해 재탐색하는 방법이다. 기존의 MS_Period 방식은 주기 탐색 간격(dP/P)이 일정하였으나, 우리는 탐색 주기 구간을 나누고 짧은 주기에서는 작은 간격으로, 긴 주기에서는 보다 넓은 간격으로 주기를 탐색하는 과정을 추가하였다. 그 결과 98% 이상의 별에서 OGLE-III와 거의 일치하는 주기를 얻었으며, 긴 주기에서의 불필요한 정밀 탐색을 회피함으로써 분석시간도 단축되었다. 주기 결정이 어려운 경우들은 주로 1) periodogram에서 실제 주기가 아닌 1일 근처에서 noise보다 큰 peak가 보이는 경우, 2) 하나의 별에 대해 여러 주기가 비슷한 Phase diagram을 보이고, periodogram에서도 비슷한 peak를 갖는 경우, 3) OGLE-III의 주기와 전혀 다른 주기만 찾은 경우, 4) OGLE-III에서 제시하지 않은 혼합된 주기의 존재가 의심되는 경우인 것을 확인하였고, 각 사례들의 특징을 살펴보았다.
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태양의 활동영역에서 관측할 수 있는 흑점은 주로 흑점군으로 관측되며, 태양폭발현상의 발생을 예보하기 위한 중요한 관측 대상 중 하나이다. 현재 태양 폭발을 예보하는 모델들은 McIntosh 흑점군 분류법을 사용하며 통계적 모델과 기계학습 모델로 나누어진다. 컴퓨터는 흑점군의 형태학적 특성을 연속적인 값으로 계산하지만 흑점군의 형태적 다양성으로 인해 McIntosh 분류법과 일치하지 않는 경우가 있다. 이러한 이유로 컴퓨터가 계산한 흑점군의 형태학적인 특성을 예보에 직접 적용하는 것이 필요하다. 우리는 흑점군을 검출하기 위해 최소신장트리(Minimum spanning tree : MST)를 이용한 계층적 군집화 기법을 수행하였다. 그래프(Graph)이론에서 최소신장트리는 정점(Vertex)과 간선(Edge)으로 구성된 간선의 가중치의 합이 최소인 트리이다. 우리는 모든 흑점을 정점, 그들의 연결을 간선으로 적용하여 최소신장트리를 작성하였다. 또한 최소신장트리를 활용한 계층적 군집화기법은 초기값에 따른 군집화 결과의 차이가 없기 때문에 흑점군 검출에 있어서 가장 적합한 알고리즘이다. 이를 통해 흑점군의 기본적인 형태학적인 특성(개수, 면적, 면적비 등)을 계산하고 최소신장트리를 통해 가장 면적이 큰 흑점을 중심으로 트리의 깊이(Depth)와 차수(Degree)를 계산하였다. 이 방법을 2003년 SOHO/MDI의 태양 가시광 영상에 적용하여 구한 흑점군의 내부 흑점수와 면적은 NOAA에서 산출한 값들과 각각 90%, 99%의 좋은 상관관계를 가졌다. 우리는 이 연구를 통해 흑점군의 형태학적인 특성과 더불어 예보에 직접적으로 활용할 수 있는 방법을 논의하고자 한다.
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If the magnetic field is extremely strong, as in pulsar/black hole magnetospheres, the Alfven speed approaches to the speed of light and we need relativity to describe interactions of Alfvenic waves. In this poster, we discuss physics of Alfvenic turbulence in this limit. We first discuss interaction of Alfvenic wave packets and scaling relations of resulting turbulence. Then we show results of numerical simulations. Finally we compare relativistic Alfvenic turbulence and its Newtonian counterpart.
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Yamagishi, Mitsuyoshi;Kaneda, Hidehiro;Oyabu, Shinki;Ishihara, Daisuke;Onaka, Takashi;Shimonishi, Takashi;Suzuki, Toyoaki;Minh, Young Chol 34.1
Interstellar ices (e.g.,$H_2O$ ,$CO_2$ , and CO ices) are formed on the surface of dust grains in dense molecular clouds. In a near-infrared spectrum, we can observe deep absorption features particularly due to$H_2O$ ice at$3.05{\mu}m$ and$CO_2$ ice at$4.27{\mu}m$ . These interstellar ices have many pieces of information on the interstellar environment. Among various ices,$CO_2$ ice is one of the most important ones as a probe of the interstellar environment. That is because$CO_2$ ice is a secondary product unlike$H_2O$ and CO ices which are primarily formed on dust grains. Past studies for$CO_2$ ice in nearby galaxies were performed only for the galactic center in a few galaxies. In order to utilize the information from$CO_2$ ice effectively, it is valuable to perform mapping observations of ices on a galactic scale. With AKARI, we obtain the spatially-resolved near-infrared ($2.5-5.0{\mu}m$ ) spectra for the central ~1 kpc region of the nearby starburst galaxy M 82. These spectra clearly show the absorption features due to interstellar$H_2O$ and$CO_2$ ices, and we created their column density maps. As a result, we find that the spatial distribution of$H_2O$ ice is significantly different from that of$CO_2$ ice;$H_2O$ ice is widely distributed, while$CO_2$ ice is concentrated near the galactic center. Our result for the first time reveals spatial variations in$CO_2/H_2O$ ice abundance ratio on a galactic scale, suggesting that the ice-forming interstellar environment changes within a galaxy. In this presentation, we discuss the cause of the variations in the ice abundance ratio. -
Star formation beyond the galaxy discs and the principles governing it have attracted a lot of recent attention and the advent of ultraviolet (UV) and mid-infrared (MIR) telescopes like the GALEX and Spitzer have enabled major advances in such studies. In order to study the HI gas properties such as the morphology, kinematics and column density distributions, and their correlation with the star forming zones, especially in the tidal bridges, tails and debris, we carried out an HI survey of a set of Spitzer-observed interacting systems using the Giant Metrewave Radio Telescope (GMRT). Here we present results from three of these systems, Arp86, Arp181 and Arp202. In Arp86, we detect excellent star-gas correlation in the star forming tidal bridges and tails. In Arp181, we find the two interacting galaxies to be highly gas depleted and the entire gas of the system is found in the form of a massive tidal debris about 70 kpc from the main galaxies. In all three cases, Arp86, Arp181 and Arp202, the tidal debris seem to host ongoing star formation. We also detect three new candidate tidal dwarf galaxies (TDG) in these systems with large quantities of gas associated with them.
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By probing nuclear regions and overall properties of AGN hosts as a function of their environments, we aim to observationally examine how AGN activities are related to their surroundings. We have selected eight representative AGN hosts in the Virgo cluster, including seven cluster members (M49, M60, M84, M87, NGC 4435, NGC 4526, NGC 4636) and one galaxy that is likely to be background (NGC 4261) but still close enough to be studied in high resolution. The selected galaxies are located in a range of density regions showing various morphology in 1.4 GHz continuum. High resolution observations with the KVN allow us to access the inner region of the AGN without suffering from dust extinction and synchrotron self-absorption. Since half of our targets are weak to be detected at K-band within its coherence time, we applied phase referencing (fast antenna position switching) to calibrate fast atmospheric phase fluctuations. We successfully detected relatively bright AGNs, such as M87, M84 and NGC4261, but no detection signature was found to the other members of the sample. In this talk, we will present our first results from our KVN observations, while we will discuss in detail the applied technique and our immediate future plans.
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I will present a new approach to constrain galaxy physical parameters from the combined interpretation of stellar and nebular emission in wide ranges of observations. This approach relies on a comprehensive library of synthetic spectra, assembled using state-of-the-art models of star formation and chemical enrichment histories, stellar population synthesis, nebular emission and attenuation by dust. We focus on the constraints set by 5-band photometry and low- and medium-resolution spectroscopy at optical rest wavelengths on a few physical parameters characterizing the stars and interstellar medium. Since these parameters cannot be known a priori for any galaxy sample, we assess the accuracy to which they can be retrieved by simulating 'pseudo-observations' using models with known parameters. We find that the combined analysis of stellar and nebular emission in low-resolution (50A FWHM) galaxy spectra provides valuable constraints on all physical parameters. The approach can be extended to the analysis of any type of observation and during this talk i will present some applications to observed galaxies up to redshift 1.5.
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We present our study of analyzing the photometric properties of the globular cluster (GC) system which resides in the extended halo of the central bright Coma cluster galaxy NGC 4874. The core of the Coma cluster of galaxies (Abell 1656) was observed with both the HST Advanced Camera for Surveys (ACS) in the F475W (g475) and F814W (I814) and Wide Field Camera 3 IR Channel (WFC3/IR) in the F160W (H160) filters. The data analysis procedure and GC candidate selection criteria are briefly described. We investigate the interesting "tilt" features in color-magnitude diagrams for this GC system and their link to the nonlinear color-metallicity relation for GCs. The NGC 4874's GC system exhibits a bimodal distribution in the optical g475-I814 color and much more than half the GCs fall in the red side at g475-I814 ~ 1.1. This bimodality is weakened in the optical-IR I814-H160 color; the quantitative analysis on the features of both color distributions using the Gaussian Mixture Modeling code proves the bimodalities are different. Both colors, thus, cannot linearly reflect the bimodality of an underlying metallicity, supporting the suggestion that observed bimodalities in extragalactic GC colors are the metallicity-to-color projection effect.
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Recently it turns out that simple-looking elliptical galaxies and lenticular galaxies are more complex and intriguing than expected. One of the most surprising and intriguing findings in extragalactic studies during the last two decades is a discovery that color distribution of the globular clusters in these galaxies is bimodal, suggesting that there are two subpopulations: blue and red globular clusters. We present a determination of the two-dimensional shape parameters of the blue and red globular cluster systems (GCSs) in a large number of bright elliptical galaxies and lenticular galaxies. The position angles of both and red GCSs show a correlation with those of the stellar light distribution, showing that the major axes of the GCSs are well aligned with those of their host galaxies. However, the shapes of the red GCSs show a tight correlation with the stellar light distribution as with the rotation property of their host galaxies, while the shapes of the blue GCSs do much less. These provide clear geometric evidence that the origins of the blue and red globular clusters are distinct and that these galaxies may have dual halos: a blue (metal-poor) halo and a red (metal-rich) halo. These two halos show significant differences in metallicity, structure, and kinematics, indicating that they are formed in two distinguishable ways. The red halos might have formed via dissipational processes with rotation, while the blue halos are through accretion.
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We present the Yonsei evolutionary population synthesis (YEPS) models based on the high-resolution empirical spectral energy distributions (SEDs). We have adopted the MILES library in the optical wavelength, and our new models based on the MILES library show good agreements with our previous models presented in the YEPS I. The effect of hot horizontal-branch (HB) stars on the integrated properties of simple stellar populations (SSPs) is again confirmed by our models based on empirical SEDs. In addition, we have extended our empirical models to the near-IR wavelength and predicted the strengths of the calcium II triplet (CaT) and the Paschen triplet (PaT) based on the INDO-US and the Cenarro library. We find that the effect of HB stars and the age of SSPs on the CaT is almost negligible. On the other hands, the PaT models are very sensitive to the existence of hot stars, e.g., HB stars and young turn-off stars, and show very similar results with Balmer lines. Interestingly, the CaT distribution of GCs in NGC 1407, which is at odds with the optical (B-I) color distribution, can be explained by the unique feature of the CaT-[Fe/H] relations that show almost the same equivalent widths in the metal-rich regime. We will also discuss the impact of the second-generation populations on the strength of the CaT.
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Several studies have reported the presence of sodium excess objects having neutral atomic absorption lines at
$5895{\AA}$ (NaD) and$8190{\AA}$ that are deeper than expected based on stellar population models that match the stellar continuum. The origin of these lines is therefore hotly debated. van Dokkum & Conroy proposed that low-mass stars (0.3M) are more prevalent in massive early-type galaxies, which may lead to a strong NaI 8190 line strength. It is necessary to test this prediction, however, against other prominent optical line indices such as NaD, Mgb, and Fe5270, which can be measured with a significantly higher signal-to-noise ratio than NaI 8190. We identified a new sample of roughly one thousand NaD excess objects (NEOs; ~8% of galaxies in the sample) based on NaD line strength in the redshift range 0.00${\alpha}$-enhanced" ([ ${\alpha}/Fe$ ] ~ 0.3), "metal-rich" ([Z/H] ~ 0.3), and, especially, "Na-enhanced" ([Na/Fe] ~ 0.3). -
We use high-resolution hydrodynamic simulations to study nonlinear gas responses to imposed non-axisymmetric stellar potentials in barred-spiral galaxies. The gas is assumed to be infinitesimally thin, isothermal, and unmagnetized. We consider various spiral-arm models with differing strength and pattern speed, while fixing the bar parameters. We find that the extent and shapes of spiral shocks as well as the related mass drift depend rather sensitively on the pattern speed. In models where the arm pattern is rotating more slowly than the bar, the gaseous arms extend from the bar ends all the way to the outer boundary, with a pitch angle slightly smaller than that of the stellar counterpart. The arms drive mass inflows at a rate of
${\sim}0.5-2.5M{\odot}/yr$ to the bar region to which the shock dissipation, external torque, and self-gravitational torque contribute about 50%, 40%, and 10%, respectively. About 85% of the inflowing mass is added to bar substructures such as an inner ring, dust lanes, and a nuclear ring. while the remaining 15% encircles the bar region. On the other hand, models where the arms corotate with the bar exhibit mass outflows, rather than inflows, over most of the arm region. In these models, spiral shocks are much more tightly wound than the stellar arms and cease to exist in the region where$M{\bot}/sinp*{\geq}25-40$ , where$M{\bot}$ denotes the Mach number of a rotating gas perpendicular to the arms with pitch angle p*. We demonstrate that the distributions of line-of-sight velocities and densities can be a useful diagnostic tool to distinguish if the arms and bar corotate or not. -
We use grid-based hydrodynamic simulations to study star formation history in nuclear rings of barred-spiral galaxies. In our previous study, we concentrated on bar-only galaxies without spirals, finding that the star formation rate (SFR) in a nuclear ring exhibits a strong primary burst at early time before decreasing to below 1
$M_{\odot}/yr$ at late time. The rapid decline is caused by the paucity of the gas in the bar region, due to early massive gas inflows to the nuclear ring. Since star formation in nuclear rings is observed to be sustained for about 1-2 Gyr, this requires mechanisms to supply the gas to the bar regions. In this work, we study the effect of spiral arms on the radial gas inflows and related star formation in the nuclear rings. We show that spiral arms are efficient to remove angular momentum of the gas to cause significant gas inflows to the bar region, provided the patten speed of the arms is much smaller than that of the bar. The inflowing gas is added to a nuclear ring, making the ring SFR episodic over a long period of time. The time interval of multiple bursts of star formation is a few tens to hundred million years, with the mean peak SFR of${\sim}5M_{\odot}/yr$ , consistent with observations of M100. -
We perform a set of N-body/SPH simulations of galaxy interactions between early- and late-type galaxies with the mass ratio of 2 to 1. We show that mass transfer during a fly by interaction (the closest approach distance ~50kpc) can cause the morphology transformation of an early-type galaxy to a late type. In our simulations, we vary the orbital parameters of the interactions and the cold gas fraction of the late-type galaxy to compare how the morphology transformation is affected by the amount of mass transfer and orbital angular momentum of cold gas accreted to the early type. We also include hot halo gas in the galaxy models and show the location of the tidal bridge can be influenced by the shock generated during the collision.
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Although galaxy mergers are thought to play an important role in forming elliptical galaxies, mergers in galaxy clusters have drawn less attention compared to mergers in field environments because galaxies with high peculiar velocities are unlikely to merge with each other. However, comparable fractions of merger features in cluster galaxies have been reported from deep imaging of Abell clusters, suggesting the relevance of mergers in the transformation of cluster early-type galaxies (Sheen et al. 2012). As a more direct approach to understanding the origin of tidal features in clusters, we perform hydrodynamic re-simulations on a cluster of galaxies. Based on mock observation images of the simulated cluster galaxies, we construct and analyze the cluster early-type galaxy sample in a consistent manner with Sheen et al. 2012. We find that the fraction of tidal feature from the simulated cluster is comparable to that of the observation. Evolutionary history of the galaxies with merger features shows that most of the mergers responsible for the merger features in the present originate from outside the cluster more than 2Gyrs ago. We also find that many of the galaxies with tidal features show correlations with subgroups in the cluster. All these results suggest that merger features in the cluster are due to preprocessing before accretion into the cluster.
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Lee, Joon Hyeop;Lee, Hye-Ran;Kim, Minjin;Seon, Kwang-Il;Ree, Chang Hee;Kim, Sang Chul;Lee, Jong Chul;Jeong, Hyunjin;Ko, Jongwan;Yang, Soung-Chul;Choi, Changsu 41.1
To test whether the close relationships between host and satellite galaxies in isolated groups are also found in the harsh environment of a galaxy cluster, we carry out a case study of WHL 085910.0+294957, a galaxy cluster at z=0.30, using deep images obtained with the 2.1-m Otto Struve telescope and CQUEAN CCD camera. When environmental parameters are controlled, the local weighted mean color of faint galaxies shows a measurable correlation with the color of their bright ($M_i$ < -18) neighbor. The most striking result is that the red (r - i > 0.2) and bright galaxies within 200 kpc distance from the center of the cluster are correlated in color with very faint ($M_i$ > -14) galaxies around them by$(r-i)_{satellites}=(7.276{\pm}1.402){\times}(r-i)_{host}-2.434$ (correlation coefficient = 0.665). We suggest three scenarios to interpret the results: vestiges of infallen groups, dwarf capturing, and tidal tearing of bright galaxies. -
We present a very wide-field survey of dwarf galaxies in the M106 Group using the Sloan Digital Sky Survey Data Release 8, covering an area of
$10^{\circ}{\times}14^{\circ}$ around M106. We select 18 new members of the M106 group, 10 of which are new findings. Surface brightness profiles of most of these galaxies are fitted well by an exponential law. Twelve of these galaxies are early-types, and the rest are late-types. We produce a master catalog of the M106 Group galaxies by combining these new galaxies with 30 known galaxies. The faint-end of the luminosity function of these galaxies is fitted by a power law with an index${\alpha}=-1.22{\pm}0.02$ . This slope is much flatter than the value predicted by the${\Lambda}CDM$ models, but is similar to the values for other galaxy groups. The spatial distribution of the dwarf galaxies in the M106 group is quite different from that of the bright members of the group, requiring a further study. -
GRB 100205A is a Gamma Ray Burst (GRB) which is suspected to be at
$11{\leq}Z{\leq}13.5$ due to its very red H-K color ($(H-K)_{vega}=2.1{\pm}0.5$ ). We observed a field centered at GRB 100205A with the Wide Field Camera (WFCAM) at the United Kingdom Infrared Telescope (UKIRT) in Hawaii, so as to find a 11 < z < 13 quasar that could be located around the GRB. The images were obtained in J, H, and K filters covering a square area of 0.75$deg^2$ to the depths of 22.5, 21.4, and 20.2 in Vega magnitude at$5{\sigma}$ , respectively. Also using a z-band image observed by MegaCam in Canada France Hawaii Telescope (CFHT), we found 12 candidates that have colors consistent with a quasar at 11 < z < 13 with two criteria; (1) non-detection in z-, J-bands and$(H-K)_{vega}$ > 1.6 (2) only detection in K-band with$(Hlimit-K)_{vega}$ > 1.6. However, we also find 627 red ($(H-K)_{vega}$ > 1.4) objects that are likely to be old or dusty galaxies at$z{\leq}3$ , so the 12 candidates could be these red objects. These red objects are found to be strongly clustered in the Ultra Deep Survey (UDS) fields of UKIRT Infrared Deep Sky Survey (UKIDSS) than those in the GRB 100205A field. We suggest a lack of a strongly clustered region surrounding an extremely high-redshift GRB with some limitations. -
Park, Daeseong;Woo, Jong-Hak;Treu, Tommaso;Bennert, Vardha N.;Malkan, Matthew A.;Auger, Matthew W. 42.2
We investigate the cosmic evolution of the black hole mass-bulge luminosity relation with a sample of 52 moderate-luminosity AGNs at$z{\simeq}0.36$ and$z{\simeq}0.57$ , corresponding to look-back times of 4 and 6 Gyrs. By employing robust multi-component spectral and structural decomposition methods to the obtained high-quality Keck spectra and high-resolution HST images, black hole masses ($M_{BH}$ ) are estimated from the Hbeta broad emission line with the 5100A nuclear luminosity, and bulge luminosities ($L_{bul}$ ) are derived from the surface photometry. Based on these consistent measurements, we constrain the redshift evolution of the$M_{BH}-L_{bul}$ relation by performing the Monte Carlo simulations designed to account for selection effects. We provide implications of our results in terms of the black hole-galaxy co-evolution and discuss possible bulge growth mechanisms. -
We report the preliminary results of our GMVA(Global mm VLBI Array) observation at the frequency of 86 GHz. Observation were made in the dual polarization mode (LCP and RCP), to produce the polarimetric maps with the maximum angular resolution which the array is capable of. We aim to link the source-integrated AGN polarization properties with the polarized spatial source structure, by mapping the polarized "fine structure" of the target AGN. We selected 2 targets, 0954+658 and 0716+714, which (1) have been observed multiple times by the PdBI polarimetric monitoring program; (2) have sufficient integrated fluxes (
$S_{90GHz}$ > 1 Jy) ; (3) are close enough to resolve the source structure < 1 pc with given angular resolution ; and (4) are located at high northern declination for good UV coverages. As preliminary results, we present LL and RR polarized images of each target with the maximum angular resolution of${\sim}60{\mu}as$ . Extended structures, probably the jet outflows, are discovered in both sources. -
AGN are known for irregular variability on all time scales, down to intra-day variability with relative variations of a few percent within minutes to hours. In the shortest time scale of AGN activity, unexplored territory still exists: first, the existence of a shortest time scale of AGN activity and secondly the shape of high frequency end of AGN power spectrum. Also the spectral variations at the shortest timescale. Here, we present the preliminary results of AGN fast photometry performed with Korean VLBI Network(KVN). Observations were done in a 'anti-correlated' mode using two antennas, with always either one antenna pointing at the target. This results in an effective time resolution of 3 minutes. We used all four KVN frequencies, 22, 43, 86, and 129 GHz, in order to trace spectral variability. We have been able to derive high-quality light curves for 3C111 and 3C279 at 22 and 86 GHz observed on 31st of May and 30th of Nov. in 2012. We are currently performing detailed statistical analysis in order to assess the levels of variability or the corresponding upper limits.
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We investigate the origin of radio emission in nearby early-type galaxies using the European VLBI Network (EVN) at 1.4 GHz. The sample included NGC 1277, which was found to have an over-massive black hole of
$1.7{\times}10^{10}M_{\odot}$ , and four other early-type galaxies in the Perseus cluster. All the sources were detected above$5{\sigma}$ . They show compact radio cores and high brightness temperatures,$10^7{\sim}10^9K$ , which implies that radio emission in these objects is non-thermal. While the observed radio luminosities could be consistent with star formation (${\sim}1M_{\odot}yr^{-1}$ ), the small source size would imply a specific star formation rate (sSFR) of${\sim}10^6M_{\odot}yr^{-1}kpc^{-2}$ . Such a high sSFR rules out ongoing star formation. Supernovae (SNe) are ruled out as well because it is unlikely that we see SNe in all galaxies at the same time, and there is no significant radio variability either. The most plausible scenario is that these galaxies show low luminosity AGN activity in the radio, although there is no sign of AGN activity in other bands. If our interpretation is correct, then regular early-type galaxies may harbor active AGN more often than suspected from observations at other wavelengths. -
The local environmental effects on the active galactic nucleus(AGN) activity has been studied by many authors, but there is still controversy. We performed statistical analysis for nearby(0.01 < z < 0.05) volume limited(Mr < -19) sample via visual inspection based on Sloan Digital Sky Survey Data Release7. We visually inspect around 50,000 galaxy images to find peculiar objects which show not only ongoing merging features and tidal features, but also post merging features like shell or ring structures. We found that the frequency of AGN host galaxies is at least 2 times higher among peculiar galaxies than non-peculiar galaxies, and this trend is still visible when galaxy properties such as color or stellar mass are fixed. Furthermore, L[OIII] of peculiar galaxies is found to be more increased than those of normal galaxies. The majority of the most luminous AGN hosts show peculiar feature, which indicates that the luminous AGN galaxies may be the result of the local environmental effects. In addition, the enhancement of L[OIII] in peculiar galaxies is more significant for bluer galaxies, which implies that AGN activity is enhanced effectively when gas is available. In order to ensure our results, we also checked it for a smaller subsample with 2 magnitude deeper monochromatic images provided by SDSS Stripe82 database, and found consistent results. Overall, the results of this study tell us that the local environment of galaxies affects the frequency as well as the strength of AGN activity.
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Type Ia supernovae (SNe Ia) are a powerful tool to investigate the expansion history of the universe, because their peak luminosity is as bright as a galaxy and is known as an excellent standard candle. Since the discovery of the acceleration of the universe based on the observations of SNe Ia, higher than ever accuracy of their peak luminosity is needed to investigate various problems in cosmology. We started a project to improve the accuracy of the calibration of the peak luminosity of SNe Ia by measuring accurate distances to nearby resolved galaxies that host SNe Ia. We derive accurate distances to the SN Ia host galaxies using the method to measure the luminosity of the tip of the red giant branch (TRGB). In this study we present the results for M66 and M96 in the Leo I Group which are nearby spiral galaxies hosting SN 1989B and SN 1998bu, respectively. We obtain VI photometry of resolved stars in these galaxies from F555W and F814W images in the Hubble Space Telescope archive. We derive the distances to these galaxies from the luminosity of the TRGB. With these results we derive absolute maximum magnitudes of two SNe (SN 1989B in M66 and SN 1998bu in M96). We derive a value of the Hubble constant from the optical magnitudes of these SNe Ia and SN 2011fe in M101 based on our TRGB analysis. This value is similar to the values derived from recent estimates from WMAP9 and Planck results, but smaller than other recent determinations based on Cepheid calibration for SNe Ia luminosity.
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We studied recent evolution of M31 and M33 with star-forming regions and hot massive stars. We use GALEX far-UV and near-UV imaging to detect the star-forming regions and trace the recent star formation across the entire disk of galaxies. The GALEX imaging, combining deep sensitivity and entire coverage of these galaxies, provides a complete picture of the recent star formation in M31 and M33, and its variation with environment throughout these galaxies. We also show results from recent extensive surveys in M31 and M33 with Hubble Space Telescope multi-wavelength data including UV filters, which imaged several regions at a linear resolution of less than half a pc in these galaxies. Both datasets allow us to study the hierarchical structure of star formation: the youngest stellar groups are the most compact, and are often arranged withing broader, sparser structures. The derived recent star-formation rates are rather similar for the two galaxies, when scaled for the respective areas.
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WIth high accretion rate and low black hole mass, narrow line seyfert 1 galaxies (NLS1s) are an interesting sub-class of AGNs. To investigate whether NLS1s follow the same M-
${\sigma}*$ relation as other AGNs, we selected a sample of 110 NLS1s at relatively low redshift z < 0.1 from SDSS DR7 by constraining the FWHM of Ha broad component, and determined their black hole masses. We measured stellar velocity dispersion of 65 objects which showed strong enough stellar lines in the SDSS spectra, while we adopted the${\sigma}*$ measurements of 45 objects from Xiao et al. 2011. We find that NLS1s follow the M-${\sigma}*$ relation of active and inactive galaxies while there is a dependency due to the galaxy inclination, which probably cause rotational broadening of stellar absorption lines. -
We utilize Sloan Digital Sky Survey DR7 spectroscopic data of ~380 star forming galaxies in the Virgo cluster to investigate their chemical properties depending on the environments. The chemical evolution of galaxies is linked to their star formation histories as well as to the gas interchange in different environments. We derived star formation rate (SFR) and gaseous metallicity (e.g., oxygen abundance) of star forming galaxies. Combining with GALEX ultraviolet photometry and ALFALFA HI 21 cm data, we examine the relations between SFRs, metallicity, and HI deficiency of galaxies in various regions of the Virgo cluster. We also quantify the degree of ram pressure around galaxy using the ROSAT X-ray surface brightness map. We discuss environmental effects on the chemical properties and evolution of star forming galaxies.
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Kim, Suk;Yi, Wonhyeong;Rey, Soo-Chang;Sung, Eon-Chang;Jerjen, Helmut;Lisker, Thorsten;Lee, Youngdae;Lee, Woong;Chung, Jiwon;Pak, Mina 47.1
We present structural parameters of galaxies in the Extended Viro Cluster Catalog (EVCC), new catalog of galaxies in the Viro cluster using homogeneous Sloan Digital Sky Survey (SDSS) Date Release 7 (DR7) data. The EVCC covers more extended region of the Viro cluster than of the Virgo Cluster Catalog (VCC) and presents updated morphologies of galaxies using multi-band images and spectral features. We obtain the surface brightness profiles of galaxies using ellipse task in IRAF. Based on the analysis of surface brightness profile we construct a catalog of various structural parameters of galaxies, i.e. central surface brightness, effective radius, sersic index, effective surface brightness, and mean effective surface brightness. Taking advantage of these structural parameters in various parameter spaces, we refine criteria of dividing giant elliptical and dwarf elliptical galaxies. In addition, we found that bulge dominated galaxies have larger sersic index and brighter central surface brightness than disk dominated galaxies. At fixed magnitude, dwarf elliptical galaxies dwarf lenticular galaxies, and dwarf irregular low surface brightness (LSB) galaxies show larger effective radii than giant elliptical galaxies, giant lenticular galaxies, and irregular high surface brightness (HSB) galaxies, respectively. Dwarf elliptical galaxies and dwarf irregular LSB galaxies occupy the similar structural parameter spaces. We suggest that giant elliptical galaxies and dwarf elliptical galaxies may have different origin. -
Kim, Suk;Rey, Soo-Chang;Sung, Eon-Chang;Jerjen, Helmut;Lisker, Thorsten;Lee, Youngdae;Chung, Jiwon;Yi, Wonhyeong;Park, Mina 47.2
We present ultraviolet (UV) color-magnitude relations (CMRs) of early-type dwarf galaxies in the Viro cluster, combining Galaxy Evolution Explorer (GALEX) UV data with SDSS optical data, based on the Extended Virgo Cluster catalog (EVCC). We find that dwarf lenticular galaxies (dS0s) show a surprisingly distinct and tight locus separated from that of ordinary dEs, which is not clearly seen in previous CMRs. The dS0s in UV CMRs follow a steeper sequence than dEs and show bluer UV-optical color at a given magnitude. We explore the observed CMRs with population models of a luminosity-dependent delayed exponential star formation history. The observed CMR of dS0s is well matched by models with relatively long delayed star formation. The dS0s are most likely transitional objects at the stage of subsequent transformation of late-type progenitors to ordinary red dEs in the cluster environment. Most early type dwarf galaxies with blue UV colors (FUV-r < 6 and NUV-r < 4) are identified as those showing spectroscopic hints of recent or ongoing star formation activities. In any case UV photometry provides a powerful teel to disentangle the diverse subpopulations of early-type dwarf galaxies and uncover their evolutionary histories. lenticular galaxies, and irregular high surface brightness (HSB) galaxies, respectively. Dwarf elliptical galaxies and dwarf irregular LSB galaxies occupy the similar structural parameter spaces. We suggest that giant elliptical galaxies and dwarf elliptical galaxies may have different origin. -
We present galaxy luminosity functions (LFs) of subgroups in the Ursa Major cluster. The membership of galaxies is determined by radial velocities which are compiled from the SDSS and NED. We found that the faint end slope (
${\alpha}$ ) of the LF of all sample galaxies in Ursa Major is${\alpha}=-1.13$ . This is consistent with previous result, but shallower than that of the Virgo cluster. Interestingly, the subgroups in Ursa Major show different slopes in their LFs. The NGC 3992 and NGC 4111, the massive subgroups in the Ursa Major cluster, exhibit steep slopes of their LFs comparable to that of the Virgo cluster. On the other hand, less massive group (NGC 3877) shows a very shallow slope of -0.84. Based on the results, we discuss the evolution of galaxies and the assembly history of the Ursa Major cluster. -
To understand the connection between active galactic nuclei (AGNs) and star formation, we investigated the relation between AGN bolometric and far-infrared (FIR) luminosities, using type-2 AGNs. By matching type-2 AGNs at z < 0.3 selected from the SDSS based on the emission-line diagnostics, against the AKARI/FIS All-Sky Survey Catalogue and the COSMOS PEP (PACS Evolutionary Probe) Survey Catalogue, we obtained a sample of 729 type-2 AGNs detected in the AKARI survey (
$90{\mu}m$ ) and 17 ones detected in the PEP survey ($100{\mu}m$ ). For AGN bolometric luminosities, we adopted an estimate based on the [OIII] and [OI] line luminosities. We confirmed that there is a correlation between the AGN bolometric and FIR luminosities with a large scatter, which is consistent with previous studies. However, we claim that this correlation suffers from various artificial effects, e.g., FIR detection limits, survey volumes, and so on. We will discuss the limitations of studying the connection between AGN and star formation using currently available facilities. -
We present a new galaxy classification scheme in the Wide-field Infrared Survey Explorer (WISE) [
$3.4{\mu}m$ ]-[$12{\mu}m$ ] color versus$12{\mu}m$ luminosity diagram. In this diagram, galaxies can be classified into three groups in different evolutionary stages. Late-type galaxies are distributed linearly along "MIR star-forming sequence" identified by Hwang et al. (2012). Some early-type galaxies show another sequence at [3.4]-[12]$(AB){\simeq}-2.0$ , and we call this 'MIR blue sequence'. They are quiescent systems with old stellar population older than 10 Gyr. Between the MIR star-forming sequence and the MIR blue sequence, some early- and late-type galaxies are sparsely distributed, and we call these galaxies 'MIR green cloud galaxies'. Interestingly, both MIR blue sequence galaxies and MIR green cloud ones lie on the red sequence in the optical color-magnitude diagram. However, MIR green cloud galaxies have lower stellar masses and younger stellar populations (smaller$D_n4000$ ) than MIR blue sequence galaxies, suggesting that MIR green cloud galaxies are in the transition stage from MIR star-forming sequence galaxies to MIR blue sequence ones. We present differences in various galaxy properties between the three MIR classes using a multi-wavelength data, combined with the WISE and Sloan Digital Sky Survey Data Release 10, of local (0.03 < z < 0.07) galaxies. -
We report preliminary results from a radio study of central galaxies in cool and non-cool core clusters. A cooling flow is expected to rapidly form in the center of galaxy clusters unless additional heating mechanisms such as merging with sub clusters are at work. It has been suggested that cool flows can feed the AGN in the central galaxies, increasing their power. On the other hand, the AGN feedback can also affect the surrounding medium, heating back up the gas in the cluster core region. In this study, we investigate the co-evolution of cool flows and the AGN of galaxies located in the cluster center. For this study, we have selected 13 radio bright central galaxies from clusters with a range of cooling time scale. In this work, we present results of our recent observations using the Korean VLBI Network. We discuss the properties of the sample in radio and other wavelengths.
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Blue Compact Dwarf galaxies (BCDs) are systems which have been experiencing the bursts of star formation in their central region. As one of the origins of active star formation, tidal interaction (merger or fly-by between dwarf galaxies) has been suggested. A pair of BCDs, ESO 435-IG20 and ESO 435-IG16, are suspected to be a good example of such case. They are located at a similar redshift and separated only by ~130 kpc at their distances. In addition a bridge-like HI structure has been found between these two BCDs in the HIPASS survey. In this study, using the ATCA HI data of a much better resolution, we probe the gas morphology and kinematics of individual galaxies. We discuss how tidal interaction is responsible for the high star formation rate in this BCD pair.
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Galaxy clusters, the largest gravitationally bound systems, are an important means to place constraints on cosmological models. Moreover, they are excellent places to test galaxy evolution models in connection to the environments. To this day, massive clusters have been found unexpectedly at high redshfit (Kang & Im 2009, Durret et al. 2011, Tashikawa et al. 2012), and evolution of galaxies in cluster has not been fully understood. Finding galaxy cluster candidates at z > 1 in wide, deep imaging survey data will enable us to solve such issues of modern extragalactic astronomy. We report new candidates of galaxy clusters in the wide and deep survey fields, European Large Area ISO Survey North1(ELAIS-N1) and North2(ELAIS-N2) fields, covering sky area of
$8.75deg^2$ and$4.85deg^2$ each. We also suggest a new useful colour-colour selection technique to separate 1 < z < 2 galaxies from low-z galaxies by combining multi-wavelength data from the UKIRT Infrared Deep Sky Survey Deep Extragalactic Survey (UKIDSS DXS, JK bands), Spitzer Wise-area InfraRed Extragalactic survey (SWIRE, Optical-Infrared bands), Canada France Hawaii Telescope (CFHT, z band) and Infrared Medium-deep Survey(IMS, J band). -
Submillimeter galaxies are the progenitors of massive galaxy formation, and therefore their interaction with the early intergalactic medium must be an important subject in the cosmology and galaxy astrophysics. However, their detailed relation between the galaxies and surrounding environments is still largely unknown. In this poster, we will present the characteristics of their surrounding environments of a large sample of mm-detected submillimeter galaxies. We will also discuss the proposal for the future observations of these galaxies and their environments using the ALMA and the GMT.
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Galactic fly-by interactions are believed to be far more frequent than direct mergers, acting as hidden drivers of galaxy evolution. We perform a tree-particle-mesh code GOTPM, and investigate the statistical properties of the fly-by interactions as functions of halo masses and ambient environments. Based on the total energy of the two halos of interest, impulsive fly-by pairs are identified from eventual merger candidates. We find three obvious results as follows: (1) Halos in the high-dense environment experience more frequent mergers and fly-by encounters than those in the low-dense region; (2) In the massive halos, both merger and fly-by fractions evolve more dramatically with time than those in dwarfs; and (3) The fly-by fraction decreases as approaching the present epoch, in contrast to the increase of the merger fraction.
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We present new analyses of FLS 1718+59, a galaxy-galaxy gravitational lens system in the Spitzer First Look Survey (FLS) Field. A background galaxy (z = 0.245) is severely distorted by a nearby elliptical galaxy (z = 0.08), which can be interpreted as a result of gravitational lensing. We analyze this system by multiple methods, including ELLIPSE fitting, gravitational lens modeling, and surface brightness fitting. From this analysis, we obtain parameters of the lens galaxy using varying approaches and compare them. In the future, we will conduct SED fitting for the lens galaxy and estimate the stellar mass, and compare this with the total mass of the lens to check the M-L relation.
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We explore the relative importance of the role of small-scale environment and large-scale environment in triggering nuclear activity of the local galaxies using a volume-limited sample with
$M_r$ < -19.5 and 0.02 < z < 0.0685 selected from the Sloan Digital Sky Survey Data Release 7. The active galactic nuclei (AGN) host sample is composed of Type II AGNs identified with flux ratios of narrow emission lines with S/N > 6 and the central velocity dispersion of the sample galaxies is limited to have a narrow range between 130 <${\sigma}$ < 200($km\;s^{-1}$ ), corresponding to 7.4 <$log(M_{BH}/M_{\odot})$ < 8.1 in order to fix the mass of the supermassive black hole at the center of its host galaxy. In this study, we find that the AGN fraction ($f_{AGN}$ ) of late-type galaxies are larger than of early-type galaxies and that for target galaxy with late-type nearest neighbor,$f_{AGN}$ starts to increase as the target galaxy approaches the virial radius of the nearest neighbor (about a few hundred kpc scale). The latter result may support the idea that the hydrodynamic interaction with the nearest neighbor as well as tidal interaction and merger also plays an important role in triggering the nuclear activity of galaxy. We also find that early-type cluster galaxies show decline of AGN activity compared to ones in lower density regions, whereas the direction of dependence of AGN activity for late-type galaxies is opposite. -
Kim, Jaeyeong;Jeong, Woong-Seob;Pak, Soojong;Sim, Chae Kyung;Park, Won-Kee;Pavel, Michael D. 53.1
We compiled a near-infrared photometric and polarimetric catalog of$5{\times}9$ fields (${\sim}39^{\prime}{\times}69^{\prime}$ ) in the eastern side of the Large Magellanic Cloud (LMC). This catalog contains 9067 sources brighter than 16 mag in the J, H, and Ks bands, the polarization degree and position angle of each source. The photometric and polarimetric data were simultaneously obtained in J, H, and Ks bands using SIRPOL, an imaging polarimeter of the InfraRed Survey Facility (IRSF), in 2008 December and 2011 December. In this poster, we present a comparison between our results and those of Nakajima et al. (2007, PASJ, 59, 519) on the same sources in the 30 Doradus region in the LMC. We also discuss possible uncertainties in our polarimetric results when the Source Extractor is used to measure aperture photometry. -
외부 고리를 갖는 은하들(Outer ring galaxies)을 SDSS dr7 목록에서 분류하여, 이들이 갖는 특징과 링 구조(Ring structure)를 형성하는데 외부환경의 요인이 있는지 조사하고자 했다. z<0.05, b/a>0.6, R>6"의 조건에서 25,308개의 은하들을 추출하였고, SDSS image tool을 이용하여 531개의 외부 고리 은하(Outer ring galaxies)또는 외부고리를 갖고 있는 것처럼 보이는 은하(Ring-like galaxies)를 육안으로 분류하였다. 5개(u, g, r, i, z)의 필터로 관측되어진 CCD 이미지의 분석으로 최종적으로 69개의 외부고리 은하(Outer ring galaxies)를 선정하였다. 통계적으로 전체 은하에서 외부 고리 은하가 차지하는 비율이 약 0.2726%라는 결과를 얻게 되었고, 은하들의 주변의 환경을 조사한 결과 배경밀도와 비리얼 반경에 있어서 다른 형태의 고리를 갖고 있는 은하들과의 유의미한 특이점은 보이지 않았다.
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Lee, Hye-Ran;Lee, Joon Hyeop;Kim, Minjin;Oh, Seulhee;Ree, Chang Hee;Jeong, Hyunjin;Kyeong, Jaemann;Kim, Sang Chul;Lee, Jong Chul;Ko, Jongwan;Park, Byeong-Gon;Sheen, Yun-Kyeong 55.1
The properties of bright galaxies are closely related to those neighbors and satellite galaxies. However, the effects of nearby companion are known to be very weak in a galaxy cluster, when the companions are bright galaxies. On the other hand, until now, it has not been clear whether the properties of bright galaxies are affected by their faint satellites in a galaxy cluster. Recently, J. H. Lee et al. (in preparation) have found that the colors of bright galaxies in WHL J085910.0+294957, a galaxy cluster at z = 0.3, show a measurable correlation with the mean colors of faint galaxies around them. To confirm that result and to investigate the host-satellite relationship depending on cluster properties, we carry out follow-up studies of a few galaxy clusters, beginning with Abell 3659 (z ~ 0.0907) imaged in the g' and r' bands using IMACS on the Magellan (Baade) 6.5m telescope. Cluster members are selected based on the distributions of color, size and concentration along magnitude and spatial distribution. In this poster, we present some preliminary results: marginal correlations in color between bright galaxies and their faint companions are found at the central region of Abell 3659. The implication of these results is discussed. -
We examine the effect of environment on star formation activity of a sample of a galaxy group catalogue constructed from the Sloan Digital Sky Survey(SDSS DR8) given in Tempel et al.(2012). As an environmental parameter, we use the richness of the galaxy group. According to this parameter, we select 6846 galaxies in dense environment and 297335 galaxies in low environment. By comparing the two samples, we identify the different relationship between star formation rate and stellar mass. In order to compare galaxies in different environment, we fixed other parameters(color, apparent magnitude), which can affect star formation efficiency except for stellar mass. Also, based on HI mass from the ALFALFA survey, we study the environmental dependence of Kennicutt-Schmidt law which show the correlation between star formation rate and gas content.
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Supernovae type Ia (SNe Ia) cosmology is providing the only direct evidence for the presence of dark energy. This result is based on the assumption that the look-back time evolution of SNe Ia luminosity, after light-curve shape correction, would be negligible. However, the most recent compilation of SNe Ia data shows systematic difference in the Hubble residual (HR) between the E and Sd/Irr galaxies, indicating that the light-curve fitters used by the SNe Ia community cannot quite correct for a large portion of the population age effect. In order to investigate this possibility more directly, we have obtained low-resolution spectra for 30 nearby early-type host galaxies. This data set is used to estimate the luminosity-weighted mean ages and metallicities of host galaxies by employing the population synthesis models. We found an interesting trend between the host galaxy age and HR, in the sense that younger galaxies have positive residuals (i.e., light-curve corrected SNe Ia luminosity is fainter). This result is rather independent of the choice of the population synthesis models employed. Taken at face value, this age (evolution) effect can mimic a large fraction of the HR used in the discovery of the dark energy. This result is significant at 1.4 - 3 sigma levels, depending on the light curve fitters adopted, and further observations and analyses are certainly required to confirm the trend reported here.
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We study the three-dimensional genus topology of large-scale structure using the CMASS Data Release 11 sample of the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). The CMASS sample yields a genus curve that is characteristic of one produced by Gaussian random-phase initial conditions. The data thus supports the standard model of inflation where random quantum fluctuations in the early universe produced Gaussian random-phase initial conditions. Modest deviations in the observed genus from random phase are as expected from the nonlinear evolution of structure. We construct mock SDSS CMASS surveys along the past light cone from the Horizon Run 3 (HR3) N-body simulations, where gravitationally bound dark matter subhalos are identified as the sites of galaxy formation. We study the genus topology of the HR3 mock surveys with the same geometry and sampling density as the observational sample, and the observed genus topology to be consistent with LCDM as simulated by the HR3 mock samples.
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We investigate the method to measure both the present value of the matter energy density contrast and the Hubble parameter directly from the measurement of the linear growth rate which is obtained from the large scale structure of the Universe. From this method, one can obtain the value of the nuisance cosmological parameter $\Omo$ (the present value of the matter energy density contrast) within 3% error if the growth rate measurement can be reached $z >3.5$. One can also investigate the evolution of the Hubble parameter without any prior on the value of $H_0$ (the current value of the Hubble parameter). Especially, estimating the Hubble parameter are insensitive to the errors on the measurement of the normalized growth rate $f \sigma_8$. However, this method requires the high $z$ ($z >3.5$) measurement of the growth rate in order to get the less than 5% errors on the measurements of $H(z)$ at $z \leq 1.2$ with the redshift bin $\Delta z = 0.2$. Thus, this will be suitable for the next generation large scale structure galaxy surveys like WFMOS and LSST.
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Cosmology is entering an era of percent precision with large surveys, demanding accurate simulations. In this paper, we aim to study the effects of initial conditions on the results of cosmological simulations, which will help us to make percent-level accuracy simulations. For this purpose, we use a series of cosmological N-body simulations with varying initial conditions. We test the influence of the initial conditions, namely the pre-initial configuration (preIC), the order of the perturbation theory, and the initial redshift, on the statistics associated with the large scale structures of the universe such as the halo mass function, the density power spectrum, and the maximal extent of the large scale structures. We find that glass or grid pre-initial conditions give similar results. However, the order of the Lagrangian perturbation theory used to generate the initial conditions and the starting epoch of the simulations play a crucial role, especially at high redshift (z ~ 2-4). The initial conditions have to be chosen with care, taking into account the specificity of the simulation.
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The main idea of the Alcock-Paczynski (AP) test is that, if we use a wrong distance-redshift relation to infer the shape of a spherical object in the Universe, this object may look non-spherical. To probe the cosmic expansion history through the AP test, the key point is to find something which is known as spherical in the Universe. We propose two possible ways applying the AP test to the large scale structure (LSS): 1) Based on the observed galaxies or quasars, one built up the beta-skeleton tracing the LSS, and investigating the inhomogeneity of the connections; 2) One reconstructs the smoothed density-contrast gradient field based on LSS observations, and investigating the inhomogeneity of the gradient vectors. Compared with some existed methods probing AP effect through 2-point correlation function, galaxy pairs, or voids, our methods have various advantages: 1) The information of both the high and low dense regions of the LSS are taken into account. 2) The redshift space distortion as the main contamination to the AP effect can be easily removed.
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Both peculiar velocities and errors in the assumed redshift-distance relation ("Alcock-Paczynski effect") generate correlations between clustering amplitude and orientation with respect to the line-of-sight. In this talk we propose a novel technique to extract the Alcock-Paczynski, geometric, distortion information from the anisotropic clustering of galaxies in 3-dimensional redshift space while minimizing non-linear clustering and peculiar velocity effects. We capitalize on the recent, large dataset from the Sloan Digital Sky Survey III (SDSS-III), which provides a large comoving sample of the universe out to high redshift. We focus our analysis on the Baryon Oscillation Spectroscopic Survey (BOSS) constant mass (CMASS) sample of 549,005 bright galaxies in the redshift range 0.43Type Ia supernovae (SNe) are providing the most conclusive evidence for accelerating universe with dark energy in observational cosmology. In these investigations, look-back time evolution of SNe luminosity is regarded as negligible on the basic assumption. However, several recent works present some systematic differences among hosts which have different characteristics of stellar population. For more direct investigation, we are proceeding with our YONSEI (YOnsei Nearby Supernovae Evolution Investigation) project. Only early-type hosts in our catalogue were chosen in order to estimate the luminosity-weighted mean age and metallicity directly using Single Stellar Population (SSP) models and ignore the effect from the dust extinction. Observations using low-resolution spectrographs are still in progress at Las Campanas Observatory with 2.5m telescope and at McDonald Observatory with 2.7m telescope. We have thus far obtained spectra for 30 early-type hosts. After weak emission line correction, Lick/IDS absorption-line indices are measured and YEPS spectroscopic evolution model was applied to determine mean population ages and metallicities. Our preliminary results show that SNe Ia hosted in older galaxies seem to be brighter at 1.4 - 3 sigma levels, however, more observations and analyses are still needed to confirm this correlation.The luminosity evolution of Type Ia supernova (SN Ia) and dust extinction play major roles in the systematic uncertainties in the SN cosmology. In order to overcome these obstacles, here we propose to use GMT-GMACS to take spectra for early-type host-galaxies of SNe Ia in the redshift range between 0.2 and 1.0. This high-redshift sample will be taken from Dark Energy Survey (DES), which expects more than 200 early-type hosts at this redshift range. They will be compared with nearby early-type hosts, for which we are now obtaining low-resolution spectra. We will select host-galaxies of same population age range for both nearby and high-redshift samples to reduce the possible evolution effect. Since we are dealing with early-type galaxies, our test is also less affected by dust extinction. We expect that our evolution-free and dust-free dark energy test will provide more robust results on the nature of dark energy.We study tidal disruption and subsequent mass fallback process for stars approaching supermassive black holes on bound orbits, by performing three dimensional Smoothed Particle Hydrodynamics simulations with a pseudo-Newtonian potential. We find that the mass fallback rate decays with the expected -5/3 power of time for parabolic orbits, albeit with a slight deviation due to the self-gravity of the stellar debris. For eccentric orbits, however, there is a critical value of the orbital eccentricity, significantly below which all of the stellar debris is bound to the supermassive black hole. All the mass therefore falls back to the supermassive black hole in a much shorter time than in the standard, parabolic case. The resultant mass fallback rate considerably exceeds the Eddington accretion rate and substantially differs from the -5/3 power of time. We also show that general relativistic precession is crucial for accretion disk formation via circularization of stellar debris from stars on moderately eccentric orbits.Electron magnetohydrodynamic (EMHD) turbulence provides a fluid-like description of small-scale magnetized plasmas. Most EMHD turbulence studies consider "balanced" EMHD turbulence. However, imbalanced EMHD turbulence has never been studied. In this study, we numerically study "imbalanced" EMHD turbulence. Imbalanced turbulence means that wave packets moving in one direction have high amplitudes or strong perturbations than the others. In driven imbalanced EMHD turbulence, non-zero magnetic helicity is injected. When magnetic helicity is injected at a scale, we expect to have inverse cascade of magnetic helicity, as well as magnetic energy, in three-dimensional (3D) EMHD turbulence. For no helicity injection, we do not observe inverse energy cascade. However, when magnetic helicity is injected, inverse cascade of magnetic helicity is clearly observed. Magnetic energy also shows inverse cascade. In EMHD turbulence, it is well known that magnetic energy on scales smaller than the energy injection scale is forward-cascading quantity and the magnetic energy spectrum follows a k^{-7/3} one. On the other hand, the inverse-cascading entity on scales larger than the energy injection scale is uncertain. If the magnetic helicity is inverse-cascading quantity, we will obtain a k^{-5/3} magnetic energy spectrum. In our simulations, we do observe energy spectrum consistant with k^{-5/3} on large scales. Therefore, we confirm that magnetic helicity indeed is the inverse-cascading entity in 3D EMHD turbulence.Turbulence is a common phenomenon in astrophysical fluids such as the interstellar medium (ISM) and the intracluster medium (ICM). In turbulence studies it is customary to assume that fluid powered by an energy injection on a single scale. However, in astrophysical fluids, there can be many different driving mechanisms that act on different scales simultaneously. In this work, we assume multiple energy injection scale (2
${\surd}$12 and 15 We present a study of optically emitting supernova remnants (SNRs) in M31 based on$H{\alpha}$ and [S II] images in the Local Group Survey. Using these images, we have selected objects that have [S II]:$H{\alpha}$ > 0.4 and morphology for typical SNRs. We find 76 new SNRs. We have also inspected 233 SNR candidates presented in previous studies, confirming that only 80 of them are SNRs. Combining these, we produce a master catalog of 156 SNRs in M31. We classify these SNRs according to two types of criteria: the SNR progenitor types (Type Ia and core-collapse (CC) SNRs) and the morphological types. Type Ia and CC SNRs are 23% and 77%, respectively, of the total sample. Most of CC SNRs are concentrated along the spiral arms, while Type Ia SNRs are rather spread over the entire galaxy including the inner region. CC SNRs are brighter in$H{\alpha}$ and [S II] than Type Ia SNRs. The cumulative size distribution of the SNRs with 15 < D < 50 pc is well fitted by a power law with an index,${\alpha}=2.53{\pm}04$ . It indicates that most SNRs in M31 are in Sedov-Taylor phase. Properties of these SNRs show little variation depending on the galactocentric distance. The$H{\alpha}$ and [S II] surface brightness shows a good correlation with X-ray luminosity for the SNRs that are center-bright.We present the Exposure Time Calculator of IGRINS (Immersion Grating Infrared Spectrograph). The noises of IGRINS and the simulated emission line can be calculated from the combination of Telluric background emission and absorptions, the emission and transmission of the telescope and instrument optics, and the dark noise and the read noise of the infrared arrays. For the atmospheric transmissions, we apply the simulated spectra depending on the Precipitable Water Vapor (PWV) values. In case of calculation of noises, the user needs to input the expected target magnitude, the weather conditions, and the desired exposure time. In addition to the simulated emission line, the parameters of rest wavelength, line-flux, Doppler shift and line-width are needed. The output would be the expected signal-to-noise for each spectral resolution element. The source-code of IGRINS-ETC v2.1.1 is available to be downloaded on the World Wide Web.Recent spectroscopic observations have provided evidence for complex chemical evolution by supernovae and/or asymptotic giant branch (AGB) stars in the two metal-poor globular clusters (GCs) NGC2419 and M15. In particular, the horizontal branches (HBs) of these metal-poor GCs are very extended in the Hertzsprung-Russell diagram. The origin of these peculiar features, as well as that for the Sandage period-shift effect observed in these clusters, are yet to be understood. Here we show, by constructing population models including the Nitrogen enhanced subpopulation, that the second generation populations in these clusters would be enhanced not only in Helium, but also in Nitrogen. This working hypothesis can simultaneously explain the observed extended feature on the HB and the period-shift of RR Lyrae variables.Time Monitoring of SiO and$H_2O$ Masers Toward Orion KL: The Third Flaring of$H_2O$ Maser EmissionWe present the results of time monitoring observations of$^{28}SiO$ v = 1, 2, J = 1-0,$^{29}SiO$ v = 0, J = 1-0 and$H_2O$ $6_{16}-5_{23}$ maser lines toward radio Source I in Orion KL. The observations have been performed from 2009 June to 2013 April using the 21m single dish radio telescopes of the Korean VLBI Network. Both SiO and$H_2O$ maser lines were simultaneously obtained at 20 epochs. In particular, the third outburst of$H_2O$ maser emission (the first: 1985, the second: 1998) was detected and the flux density variation curve was obtained. The maximum flux density flared up to an order of$10^5$ Jy during 2012 May-July at peak velocity of 7.33 km$s^{-1}$ . Hirota et al. (2011) reported that the bursting maser features are located at 8" from Source I and coincident with the interacting region between the outflow from Source I and a dense ambient gas, Orion Compact Ridge. In the case of SiO masers arising from close to the Source I, the peak emission of the v = 1, J = 1-0 maser line appeared in 2010 April. We are investigating the possible relation between this SiO maser peak emission and the third$H_2O$ maser flaring.Unlike the conventional wisdom, observations made during the past decade have revealed that many globular clusters possess more than one stellar population. Here, we have discovered evidence for multiple red giant branches (RGBs) in the globular cluster NGC 6388 from the narrow-band Calcium and Str$\ddot{o}$ mgren b & y (Caby) photometry. In order to confirm the difference in Calcium abundance, we have acquired the low resolution spectroscopy for these RGB stars. In this paper, we will present results of our photometry and hand in the preliminary results of spectroscopic observations.High energy photons and mechanical energy produced by the process of star formation result in copious FIR molecular and atomic lines, which are important coolants of the system. Photons thermally or mechanically induced could dissociate water in the dense envelope to change relative abundances among the species O, OH, and H2O. Here we analyze OH emission lines toward embedded young stellar objects (YSOs) observed as part of the Herschel open time key program, 'Dust, Ice, and Gas In Time (DIGIT)' in order to study the physical conditions of associated gas and the energy budget loaded on the OH line emission. According to our analysis of the Herschel/PACS spectra, OH emission peaks at the central spaxel in most of sources, but several sources show spatially extended emission structures. In the extended emission sources, the distribution of OH emission is correlated with that of [OI] emission and extended along the outflow directions. Considering the diversity of source properties, ratios between detected OH lines are relatively constant among sources. In addition, each OH line has strong correlation with bolometric luminosity. For detail analyses with rotation diagram and non-LTE LVG model, we present the results from GSS30-IRS1 and Elias29.As more spectroscopic observations accumulate, it becomes evident that there are variations in light elements, such as C, N, O, and Na, between the sub-populations in most globular clusters (GC) in the Milky Way. We have constructed a new set of isochrones and horizontal branch evolutionary tracks with enhanced Nitrogen and depleted Oxygen to study their effects on the evolution of stars in GCs. From these results, we found that their effects on the evolution in color-magnitude diagram are significant in determining the age of GCs. In order to reflect these effects in the construction of population models for GCs, we have expanded the parameter space of Yonsei-Yale Isochrones and HB evolutionary tracks by introducing abundance enhancements of N for various global metal abundances and helium contents. In this paper, we will present our preliminary results from these calculations.Our understanding of how brown dwarfs form is limited by observational evidence. We report identification of a L328-IRS as a proto-brown dwarf embedded in an isolated dense molecular core. This source exhibits typical properties of a protostar, however, its luminosity (~0.05$L{\odot}$ ) is far below than expected from the least massive protostar by the standard star formation theory. The most likely mass accretion rate (~2.4 10-7$M{\odot}$ yr-1) inferred from its small bipolar outflow is an order of magnitude less than the canonical value for a protostar. The mass available in its envelope is less than 0.1$M{\odot}$ . These points suggest that L328-IRS will accrete the mass of a brown dwarf, but not that of a star. L328 is found to be fairly well isolated from other nearby clouds and seems to be forming three sub-cores simultaneously through a gravitational fragmentation process. Altogether with these, our direct detection of inward motions in L328 which harbors this proto-brown dwarf clearly supports the idea that a brown dwarf forms like a normal star.We present a study of outflows on 24 embedded young stellar objects (YSOs), which are selected from the sources of the Dust, Ice, and Gas in Time (DIGIT) Herschel key program. Molecular outflow activity, which is believed to have strong dependence on accretion process, is the most powerful in the early embedded phase of star formation and declines as the central protostars evolve to the main sequence stage. In order to study the relation between the CO outflow observed in low J transitions and the properties of protostars, we mapped the CO outows of the selected targets in J = 1-0 and J = 2-1 lines with the 14-m TRAO telescope and the 6-m SRAO telescope, respectively. We estimate CO outflow momentum fluxes (Fco) and compare with bolometric luminosity, Lbol, bolometric temperature, Tbol, and the FIR molecular line luminosities of CO,$H_2O$ , OH and [O I], which were detected by the Herschel-PACS observations. We found that$Fco_{1-0}$ is greater than$Fco_{2-1}$ , and the mean ratio is about 2. L1455-IRS3 and IRAM04191 have high Fco in spite of low$L_{bol}$ . The well known correlation between Fco and$L_{bol}$ . is not very evident from all our samples. However, Fco and$L_{bol}$ . show a rather strong correlation if L1455-IRS3 and IRAM04191 are excluded. Fco shows little correlation with FIR line luminosities of individual species, while the total FIR line luminosity summed over CO,$H_2O$ , OH, and [OI] lines seems to have some correlation. In addition, we report 22 GHz$H_2O$ , and 44 GHz CH3OH maser line detections in four sources out of the 24 YSOs.We present various observational results toward a small group of Young Stellar Objects (YSOs), L1251C. Observations by Spitzer Space Telescope legacy program "From Molecular Cores to Planet Forming Disks" (c2d; Evans et al. 2003) revealed that there are three YSOs within ~15" in L1251C: IRS1 (Class I), IRS2 (Class II), and IRS3 (Class II). In order to understand the molecular environment around these YSOs, we carried out the KVN single-dish observations in$HCO^+$ J=1-0,$H^{13}CO^+$ J=1-0,$N_2H^+$ J=1-0 and HCN J=1-0.$^{12}CO$ J=1-0 was also mapped in L1251C with the TRAO 14m telescope. Integrated intensity maps of high density tracers such as$H^{13}CO^+$ J=1-0,$N_2H^+$ J=1-0 and HCN J=1-0 show similar emission distributions, whose peaks are off the positions of YSOs. A compact$HCO^+$ J=1-0 outflow and an extended$^{12}CO$ J=1-0 outflow were observed, but their outflow axes are not cosistent ($HCO^+$ : NW-SE,$^{12}CO$ : EW). However, the highest velocity component of the$^{12}CO$ J=1-0 outflow shows similar morphology to the$HCO^+$ J=1-0 outflow, and ~ 23 % of$^{12}CO$ outflow momentum flux is loaded onto this high velocity component. Furthermore, continuum emission has been observed at 350, 450, 850${\mu}m$ , and 1.3mm. With the KVN single dish, the 22 GHz$H_2O$ maser emission has been also monitored toward L1251C to find variations of the systemic velocity and intensity with time.As part of the DIGIT key program, we observed GSS30-IRS1, a Class I object located in Ophiuchus (d=125 pc), with Herschel-PACS. More than 70 lines were detected in 50-200 micron band including CO, OH, H2O, and [OI]. All lines, except for [OI], were detected only at the central spaxel of$9.4^{{\prime}{\prime}}{\times}9.4^{{\prime}{\prime}}$ while the [OI] emission is extended along the NE-SW direction. One interesting feature in GSS30-IRS1 is that the continuum is extended beyond PSF, unlike line emission. It suggests that the external heating is important in GSS30-IRS1. For detail analysis of line fluxes, we apply the non-LTE LVG model, RADEX as well as simple rotational diagrams. We also use the Monte Carlo radiative transfer package, RADMC-3D to understand the heating mechanism of dust grains around GSS30-IRS1. We will discuss about heating and cooling processes associated with GSS30-IRS1.It has been known that HCN is one of ubiquitous high-density gas tracer, and the abundance ratio between HCN and its Isomer, HNC sensitively depends on kinetic temperature in star-forming regions. Here we investigate the molecular abundance ratio toward three different evolutionary phases of massive star formation: Infrared Dark Clouds, High-mass Protostellar Objects and Ultracompact HII Regions. We obtained the abundances of HCN and HNC using optically thin H13CN and HN13C lines observed with the KVN single-dish telescopes and MAMBO 1.2mm and SCUBA$850{\mu}m$ continuum data. According to our results, the ratio of [HCN]/[HNC] increases statistically with the evolutionary stage, indicative of the effect of temperature. We also found a strong anti-correlation between the column density of molecular hydrogen and the HNC abundance.Part of mid-J CO emission detected by the Herschel/PACS observations of embedded young stellar objects (YSOs) has been attributed to the UV-heated outflow walls. We have applied our newly developed self-consistent models of Photon Dominated Region (PDR) and Non-LTE line Radiative transfer In general Grid (RIG) to the Herschel FIR CO observations. If the black body radiation of T = 15,000 K is used, the observed mid-J CO line fluxes can be produced in inner dense regions (n${\geq}$ 106 cm-3) with -4.5${\leq}$ log Gdust/n${\leq}$ -2.5, where gas temperatures are larger than 300 K and CO abundances are${\geq}$ 10-5, along the UV-heated outflow walls. The contribution of the UV heated outflow cavity wall in Class I seems to be larger than that in Class 0.Im, Myungshin;Pak, Soojong;Park, Won-Kee;Kim, Ji Hoon;Kim, Jae-Woo;Lee, Seong-Kook J.;Karouzos, Marios;Jeon, Yiseul;Choi, Changsu;Jun, Hyunsung;Kim, Dohyeong;Hong, Jueun;Kim, Duho;Hyun, Minhee;Yoon, Yongmin;Taak, Yoon Chan;Kim, Yongjung;Baek, Giseon;Jeong, Hyeonju;Lim, Juhee;Kim, Eunbin;Choi, Nahyun;Lee, Hye-In;Bae, K.M.;Chang, Seunghyuk 68.1
Infrared Medium-Deep Survey is a near-infrared imaging survey geared toward understanding the formation and the evolution of quasars and galaxies at high redshift, and studying transient and time-variable objects such as gamma-ray bursts, supernovae, and young stellar objects. The survey uses a multi-tier structure, with deep imaging survey of 100$deg^2$ using UKIRT to the depth of 23 AB mag, and a shallower imaging of interesting sources using the CQUEAN camera on the 2.1m telescope at McDonald observatory. This talk will give an overview of the survey strategy, the instrument development, and science highlights. The science highlights will include the discovery of high redshift quasars, high redshift galaxy clusters, GRBs, and other interesting sources. At the end of the talk, we will also present the future prospects of our study.Park, Won-Kee;Pak, Soojong;Im, Myungshin;Choi, Changsu;Jeon, Yiseul;Chang, Seunghyuk;Jeong, Hyeonju;Lim, Juhee;Kim, Eunbin;Choi, Nahyun;Lee, Hye-In;Kim, Sanghyuk;Jeong, Byeongjoon;Ji, Taegeun 68.2
Camera for QUasars in EArly uNiverse (CQUEAN) is an optical CCD camera system made by Center for Exploration of the Origin of the Universe (CEOU). CQUEAN is developed for follow-up observation of red sources such as high-redshift quasar candidates ($z{\geq}5$ ), gamma-ray bursts (GRB), brown dwarfs and young stellar objects. The CQUEAN is composed of a science camera with deep-depletion CCD chip which is sensitive at around$1{\mu}m$ , a set of custom-made wide-band filters for detection of quasar candidates at z~5, and a guide camera. A focal reducer was developed to secure$4.8^{\prime}{\times}4.8^{\prime}$ field of view, and an in-house user software for efficient data acquisition. CQUEAN was attached to 2.1m Otto Struve Telescope in McDonald Observatory, USA, in August 2010. About 1000 quasar candidates including 3 confirmed with follow-up spectroscopy, have been observed so far, and many high-z galaxy cluster candidates, GRBs and supernovae were also observed. And monitoring of HBC 722, a young stellar object, is under way since 2011. Further enhancement of CQUEAN including the introduction of narrow-band filters is planned.We describe a survey of quasars in the early universe beyond z=5, which is one of the main sciences of the Infrared Medium-deep Survey (IMS) performed by the Center for the Exploration of the Origin of the Universe (CEOU). We use multi-wavelength archival data such as SDSS, CFHTLS, UKIDSS, and SWIRE, which provide deep images over wide areas sufficient enough for searching high redshift quasars. In addition, we carried out a J-band imaging survey at the United Kingdom InfraRed Telescope (UKIRT) with a depth of ~23 AB and survey area of ~100$deg^2$ , which makes IMS the most suitable survey for finding high redshift quasars at z~7. Also for the quasar candidates at z~5.5, we are conducting observations with the Camera for QUasars in EArly uNiverse (CQUEAN), which are efficient for selecting robust quasar candidate samples in this redshift range. We used various color-color diagrams suitable to the specific redshift ranges, which can reduce the contaminating sources such as M/L/T dwarfs, low redshift galaxies, and instrumental defects. The high redshift quasars we are confirming can provide us with clues to the growth of super massive black holes since z~7. Also by expanding the quasar sample at 5A galaxy cluster is an important laboratory to study the large scale structure in the Universe and the galaxy evolution. In order to identify candidate galaxy clusters at z~1, we have used deep and wide optical-NIR datasets based on IMS, UKIDSS DXS and CFHTLS wide covering${\sim}20deg^2$ in the SA22 field. We measure the angular two-point correlation function of the candidate clusters and investigate the star formation activity of the member galaxies. Based on bias factor and halo mass function, candidate clusters have the average halo mass of >$10^{14}h^{-1}M_{\odot}$ . At z~1, the star formation rate of cluster galaxies is similar to that of field galaxies, which indicates the environmental quenching is not so significant at z~1 as the local Universe.We present long-term optical to NIR data of the tidal disruption object, Swift J1644+57. The data were obtained with CQUEAN, UKIRT WFCAM observations. We analyze the morphology of the host galaxy of this object and decompose the bulge component using high resolution HST WFC3 images. We conclude that the host galaxy is bulge dominant. We also estimate the multi-band fluxes of the host galaxy through the light curves based on the long-term observational data. We fit the SED models to the multi-band fluxes of the host galaxy and determine its stellar mass. Finally, we estimate the mass of the central super massive black hole which is thought to be the main role of the tidal disruption event. The estimated stellar mass and black hole mass are$10^{9.1}M_{\odot}$ ,$10^{6.8}M_{\odot}$ respectively. We compare our results to other results that have studied before.Baek, Giseon;Pak, Soojong;Green, Joel D.;Lee, Jeong-Eun;Bae, Kyoung Min;Jeon, Yiseul;Choi, Changsu;Im, Myungshin;Meschiari, Stefano 70.2
We present collections of optical photometry for a pre-main sequence star HBC 722. It showed large amplitude optical outburst (${\Delta}V=4.7$ mag) in 2010 and classified as a FU Orionis type object. We have been observing HBC 722 from 2011 April to 2013 May, using Camera for QUasars in EArly uNiverse (CQUEAN) attached to the 2.1 m Otto Struve telescope at the McDonald Observatory. Time-series monitoring data (minute-scale interval) were obtained in SDSS r, i and z bands to see short-scale behaviors as well as trace the long-term brightness changes after the eruption in 2010. Interestingly, it started to brighten from 2011 early summer and became brighter than the first outburst peak in our 2013 May observation. We expect that the recovering phase would result from re-increase of disk accretion rate, might attribute to distinctive short-scale color features. In this presentation, we report long- and short-timescale optical behaviors of HBC 722 in the post-outburst phase.Koo, Jae-Rim;Lee, Jae Woo;Lee, Byeong-Cheol;Kim, Seung-Lee;Lee, Chung-Uk;Hong, Kyeongsoo;Lee, Dong-Joo;Rey, Soo-Chang 71.1
Among quadruples or higher multiplicity stars, only a few binary systems have been discovered. They are important targets to understand the formation and evolution of multiple stellar systems because we can obtain accurate stellar parameters from photometric and spectroscopic studies. We present the observational results of this kind of rare object 1SWASP J093010.78+533859.5, for which the doubly eclipsing feature had been detected previously from the SuperWASP photometric archive. Individual PSF photometry for two objects with a separation of about 1.9 arcsec was performed for the first time in this study. Our time-series photometric data show that the brighter object A is an Algol-type detached eclipsing binary with an orbital period of 1.3 days and the fainter B is a W UMa-type contact eclipsing binary with a period of 0.23 days. Using the high-resolution optical spectra, we obtained well-defined radial velocity variations of the system A. Furthermore, stationary spectral lines were detected and should have originated from the other stellar component, which was confirmed by the third object contribution from the light curve analysis. No spectral feature of the system B was detected, probably due to its faintness. We obtained the binary parameters and the absolute dimensions from each light curve synthesis. The primary and secondary components of the system A have a spectral type of K1 and K5 main sequences, respectively. Two components of system B have nearly the same type of K3 main sequence. Light variations at out of eclipses were appeared in both systems, interpreting as the effect of stellar spots on these late spectral type stars. We estimated the distances to the systems A and B individually. They may have similar distances of about 70 pc and seem to be gravitationally bound with a separation of about 130 AU. In conclusion, we suggest that 1SWASP J093010.78+533859.5 is a quintuple stellar system with a hierarchical structure of a triple system A(ab)c and a binary system B(ab).The standard stellar models for HIP 20916 and HIP 101769 have been constructed to determine the properties of the binary system. Augmented with speckle data which is the magnitude difference between stars of the binary system, the previously determined parameters, such as [Fe/H], distance, total mass, and etc, are used to construct the standard stellar models. And the Green table is used to convert L and$T_{eff}$ into$M_v$ and color for comparison between models and observational data. We present the constructed stellar models of the system.Even though current microlensing follow-up observations focus on high-magnification events due to the high efficiency of planet detection, it is very difficult to do a confident detection of planets in high-magnification events with extremely weak central perturbations (i.e., the fractional deviation is${\delta}{\leq}0.02$ ). For the confident detection of planets in the extremely weak central perturbation events, it is needed both the high cadence monitoring and the high photometric accuracy. A next-generation ground-based observation project, KMTNet (Korea Microlensing Telescope Network), satisfies both the conditions. Here we investigate how well planets in high-magnification events with extremely weak central perturbations are detected by KMTNet. First, we determine the probability of occurrence of events with${\delta}{\leq}0.02$ . From this, we find that for${\leq}100M_E$ planets in the separation of$0.2AU{\leq}d{\leq}20AU$ , events with${\delta}{\leq}0.02$ occur with a frequency of more than 70%, in which d is the projected planet-star separation. Second, we estimate the efficiency of detecting planetary signals in the events with${\delta}{\leq}0.02$ via KMTNet. We find that for main-sequence and subgiant source stars,${\geq}1M_E$ planets can be detected more than 50% in a certain range that has the efficiency of${\geq}10%$ and changes with the planet mass.We present a UBVI and$H{\alpha}$ photometric study of the young open cluster NGC 1893 in the outer Galaxy as part of "Sejong Open cluster Survey (SOS)" project. Using the properties of early-type stars in the photometric diagrams 65 early-type members were selected. More than 120$H{\alpha}$ emission stars and candidates were found by$H{\alpha}$ photometry. Together with the published young stellar object catalogue and X-ray source list for this cluster, a total of 837 pre-main sequence (PMS) stars were identified in our photometric data. We obtained the mean reddening of < E(B-V) > =$0.56{\pm}0.08$ mag from the (U-B, B-V) diagram and confirmed the normal reddening law ($R_V=3.1$ ) toward NGC 1893 based on color excess ratios from optical to mid-infrared wavelengths. The zero-age main sequence fitting to the reddening-corrected color-magnitude diagrams gives a distance modulus of$V_0-M_V=12.8{\pm}0.1$ . The age of the cluster inferred from stellar evolution models is about 1-2 Myr. We also found the Salpeter/Kroupa type initial mass function for this cluster. Finally, the mass accretion rate of 80 PMS stars with UV excess emission was estimated for the stars with masses from$0.6M_{\odot}$ to$5M_{\odot}$ .It is believed that the current census of star clusters in the Milky Way is far from being complete, because of high extinction. Taking advantage of recent wide-field infrared surveys (the WISE as well as 2MASS, UKIDSS GPS, and VVV), we search for new star clusters in the central region of the Milky Way (720$deg^2$ -wide area at |1| <$30^{\circ}$ and |b| <$6^{\circ}$ ). We find 1840 candidates by visual inspection of the WISE images. The spatial distribution of these candidates show a strong concentration along the Milky Way, showing that most of them belong to the Milky Way. Among them, 26 are probably star clusters, considering their morphology, color-magnitude diagrams, and the degree of central concentration of stars. Eighteen of them appear to be very young in the embedded phase, and six of them are considered to be relatively old, showing a developed red giant branch. Implications of the primary results will be discussed.Lee, Young-Wook;Han, Sang-Il;Joo, Seok-Joo;Lim, Dongwook;Jang, Sohee;Na, Chongsam;Roh, Dong-Goo 73.2
In the current${\Lambda}CDM$ hierarchical merging paradigm, a galaxy like the Milky Way formed by numerous mergers of ancient subsystems. Most of the relics of these building blocks, however, are yet to be discovered or identified. Recent progress in the Milky Way globular cluster research is throwing new light on this perspective. The discoveries of multiple stellar populations having different heavy element abundances in some massive globular clusters are suggesting that they are most likely the remaining cores or relics of disrupted dwarf galaxies. In this talk, we will report our progress in the (1) narrow-band photometry, (2) low-resolution spectroscopy, and (3) population modeling for this growing group of peculiar globular clusters.We have performed new narrow-band calcium photometry for Milky Way globular clusters (GCs) and detected multiple red giant branches (RGBs) in some massive GCs. Our new calcium filter was designed to avoid the CN contamination below$3883{\AA}$ and to measure only Ca II H&K lines. The fact that we are detecting multiple RGBs from the new filter is suggesting that they are indeed different in calcium abundance, which can only be produced by supernovae (SNe). Therefore, the presence of the multiple RGBs for the peculiar GCs in the calcium photometry is best understood if the later generation of stars are enhanced in some SNe products. In this talk, we will present our progress in the calcium photometry for the peculiar GCs showing the multiple RGBs.Recent spectroscopic observations have provided evidences for the multiple stellar populations having different abundances in some massive globular clusters (GCs). In particular, some of these GCs show clear separations of red giant-branches (RGBs) in calcium narrow band photometry. In order to confirm the differences in heavy element abundances and radial velocities among multiple RGBs, we have performed the low-resolution spectroscopy for the RGB stars in these GCs. The spectral data were taken from the multi-object spectroscopic mode with WFCCD mounted on the du Pont 2.5m telescope in Las Campanas Observatory. In this talk, we will present our progress in the spectroscopic analysis of the RGB stars in these GCs.산개성단은 은하계 내에서 그 일생을 보내며 자체적인 역학적 진화를 한다. 또한, 거대 성간 분자운, 은하의 회전 그리고 은하의 중력 등에 영향을 받아 성단의 헤일로 영역에 조석꼬리와 같은 구조로 나타날 수 있다. 이러한 현상을 관측하기는 어려운데 그 이유는 넓은 영역에 걸쳐 있는 성단의 흐린 구성원에 대한 고유운동 자료가 없어 낱별과 성단의 구성원을 구별하는 것이 어렵기 때문이다. 우리는 이 문제를 통계적으로 해결하기 위하여 "4차원 구성원 확률" 이라는 새로운 방법을 개발하였다. 이 방법은 별의 공간 좌표와 색-등급도 상에서 위치를 동시에 고려하여 구성원 확률을 구하는 독창적인 방법이다. 본 발표에서는 이 방법을 적용한 결과를 고유운동으로 얻은 구성원확률과 비교하고, 몬테칼로 시뮬레이션으로 검증한 결과를 소개하고자 한다. 우리의 방법을 통하여, 은하면에 있는 다양하고 많은 산개성단에 대하여 관측연구를 수행한다면, 다양한 조석꼬리의 가능성 검증을 할 수 있고, 은하와 성단의 상호 작용과 역학적 진화에 대한 이해의 폭을 넓힐 수 있을 것으로 기대한다.We present the interim results of simultaneous time monitoring observations of$^{28}SiO$ v = 1, 2, J = 1-0,$^{29}SiO$ v = 0, J = 1-0 and$H_2O$ $6_{16}-5_{23}$ maser lines toward 10 known water fountain sources at a post-AGB stage. The observations have been carried out from 2009 June to 2013 September using the 21m single dish radio telescopes of the Korean VLBI Network. From six sources, we detected well separated red- and blue-shifted$H_2O$ maser features with large velocity ranges more than 100 km$s^{-1}$ . From four sources, we detected red- and/or blue-shifted$H_2O$ maser features depended on observational epochs. However, we could not detected SiO maser emission from any sources and any epochs. For a representative water fountain source W43A, we obtained$H_2O$ maser spectra at 17 epochs which show a clear bipolar and discontinuous mass ejections. They also showed a periodic change between red-shifted and blue-shifted peaks. However, we need a more regular and short-time interval monitoring observations in order to fix the period and peak intensity variation interval.The hierarchical model of galaxy formation predicts that galaxy halos contain merger relics in the form of long stellar stream. Thus, tidal substructure of stars around globular clusters, such as tidal tails, could be an essential evidence of the merging scenario in the formation of the Galaxy. From April 2010 to December 2012, we obtained$45^{\prime}{\times}45^{\prime}$ wide-field JHKs near-infrared photometric imaging data for about 20 globular clusters in the Milky Way, and examined the stellar density distribution around globular clusters. Here, we introduce the preliminary results of stellar spatial distributions and radial surface density profiles of four globular clusters. In order to minimize the field star contamination and identify the cluster's member candidates stars, we used a statistical filtering algorithm and gave weights on the CMDs of globular clusters. In two-dimensional stellar density maps, we could found tidal stripping structures for some globular clusters. The orientation of tidal substructure seems to associate with the effects of dynamical interactions with the Galaxy and cluster's orbit. Indeed, the radial surface density profile accurately describes this stripping structures as a break in the slope of profile. The observational results could give us further observational evidence of merging scenario of the formation of the Galaxy.외계행성 연구는 외계생명체 발견과 밀접한 관계가 있으므로 선진국에서는 국가중점연구로 지정하여 연구에 집중하고 있는 기초학문 연구분야다. 기초학문 연구분야이다. 외계행성 연구는 현재까지 발견을 위주로 행해져 왔고, 그 결과 수백 개의 외계행성이 발견되는 성과를 얻을 수 있었다. 최근에는 지구의 크기와 온도에 근접하는 외계행성이 발견이 언론에 소개 되기도 하였다. 외계행성의 분광 연구는 지금까지 그 밝기가 아주 어두운 관계로 Broad band 관측이 주로 행해졌다 (e.g., Swain et al. 2010). 그러나 최근 3-m급 망원경과 중분산 분광기를 사용한 연구에서 구체적인 적외선 분광구조가 드러나게 되었다 (e.g., Waldmann et al. 2012). 따라서 앞으로 GMT의 분광기를 사용하여 상당히 구체적인 분광구조 관측이 가능하리라고 예측 할 수 있게되었다. 이번 발표에서는 GMT분광기들을 사용한 외계행성 적외선 분광 연구를 원활히 수행하기 위한 준비 단계로 태양계 행성에 대한 국내외 적외선 분광 연구 현황을 논의 하고자 한다.We present new integrated spectroscopy of 24 Galactic globular clusters, observed with the Isaac Newton Telescope in La Palma. Spectra have been extracted from one core radius for each cluster, achieving high wavelength resolution of FWHM${\sim}2.0^{\circ}A$ . In combination with two previous data sets from Puzia et al. 2002 and Schiavon et al. 2005, we construct the largest database of the Lick indices for total 53 Galactic globular clusters. The empirical metallicity.index relations are given for the 20 Lick indices for the use of deriving metallicities of remote, unresolved stellar systems.The distributions of Horizontal Branch (HB) star color, temperature, and mass encode a great deal of information on the stellar evolutionary and (possibly) dynamical processes taking place in Globular Clusters (GCs). An accurate physical modeling of the Red Giant Branch (RGB) mass-loss process is key to solving the so-called second parameter problem. In my poster I will present the most recent advancements of an analytical model for mass-loss along the RGB. The model predicts the HB mass distribution with remarkable accuracy over a sample of 4 GCs. These results were submitted as a paper to ApJ (Pasquato et al. 2013, ApJ submitted), but here I expand on them presenting refinements to the model and a comparison with HB masses obtained from Galex ultraviolet observations.The GMT project is moving ahead smoothly and is approaching the construction phase expected to begin around mid 2014. In this contribution, we will introduce the status of activities being made for the preparation of construction phase, including the Preliminary Design Review of sub-systems, the casting of primary mirror segments, and the GMT retreat.K-GMT Science Group (KGSG) is in charge of overall science operations with an aim to promote scientific activities of Korean Astronomical Community for the GMT era in 2020. KGSG is currently running and/or promoting K-GMT Science Program, K-GMT Science White Paper Initiative, and K-GMT Summer School for Young Researchers. KGSG is also planning to join several international survey projects such as SDSS IV and LSST. We will introduce the current status on various operations and the future plan for KGSG to the community members.Pyo, Jeonghyun;Jeong, Woong-Seob;Lee, Dae-Hee;Matsumoto, Toshio;Moon, Bongkon;Tsumura, Kohji;Park, Kwijong;Park, Sung-Joon;Park, Youngsik;Kim, Il-Jung;Park, Won-Kee;Han, Wonyong;Im, Myungshin;Lee, Hyung Mok;Lee, Jeong-Eun 82.1
The SPICA (SPace Infrared Telescope for Cosmology & Astrophysics) project is a next-generation infrared space telescope optimized for mid- and far-infrared observation with a cryogenically cooled 3m-class telescope. Owing to unprecedented sensitivity and high spatial resolution, the focal plane instruments are expected to perform the confusion-limited observation. The SPICA will challenge to reveal many astronomical key issues from the star-formation history of the universe to the planetary formation. The Korean 5contribution to SPICA as an international collaboration is the development of the near-infrared instrument, FPC (Focal Plane Camera). The Korean consortium for FPC proposed a key system instrument for the purpose of a fine guiding (FPC-G) complementing the AOCS (Attitude and Orbit Control System). The back-up instrument of FPC-G, FPC-S will be responsible for the scientific observations as well. Through the international review process, we have revised the scientific programs and made the feasibility study for the fine guiding system. Here, we report the current status of SPICA/FPC project.Jeong, Woong-Seob;Park, Sung-Joon;Park, Kwijong;Lee, Dae-Hee;Moon, Bongkon;Pyo, Jeonghyun;Park, Youngsik;Kim, Il-Joong;Park, Won-Kee;Lee, Duk-Hang;Park, Chan;Ko, Kyeongyeon;Nam, Ukwon;Han, Wonyong;Im, Myungshin;Lee, Hyung Mok;Lee, Jeong-Eun;Shin, Goo-Hwan;Chae, Jangsoo 82.2
The NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1 is being developed by KASI. The NISS will perform the imaging low-resolution spectroscopic observation in the near-infrared range for nearby galaxies, low background regions, starforming regions and so on. The off-axis reflecting telescope with a wide field of view (2 deg.${\times}$ 2 deg.) will be operated in the wavelength range from 0.95 to$3.8{\mu}m$ . In order to reduce thermal noise, a telescope and a HgCdTe infrared sensor will be cooled down to 200K and 80K, respectively. To evade a stray light outside a field of view and use limited space efficiently, the NISS adopted the off-axis reflective optical system. The primary and secondary mirrors, optomechanical part and mechanical structure were designed to use the same material. It will lessen the degradation of optical performance due to a thermal variation. The purpose of NISS is the observation of cosmic near-infrared background in the wide wavelength range as well as the detection of near-infrared spectral lines in nearby galaxies, cluster of galaxies and star forming regions. It will give us less biased information on the star formation history. In addition, we will demonstrate the space technologies related to the development of the Korea's leading near-infrared instrument for the future large infrared telescope, SPICA.Kim, Sanghyuk;Pak, Soojong;Kim, Geon Hee;Lee, Gil Jae;Lee, Jong-Ho;Lee, Su-Min;Chang, Seunghyuk;Im, Myungshin;Lee, Hyuckee 83.1
선형비점수차를 완벽하게 제거한 비축반사경 이론을 천체 관측용 분광기의 전단 광학계 등에 응용하면 색수차가 없는 기기 제작이 가능하다. 이러한 비축 반사경은 DTM(Diamond Turning Machine)을 이용하여 알루미늄으로 만들면 제작 시간이 단축된다. 그러나 DTM을 이용해 알루미늄과 같이 무른 금속을 가공할 경우 툴마크가 발생하게 된다. 툴마크는 회절현상을 발생시키며 이러한 회절현상은 알루미늄 반사경을 이용한 광학계 개발에 제약이 된다. 툴마크는 DTM 가공 이후 연마를 통해 제거할 수 있지만 알루미늄의 무른 특성으로 인해 연마 과정에서 반사경의 형상이 변할 가능성이 크다. 이러한 알루미늄 반사경의 형상 변화를 최소화하기 위한 방법으로는 알루미늄 반사경 표면에 무전해니켈도금을 하는 것이다. 하지만 도금 과정에서 반사경의 형상이 변할 가능성이 있기 때문에 두가지 방법을 사용하여 툴마크를 제거할 계획이다. 첫 번째 방법은 DTM 가공된 알루미늄 반사경을 5 um의 무전해니켈도금 이후 연마하여 툴마크를 제거하고 반사율 증가를 위해 그 위에 다시 알루미늄 코팅을 하는 방법니다. 두 번째 방법은 100 um의 무전해니켈도금 이후 DTM 가공을 하고 다시 연마를 통해 툴마크를 제거하는 방법이다. 이번 발표에서는 툴마크를 제거하기 위한 2가지 방법의 장단점을 확인하고 툴마크를 제거한 알루미늄 반사경을 제작하기 위한 과정을 설명하였다. 본 연구에서 개발한 비축 반사경은 서울대학교 창의연구단의 광학/적외선 카메라 CQUEAN의 차세대 모델에 적용할 계획이다.Choi, Nahyun;Lee, Hye-In;Pak, Soojong;Ji, Tae-Geun;Jeong, Byeongjoon;Bae, Min K.;Im, Myungshin 83.2
Camera for QUasars in EArly uNiverse (CQUEAN) is an optical CCD camera developed by the Center for the Exploration of the Origin of the Universe (CEOU). In 2010 August, CQUEAN was attached on the 2.1m Otto Struve Telescope at the McDonald Observatory in Texas, USA. As the main purpose of CQUEAN is detecting the Lyman breaks of redshift ~5 quasars, it is sensitive to near-infrared wavelengths (0.7-1.0${\mu}m$ ). For the auto-guiding system, it is using a rotating guide arm to find guide stars on the Cassegrain off-axis focus of the telescope. We plan to upgrade a new filter wheel system consists of a series of narrow band filters. We will install this independent auto-guiding units on the finder scope, which makes rooms on the Cassegrain focal plane of the main telescope. In this presentation we present the system architecture of the CQUEAN Auto-guiding Package (CAP).Sim, Chae Kyung;Le, Huynh Anh Nguyen;Pak, Soojong;Lee, Hye-In;Kang, Wonseok;Chun, Moo-Young;Jeong, Ueejeong;Yuk, In-Soo;Kim, Kang-Min;Park, Chan;Jaffe, Daniel T.;Pavel, Michael 84.1
We present a python-based data reduction pipeline for the Immersion GRating INfrared Spectrograph (IGRINS). IGRINS covers the complete H- and K-bands in a single exposure with a spectral resolving power of greater than 40,000. IGRINS is designed to be compatible with telescopes of diameters ranging from 2.7-m (the Harlan J. Smith telescope at McDonald Observatory) to 8-10m. Commissioning and initial operation will be on the 2.7-m telescope from late 2013. The pipeline package is a part of the IGRINS software and designed to be compatible with other package that maneuvers the spectrograph during the observation. This package provides high-quality spectra with minimal human intervention and the processes of order extraction, distortion correction, and wavelength calibration can be automatically carried out using the predefined functions (e.g. echellogram mapping and 2D transform). Since the IGRINS is a prototype of the Giant Magellan Telescope Near-Infrared Spectrometer (GMTNIRS), this pipeline will be extended to the GMTNIRS software.KVN 샘플러의 국산화를 위하여, 우리는 지난 3년간의 연구로 1GHz 샘플러 Proto-Type을 설계하고 제작하였다. 첨단망인 KREONET을 이용하여 각 전파천문대를 연결하고, 바로 대전 센터로 관측 데이터를 전송하는 e-VLBI를 구현할 수 있다면, 연구의 가치와 효율을 극대화 할 수 있다. 이를 위하여 샘플러에서 직접 첨단망으로 VDIF(VLBI Data Interchange Format, VLBI 자료전송 규격)의 자료를 보낼 수 있게 새로운 샘플러를 설계하고 제작하고자 한다.Koh, Ju Heon;Kim, Young-Soo;Jung, Ho June;Jung, Hwa Kyoung;Yang, Ho-Soon;Kim, Ho-Sang;Lee, Kyoung-Don;Cho, Myung;Park, Won Hyun;Ahn, Hyo-Sung;Hwang, Narae;Yuk, In-Soo;Park, Byeong-Gon 85.1
GMT(Giant Magellan Telescope)는 25.4m의 주경과 3.2m의 부경으로 이루어진 거대망원경이다. 3.2m의 부경은 빠른 tip-tilt로 망원경을 제어하는 Fast Steering Mirror(FSM)와 적응광학계로 이루어진 Adaptive Secondary Mirror (ASM)로 구분된다. 한국천문연구원은 국내외 협력기관들과 함께 부경 FSM의 시험모델개발을 수행하고 있다. 부경은 1.06m의 반사경 일곱 개로 이루어져 있는데, 한 개의 광축 반사경 주위로 여섯개의 비축 반사경이 둘러싸여서 하나의 3.2m 반사경과 같은 기능을 하고 있다. 비축 비구면 반사경에 대한 시험모델의 반사면을 가공한 결과 표면가공 정밀도가 11.7nm rms의 정밀도를 갖는 반사경을 가공하였다(target : <20nm rms). 또한 test-bed를 제작하여 tip-tilt 정밀도를 제어한 결과 성능요구 조건 값인 0.03arcsec 제어에 성공하였고, 더 나아가 0.01arcsec의 tip-tilt 제어도 가능한 것으로 판단된다.Lee, Hye-In;Pak, Soojong;Sim, Chae Kyung;Kang, Wonseok;Chun, Moo-Young;Jeong, Ueejeong;Yuk, In-Soo;Kim, Kangmin;Park, Chan 85.2
We developed autoguiding system for IGRINS (Immersion Grating Infrared Spectrograph) which is a high resolution near-IR spectrograph. This instrument will be attached on the 2.7m telescope at the McDonald observatory in 2013 November. IGRINS consists of three near-Infrared detector modules, i. e., H and K band spectrograph modules and a K band slit camera module, within which we are using the slit camera for autoguiding of the telescope. Comparing to typical optical CCDs, however, the infrared array shows non-uniform responses, higher noises, and many bad pixels. In this poster, we present methods to improve center finding functions and algorithms for the infrared array and the simulator test results of the IGRINS Slit-Camera Package.Observations of a filament showing an activated barb recorded from the at the Dutch Open Telescope (DOT) on 2010 August 20 are presented. The filament developed a barb in 10 minutes, which disappeared within the next 35 minutes. Such a rapid formation and disappearance of a filament barb is unusual, and has been seldom reported. Line-of-sight velocity maps were constructed from images in seven line positions along the H-alpha line. We observe flows in the filament spine towards the barb location prior to its formation, and flows in the barb towards the spine during its disappearance. Photospheric magnetograms from Helioseismic Magnetic Imager on board the Solar Dynamics Observatory were used to determine the changes in magnetic flux in the region surrounding the barb location. The variation of magnetic flux in this duration support the view that barbs are rooted in minor magnetic polarity.Ellerman bombs(EBs) are emission features at the wings of the H alpha spectral line. They are believed to be a kind of a magnetic reconnection feature in the low chromosphere or near photosphere. It was previously reported that surges often occur in association with EBs. However, previous observations were restricted to imaging observation. Using Fast Imaging Solar Spectrograph installed in New Solar Telescope at Big Bear Solar Observatory, California, we observed 5 EBs and associated surges with high-spatial and high-spectral resolutions. In this presentation, we will show the results and discuss the physical properties.Ellerman bombs(EB) are small-scale bright features observed best in the wings of H alpha line. We used the Fast Imaging Solar Spectrograph(FISS) with the 1.6m New Solar Telescope at Big Bear Solar Observatory, in order to investigate characteristics of each EB. We analyzed H alpha line profiles of EBs, and classified EBs by their contrast profiles. To analyse characteristics of EBs, we applied power-law fitting ($C={\alpha}{\Delta}{\lambda}^{-n}$ ) to the EB contrast profiles. The amplitude${\alpha}$ is a measure of the strength of an EB event (or the amount of released energy), and the power-law index n is a measure of spatial concentration of energy in the higher layers of the solar atmosphere. With the two parameters, we classified EBs into a few groups. We try to understand the physical properties of each group.We studied a fine-scale half ring-like structure around a pore seen from the high spectral and the high spatial resolution data. Our observations were carried out using the Fast Imaging Solar Spectrograph (FISS) and the InfraRed Imaging Magnetograph (IRIM) installed at the 1.6 meter New Solar Telescope of Big Bear Solar Observatory (BBSO) on 2012 July 19. During the observations, we found a fine-scale half ring-like structure located very close to a pore (~0.4 arcsec apart from the pore). It was seen in the far wing images of the$H{\alpha}$ and Ca II$8542{\AA}$ lines, but it was not seen in the line center images of two lines. The length of the structure is about 4200 km and the width is about 350 km. We determined its line-of-sight velocity using the Doppler shift of the centroid of the Ti II line ($6559.6{\AA}$ , close to the$H{\alpha}$ line) and determined horizontal velocity using the NAVE method. we also investigated the magnetic configurations using the Stokes I, Q, U, and V maps of the IRIM. As a results, we found that it has a high blue-shift velocity (~2km) faster than the photospheric features and has a strong horizontal component of the magnetic field. Based on our findings, we suggest that it is associated with small flux emergence, which occurs very close to the pore. Even though it is very small structure, this kind of magnetic configuration can be in chare of the upper chromosphere heating, especially above the pore.Cho, Kyung-Suk;Bong, Su-Chan;Lim, Eun-Kyung;Cho, Il-Hyun;Kim, Yeon-Han;Park, Young-Deuk;Yang, Heesu;Park, Hyung-Min;Chae, Jongchul 88.1
We have investigated vertical motions of plasma in the pores and changes of the motions with height by using high time and spatial resolutions data obtained by the Fast Imaging Solar Spectrograph (FISS) of the 1.6 meter New Solar Telescope (NST). We infer the LOS velocity by applying the bisector method to the wings of CaII 854.2 nm line profile. We find that (1) upflow velocity in the pores decreases with height and turns into downward in the upper chromosphere; (2) 3 min and 5 min oscillations are found from the Doppler velocity in the pore at various wavelengths from the wing (${\pm}2.35{\AA}$ ) to the core (${\pm}1.25{\AA}$ ) of the CaII line; and (3) power of high (low) frequency oscillation obtained from the CaII intensity increases (decreases) with height. We discuss the physical implications of our results in view of the connection of LOS plasma flows in a concentrated magnetic flux (pore) between the photosphere and the low chromosphere.Exploration of the wave-mode identification and its propagating property in the solar pore is desirable to study the energy transfer in the solar atmosphere. The Fast Imaging Solar Spectrograph (FISS) installed at the New Solar Telescope (NST) is a unique system that can do imaging of H-alpha and Ca II 8542 band simultaneously, which is quite suitable for studying of dynamics of chromosphere. In this study, we inspect a relationship between the cross-sectional area and intensity of the pore at continuum (-0.4 nm) near the Ca II line. We find coherent oscillations of the area and intensity. They shows out-of-phase (~ 180 degree difference) in photosphere, which implies that the oscillation is fast sausage mode. We also investigate a relationship between LOS velocities above the pore obtained from the Ca II and the Ha line cores, and find no significant difference of the phase (~10 degree) between the formation heights of the lines in chromosphere.We present a multiwavelength study of the X-class flare, which occurred in active region (AR) NOAA 11339 on 3 November 2011. The EUV images recorded by SDO/AIA show the activation of a remote filament (located north of the AR) with footpoint brightenings about 50 min prior to the flare occurrence. The kinked filament rises-up slowly and after reaching a projected height of ~49 Mm, it bends and falls freely near the AR, where the X-class flare was triggered. Dynamic radio spectrum from the Green Bank Solar Radio Burst Spectrometer (GBSRBS) shows simultaneous detection of both positive and negative drifting pulsating structures (DPSs) in the decimetric radio frequencies (500-1200 MHz) during the impulsive phase of the flare. The global negative DPSs in solar flares are generally interpreted as a signature of electron acceleration related to the upward moving plasmoids in the solar corona. The EUV images from AIA$94{\AA}$ reveal the ejection of multiple plasmoids, which move simultaneously upward and downward in the corona during the magnetic reconnection. The estimated speeds of the upward and downward moving plasmoids are ~152-362 and ~83-254 km/s, respectively. These observations strongly support the recent numerical simulations of the formation and interaction of multiple plasmoids due to tearing of the current-sheet structure. On the basis of our analysis, we suggest that the simultaneous detection of both the negative and positive DPSs is most likely generated by the interaction/coalescence of the multiple plasmoids moving upward and downward along the current-sheet structure during the magnetic reconnection process. Moreover, the differential emission measure (DEM) analysis of the active region reveals presence of a hot flux-rope structure (visible in AIA 131 and$94{\AA}$ ) prior to the flare initiation and ejection of the multi-temperature plasmoids during the flare impulsive phase.Solar energetic transients, e.g., flares, CMEs, etc., release large amount of energy which is expected to excite acoustic waves (p-modes) by exerting mechanical impulse of the thermal expansion of the flare on the photosphere. We study the p-mode properties of flaring and dormant active regions (ARs) to find association between flare and p-mode parameters. We compute the magnetic and flare activity indices of ARs using the line-of-sight magnetograms and GOES X-ray fluxes, respectively. The p-mode parameters are computed from the ring-diagram analysis. We correct p-mode parameters for magnetic field, filling factors and foreshortening by multiple linear-regression analysis. Our analysis of several flaring and dormant ARs observed during the Carrington rotations 1980-2109, showed strong association of mode parameters with magnetic and flare activities. We find that the mode parameters are contaminated by the geometrical effect. Mode amplitude decreases with angular distance from the solar disc centre. The mode width increases with magnetic activity while amplitude showed opposite relation due to mode absorption by the sunspot. After correcting modes due to all geometrical effects, magnetic activity and filling factor, we find that the modes amplitude, and mode energy increases with flare energy while width shows opposite relation.To better understand the physics underlying the eruption of prominences in solar active regions, we studied eruption processes of two active prominences located in the active region NOAA 11261 using multi-wavelength observational data with high temporal and spatial resolution. Specifically, we examined (1) the temporal variation of morphology and plasma properties of the two active prominences, (2) magnetic fields and their evolution on the photospheric surface underneath the prominences, and (3) the time profiles and locations of radio, EUV, and soft/hard X-ray emissions produced by the M9.3 flare related to the prominence eruption. As a result, we found that: (1) a prominence F1 began to erupt and expand as the abrupt and intense EUV brightening occurred in the localized region underneath the western part of F1 at 03:45 UT prior to the peak time of the M9.3 flare, (2) F1 split into two parts: i.e., the western part asymmetrically erupted by producing the M9.3 flare with microwave source motions along the magnetic polarity inversion line between the two flare ribbons, while the eastern part coalesced into a pre-existing prominence F2, (3) F2 became unstable due to the coalescence with the eastern part of F1, and then it partially erupted with clockwise untwisting motions.Filament eruptions are one of the energetic phenomena on the solar surface with flares and coronal mass ejections (CMEs). We observed the whole process of filament eruption that occurred in AR 11305 in association with a C5.6 flare on 2011 September 29th using the Fast Imaging Solar Spectrograph (FISS) and the Solar Dynamics Observatory (SDO). The eruption consists of a slow phase with a transverse speed of ~10 km$s^{-1}$ in 16 minutes and a fast phase with a transverse speed of ~200 km$s^{-1}$ in 3 minutes. Near the beginning of slow phase eruption, preflare brightening occurred beneath the filament in$H{\alpha}$ and some EUV images. The preflare brightening region is associated with a blue-shifted$H{\alpha}$ feature with a speed of ~60 km$s^{-1}$ . It appears that this is the outflow from magnetic reconnection which may have occurred at relatively low atmosphere. Our result support the notion that the preflare brightening is a process of magnetic reconnection playing an important role in triggering the filament eruption by deformative the magnetic field lines under the eruptive filament.Since 2010, we have improved the Fast Imaging Solar Spectrograph (FISS) and observed the Sun. From the early observations we noticed two instrumental problems: poorer spatial resolution due to chromatic aberration and lower light level in the Ca II band. We tried to overcome these problems in two ways. First, we updated the relay optics. With the new one, we don't find any noticeable chromatic aberration between Ha and CaII and as a result can obtain the high resolution data in Ca II as well. Second, we replaced mirrors and the grating. This resulted in the increase of light level by a factor of up to 2.5, and hence in the high S/N ratio. The images constructed from the recentest observations indicate that the performance of the FISS is now much closer to our original intention than at the beginning.The Korean Solar Radio Burst Locator (KSRBL) is a solar radio spectrograph observing the frequency range between 0.245-18 GHz with the capability of locating the wideband gyrosynchrotron bursts. Its calibration process consists of antenna calibration, flux calibration, and demodulation. Antenna calibration is to determine the position, the width, and the peak value of the beam, flux calibration is to determine the conversion factor between the measured unit to the Solar Flux Unit (SFU), and demodulation is to determine the burst position and remove the modulation pattern. We introduce the current calibration software and some information that potential users may concern.In this study, we examined chromospheric oscillation signatures in two solar active regions, a limb active region and a sunspot with a light bridge, observed by the Fast Imaging Solar Spectrograph (FISS) of the 1.6m New Solar Telescope (NST) at Big Bear Solar Observatory. The FISS is a slit spectrograph with a fast imaging capability and can observe the solar chromosphere in$H{\alpha}$ and Ca II$8542{\AA}$ bands simultaneously with high spectral resolutions. After dark and flat correction, we compensated for image rotation at the Coude focus and made image alignment. We estimated Doppler shifts over active regions using the bisector method and investigated the temporal and spatial fluctuations of Doppler shifts for some selected cases. And we obtain the power map by using the Lomb-Scargle periodogram technique to examine the oscillation power at different features. Finally, we will discuss our results and implications.We revisit the 1.3-year (yr) signals observed on the Sun, in the interplanetary space, and in the Earth's magnetosphere to study the coupling among signals from the three regions for about forty years (1970--2007) covering three solar cycles 21, 22, and 23. For this, we make dynamic spectra of datasets including three different regions. From this, we estimate the peak frequency around 1.3 yr for each region and the corresponding band power. We found that coherent power only appears during 1987-1995 and the coherent behavior is found only in the interplanetary space and Earth, not in the Sun. Although the solar surface magnetic field shows significant power around 1.3 yr, their peak frequencies are statistically different from those of the outer regions, which make us to dismiss the existence of coherence among the three regions. But it is notable that the peaks in band power corresponding to the 1.3-yr period are clearly simultaneous in the interplanetary space and Earth.Cho, Junghee;Lee, Dae-Young;Shin, Dae-Kyu;Kim, Jin-Hee;Park, Mi-Young;Kim, Thomas Kyoung-Ho 93.1
The Earth's radiation belts consist of an inner belt and an outer belt, being separated by the slot region. It is well known that the variations of the inner edge of the outer belt and the location of the plasmapause (Lpp) are closely related to each other. Different waves exist inside and outside the plasmasphere, playing different roles in the particle dynamics. The plasmapause is well known to be influenced by solar wind conditions and geomagnetic disturbances. Therefore, it is important to precisely determine the location of the plasmapause and develop a prediction scheme. In this study, we identified the location of the plasmapause using the plasma density data from the Time History of Events and Macroscale Interactions During Substorms (THEMIS). The plasmapause is determined by requiring density gradient of a factor of 15 within L-change = 0.5. We statistically determined Lpp as a function of preceding geomagnetic indices. Also, we determined the relations between Lpp and preceding solar wind conditions by estimating correlation coefficients. These relations give us predicting models of Lpp as a function of preceding solar wind parameters and geomagnetic indices. As our database covers a period over the ascending phase from near-sunspot minimum, our statistical results differ somewhat from previous works that cover near-sunspot maximum. Finally, we give some comparative examples obtained from the Van Allen Probes data.Polarization of the light scattered by the lunar surface contains information on the mean particle size of the lunar regolith, which gradually decreases by continued micro-meteoroid impact over a long period and thus is an age indicator of the surface. We performed multi-band (U, B, V, R and I) polarimetric observations toward the whole near side of the Moon at the Lick observatory using a 15-cm reflecting telescope with 1.1km/pixel spatial resolution at the center of the lunar disk. We analyze the color dependence of the polarization properties of the lunar regolith and discuss its implication for the study of lunar swirls.Whistler mode chorus waves, which are observed outside the plasmasphere of the Earth's magnetosphere, play a major role in accelerating and scattering energetic electrons in the radiation belts. In this study we developed a predicting scheme of the global distribution of chorus by using the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite data. First, we determined global spatial distributions of chorus activity, and identified fit functions that best represent chorus intensities in specific L-MLT zones. Second, we determined the specific dependence of average chorus intensity on preceding solar wind conditions (e.g., solar wind speed, IMF Bz, energy coupling degree) as well as preceding geomagnetic states (as represented by AE, for example). Finally, we combined these two results to develop the predicting functions for the global distribution and intensity of chorus. Implementing these results in the radiation belt models should improve the local acceleration effect by chorus waves.We studied the precipitation of magnetospheric energetic electrons into the Earth's atmosphere during magnetic storm times using precipitating electron flux data from the MEPED on board the NOAA Polar Orbiting Environmental Satellites (POES) low.altitude satellite, NOAA-16. We identified a total of 84 storm events between 2001 and 2012 using SYM-H index. We have done a superposition of precipitating electron fluxes for each of three energy ranges (i.e., e1: > 30 keV, e2: > 100 keV, e3: > 300 keV) for the identified storm times. The results show that the fluxes start to increase before the main phase of storm for all energy ranges and reach a maximum level just before the time of SYM-H minimum value. The precipitation timescales are energy-dependent, being shorter for lower energy, ~4.67 hours for e1, ~7.93 hours for e2 and ~26.5 hours for e3. The precipitating fluxes decline during the recovery phase of the storms. We examined the L shell dependence of the precipitating electron flux during the main phase. We found that statistically the precipitation fluxes are dominantly seen at L of ~ 3-4 or higher. This L value roughly corresponds to the plasmapause location during the main phase. Thus the results imply that the electron precipitation mainly occurs outside of the plasmapause. In addition, we classified the storm events by their strength and examined the dependence of precipitation on storm intensity. We found that the electron precipitation occurs on a faster time scale and penetrate into inner L shell region for a stronger storm.The RBSPICE (Radiation Belt Storm Probes Ion Composition Experiment) is one of five instrument suites onboard the twin Van Allan Probes (or Radiation Belt Storm Probes; RBSP), launched August 30, 2012 by NASA. One of science targets of RBSPICE instrument is to determine "how changes in that ring current affect the creation, acceleration, and loss of radiation belt particles?". For that purpose, it measures ions and electrons simultaneously. Ion's energy range is from ~20 keV to ~1 MeV and electron's energy channel is from ~35 keV to 1 MeV in order to provide supplementary information about the radiation belts. In this paper, we investigate a reliability of the electron flux measured from the RBSPICE by comparing with ECT (The Energetic Particle, Composition and Thermal Plasma Suite) data. We found there is a critical proton contamination problem in the electron channels of ~ 1MeV of RBSPICE observations during one moderate storm event of Sym H ~ -76 nT on March 1, 2013.The Van Allen Probes were designed to study the Earth's radiation belts on various scales of space and time. The identical two spacecrafts going nearly eccentric orbits lap each other several times over the course of the mission and each probe carries five instrument suites to address the science objectives on the radiation belt. Since Van Allen Probes launched on August 30, 2012, the probes detecte several storm events up to now. To understand the particle acceleration and loss mechanism in the radiation belt, we first focus on the energetic electrons' dynamics detected by ECT (Energetic Particle, Composition, and Thermal Plasma Suite). ECT measures near-Earth space's radiation particles covering the full electron and ion spectra from ~ eV to 10's of MeV with sufficient energy resolution. In this paper, we present the preliminary results of the recent several storm events using electron data from ECT(MagEIS and REPT).A Forbush decrease(FD) is a depression of cosmic ray intensity observed by ground-based neutron monitors(NMs). The cosmic ray intensity is thought to be modulated by the heliospheric magnetic structures including the interplanetary coronal mass ejection(ICME) surrounding the Earth. The different magnitude of the decreasing in intensity at each NM was explained only by the geomagnetic cutoff rigidity of NM station. However, sometimes NMs of the almost same rigidity in northern and southern hemispheres observe the asymmetric intensity depression magnitudes of FD events. Thus, in this study we intend to see the effects on cosmic ray intensity depression rate of FD event recorded at different NMs due to different ICME propagation direction as an additional parameter in the model explaining the cosmic ray modulation. Fortunately, since 2006 the coronagraphs of twin spacecraft of the STEREO mission allow us to infer the propagation direction of ICME associated with the FD event in 3-dimension with respect to the Earth. We confirm that the asymmetric cosmic ray decreasing modulations of FD events are determined by the propagation directions of the associated ICMEs.The solar images are taken by the CCD detectors of the Sun monitoring satellites. The solar images are constructed after removing the traces of cosmic rays on the raw CCD data files. Thus, while applying the method of removing the cosmic rays traces, we can estimate the cosmic rays flux by counting the number of traces. The cosmic ray flux in the steady state might be the sum of the solar and galactic cosmic rays. However, the abrupt change in the flux could be assumed to be originated from the Sun. Therefore, we can identify the solar origins of the sudden solar cosmic ray flux changes from the phenomena shown in the processed solar images taken by SOHO/EIT. As the results, the estimated cosmic ray flux in the steady state is the anti-correlated with sunspot numbers, which shows the minima in cosmic ray flux at the solar cycle maxima defined by the sunspot numbers. The profiles of estimated solar cosmic ray associated with the ground level enhancements have the significant increase in the cosmic ray flux with good correlation. Thus, the solar images are valuable data useful in estimating the solar cosmic ray long term and transient flux variations.적외선 분광 관측은 상대적으로 온도가 낮은 태양계 천체를 연구하는데 있어서 매우 강력한 관측 기술이다. 특히 근적외선 및 중적외선 분광선은 태양계 천체의 지표 및 대기의 성질에 대해서 많은 정보를 주는 파장대이다. 따라서 우주탐사선 뿐만 아니라 지상 망원경으로도 근적외선 및 중적외선 영역의 분광관측은 지속적으로 관측이 수행되고 있는 영역이다. 이렇게 획득된 분광선은 모델링의 과정을 통하여 천체의 구성성분, 생성 과정 및 생성 시기, 물리, 화학적 진화 등을 연구할 수 있다. 본 연구에서 개발 중인 3~5 micron 중적외선 분광기 지상모델은 향후 태양계 천체들에서 물 또는 얼음을 찾을 수 있는 가능성이 있는 파장대이며, 또한 국내에서 개발된 적이 없는 파장대이다. 본 연구에서는 우주탐사선에 탑재된 중적외선 분광기에 의해 관측된 지표를 가진 태양계 천체 (수성, 금성, 화성, 타이탄, 혜성, 소행성)들의 연구 사례를 조사하였다. 이 자료는 본 연구에서 개발하고자 하는 중적외선 분광기 지상모델의 완성 단계에서 지표를 가진 태양계 천체, 특히 달에 대한 과학적 임무를 결정하는데 중요한 역할을 할 것으로 기대하고 있다.달 및 행성탐사선에 탑재된 적외선 분광기는 태양계 행성들의 지표 및 대기 성분 관측을 위해 널리 활용되고 있다. 적외선 분광기 관측 영역 중$3-5{\mu}m$ 파장 대에서는 행성의 지표 및 대기에 존재하는 물(얼음), 이산화탄소, 일산화탄소, 메탄, 중수와 같은 여러 성분의 분광선 관측이 가능하다. 이 파장대를 관측한 해외 탐사선 탑재체 사례로는 화성의 경우 Mars Express에 탑재된 OMEGA와 PFS, 소행성의 경우 ROSETTA에 탑재된 VIRTIS 등이 해당된다.$3-5{\mu}m$ 파장대의 분광기는 국내에서 개발 사례가 없으며 해외에서도 달 탐사선에 탑재된 바가 없어 달 얼음과 관련된 다른 파장대의 자료와 상호보완이 가능한 자료를 제공할 것으로 기대된다. 본 연구에서는 달 및 행성탐사를 위한$3-5{\mu}m$ 파장 영역을 탐사하는 적외선 분광기의 요구사양을 그 과학임무에 비추어 제안하고자 한다.Lee, Joon Hyeop;Hwang, Narae;Lim, Youn Ju;Park, Byeong-Gon;Lee, Jae-Joon;Jung, Hwa Kyoung;Kim, Yee Jin 100.1
다가오는 거대마젤란망원경 (GMT) 시대를 이끌어갈 신진 연구자들의 연구역량 증진을 위해, 2013년 8월 27일부터 30일까지 3박4일에 걸쳐 강원도 홍천 가람밸리 리조트에서 제3회 거대마젤란망원경 여름학교를 개최한다. 총 47명의 대학원생과 박사후연구원들이 참여하는 이번 여름학교에서는, GMT 개관, 1세대 관측기기 가운데 최초로 활용될 계획인 GMACS와 G-CLEF의 소개 및 그것들을 활용한 대표적인 과학연구 분야에 대한 강의가 이루어진다. 또한 계절학교 참가자들이 'GMACS 또는 G-CLEF를 활용한 관측연구 제안'이라는 주제로 직접 토론과 발표에 참가하는 조별 활동이 주된 프로그램으로 추가된다. 이러한 여름학교 프로그램은 신진 연구자들이 GMT를 활용한 다양한 연구 가능성을 경험하고 서로 능동적으로 교류할 수 있는 계기가 될 것으로 기대된다. 2013년도부터 새로운 방식으로 시도되는 제3회 거대마젤란망원경 계절학교 결과를 정리함으로써 앞으로 나아갈 계절학교의 방향을 점검해본다.외계행성 탐색은 현재 천문학계에서 가장 활발하게 진행되고 있는 연구 분야들 중 하나이며 우리나라에서도 외계행성 탐색을 위한 KMTNet 프로젝트가 진행되고 있다. 외계행성 발견에 대한 소식은 언론에 자주 등장하며 일반인들도 많은 관심을 보이지만 구체적인 내용에 대한 이해는 매우 낮은 현실이다. 외계행성 탐색은 비교적 최근에 등장한 분야라 일선 학교나 일반인 대상 천문시설에서 교육프로그램으로 제대로 자리 잡지 못하고 있기도 하다. 그러므로 외계행성 탐색과 관련된 올바른 교육을 위해서 적합한 교재와 교육프로그램이 필요하다. 본 연구에서는 외계행성 탐색에 대한 교육을 위한 교재와 교육프로그램 개발 과정을 소개한다. 더불어 KMTNet과 KGMT와 같은 대형 천문 관련 프로젝트들에 대한 적절한 대국민 홍보 방안을 제안한다.심화 지구과학 교과서는 과학 계열 고등학교 학생들을 대상으로 지구과학 심화 내용에 대한 다양한 탐구 활동을 통하여 개념과 원리, 탐구 기능 창의적 문제 해결력 그리고 과학적 태도를 함양함과 동시에 대학에서 학문을 연구하는데 필요한 기본적인 능력을 기르는데 필요한 지식 및 탐구 방법을 습득할 수 있도록 실험서 형태로 내용을 구성하였다. 총 5개 대단원 중 우주 속의 지구에는 푸코진자, 시간과 역, 태양계, 달을 대상으로 한 직접 실험과 CLEA와 실제 관측 자료를 활용한 별의 일생, 성단과 변광성, 외부 은하, 그리고 허블의 법칙을 실험실에서 실습해볼 수 있도록 안내하고 있다. 2011년 8월 초판 발간으로 지금까지 20개 과학 고등학교에서 채택되어 2614명의 학생이 이용하였고, 현재 활용 실태 조사 결과를 바탕으로 수정작업이 이루어지고 있다.We present a new computational fluid dynamic (CFD) simulation code. The code employs the moving and polyhedral unstructured mesh scheme, which is known as a superior approach to the conventional SPH (smoothed particle hydrodynamics) and AMR (adaptive mesh refinement) schemes. The code first generates unstructured meshes by the Voronoi tessellation at every time step, and then solves the Riemann problem for surfaces of every Voronoi cell to update the hydrodynamic states as well as to move former generated meshes. For the second-order accuracy, the MUSCL-Hancock scheme is implemented. To increase efficiency for generating Voronoi tessellation we also develop the incremental expanding method, by which the CPU time is turned out to be just proportional to the number of particles, i.e., O(N). We will discuss the applications of our code in the context of cosmological simulations as well as numerical experiments for galaxy formation.