• 천문학회보
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• 제35권1호
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• pp.56.2-56.2
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• 2010

M87, a cD galaxy in the Virgo cluster, has 3-10 times larger enclosed mass than the Milky Way at any given galactocentric radius. Thus the globular cluster (GC) system in M87 is expected to have undergone a more significant dynamical evolution than that of the Milky Way if it had started from the same initial mass function (MF) and radial distribution (RD) as the Milky Way. The evolution of MF and RD of the M87 GC system has been calculated using an advanced, realistic Fokker-Planck (FP) model that considers dynamical friction, disk/bulge shocks, and eccentric cluster orbits. We perform hundreds of FP calculations with different initial cluster conditions, and then search a wide parameter space for the best-fit initial GC MF and RD that evolves into the observed present-day GC MF and RD. We also find best-fit initial MFs and RDs for blue and red GC groups, separately.

• 천문학회보
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• 제39권1호
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• pp.47.1-47.1
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• 2014

We examine the effect of environment on star formation activity of a sample of galaxy group catalogue given in Tempel et al.(2012) constructed from the Sloan Digital Sky Survey Data Release 8. In order to compare galaxies in different environment, we classify galaxies into two groups: galaxies in low density environment and galaxies in high density environment. After matching colors and apparent magnitudes of the galaxies, we are left with 5912 galaxies in each of the environment category. The fraction of star-forming galaxies in low-density environment is ~34%, higher than ~15% in high-density environment. Star-forming galaxies in low density environment have a higher average SFR value than those in high density environment. The bulge-to-disk ratio for galaxies in two different environment shows bimodal distribution. Regardless of the environment, we find galaxies with high star formation rate despite their red (g-r) color, for which the origin enhancing their star formation rate is investigated.

• 천문학논총
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• 제30권2호
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• pp.465-467
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• 2015

We presents a study of interactions between galaxies in the low-redshift group known as the NGC 4065 group. Imaging data were taken using the 2.4 meter telescope at the Thai National Observatory (TNO) for B, V and $R_c$ broadband filters and [$S\small{II}$] and Red-continuum narrowband filters. There are 21 galaxies in our sample. The results show that most early type galaxies (ETGs) with equivalent width EW($H{\alpha}$) < $10{\AA}$ are gas-deficient galaxies, while late type galaxies (LTGs) show more EW($H{\alpha}$) and are bluer than the ETGs. This means that star formation activity in the LTGs could be triggered by tidal interactions between galaxy members due to dense environmental effects in the compact group.

• 천문학회보
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• 제46권2호
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• pp.67.2-67.2
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• 2021

We present preliminary results on the chemical and kinematic analysis of accreted and heated metal-rich (-1.0 < [Fe/H] < -0.3) stars in the Galactic disk. These stars are in the ranges of e > 0.7, -100 < V_𝜙 < 100 km/s, and |Z| < 3 kpc, and are presumably heated (accreted) by (from) past merger events such as Gaia Enceladus and Sausage (GSE). These stars are largely separated into two groups based on the level of [α/Fe] and radial velocity dispersion. The first group has low [α/Fe] and high radial velocity dispersion, and the second group shows high [α/Fe] and low radial velocity dispersion. We propose that the first group of stars are accreted from the GSE galaxy, whereas the second group of stars are dynamically heated by the GSE merger event.

• 천문학회보
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• 제46권1호
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• pp.30.2-30.2
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• 2021

The extended Lyα nebulae (also known as Lyα blobs or LABs) observed at z=2-6 can provide clues to galaxy formation in the early universe. The connection of LABs with the overdensities of compact Lyα emitters suggests that they are associated with matter density peaks in the universe and thus likely to evolve into the present-day groups and clusters of galaxies. However, the mechanism powering the extended Lyα emission in LABs is remained controversial. The detection of polarization signals that follow the theoretically predicted trend is interpreted as strong evidence supporting that the LABs are caused primarily by the resonance scattering of Lyα originating from star-forming galaxies and AGNs. However, Trebitsch et al. (2016) claimed that the radial profile of polarization could be better explained by the scenario in which Lyα photons are produced in the cooling gas surrounding galaxies and then self-scattered by the gas, rather than by the scattering scenario of photons originating from the central galaxies. In this presentation, using LaRT, a state-of-art Lyα radiative transfer code, it is demonstrated that the observed polarization pattern can be reproduced even with the scattering scenario.

• Clinics in Shoulder and Elbow
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• 제26권1호
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• pp.64-70
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• 2023

Background: This study aimed to analyze the efficacy of single-dose corticosteroid injection (CSI) administered at 6 weeks postoperative to treat stiffness following arthroscopic rotator cuff repair (ARCR). Methods: In this prospective, multicentric, case-control study, post-ARCR stiffness at 6 weeks was treated with either a single dose of intra-articular CSI (CSI group) or physical therapy with oral analgesics (non-CSI group). Pain intensity according to visual analog scale (VAS), functional outcome using the Constant Murley Shoulder Score, time to return to activities of daily living (ADLs), and retear rate were recorded at 6 weeks, 9 weeks, 12 weeks, 6 months, 12 months, and 18 months postoperatively in both groups. Results: A total of 149 patients (54.5%) in the CSI group and 124 patients (45.5%) in the non-CSI group were included in this study. Pain and function were significantly better in the CSI group at 9-week, 12-week, and 6-month (P<0.001) follow-up, whereas they were not significantly different when the groups were compared at 12- and 18-month follow-up. The mean duration to return to ADLs was significantly shorter (P<0.001) in the CSI group. The incidence of retears was not significantly different (P=0.36) between groups at the end of 18 months of follow-up. Conclusions: Single-dose intra-articular CSI administered at 6 weeks postoperative to treat post-ARCR stiffness significantly improved pain, function, and duration of return to ADLs without increasing the risk of retears compared to patients who did not receive intra-articular CSI. Level of evidence: III.

• 대한지구과학교육학회지
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• 제4권2호
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• pp.151-165
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• 2011

Following a microgenetic design, this study was analysed the characteristic and the change of classification strategy that appear in college students' classification activity. The 4 tasks were developed for classification activity; a shell as a familiar real things, an animal fossil as a unfamiliar real things, a snow flake as a familiar picture cards and galaxy as a unfamiliar picture card. Achieved study to 6 college students who major in elementary education. Data were collected by interview with subjects, subject's classification schema, investigator's observation of subject's activity, and videotaped that record subject's subject classification process over an extended period of 6 times. Result proved in this study is as following. In the 6 times of the data collection procedures, a strategy F identifying concrete attribution of classification objects and a more detailed strategy X3 combining qualitative, spatial and dimensional attribution were found and more frequently used in both groups of college students which reported a classification process and did not report the process. While discovery and absorption of both a concrete classification strategy and a detailed classification strategy were rapidly developed in the reporting group, they were gradually developed in the non-reporting group. In addition to this, as the data collection procedures were progressing, the college students were familiar with change factors of classification tasks and in the case of pictures the classification strategy showed more desirable changes.

• 천문학회보
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• 제38권2호
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• pp.41.2-41.2
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• 2013

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.

• 천문학회보
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• 제39권2호
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• pp.56.2-56.2
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• 2014

We present an extensive study of the environment of galaxies with bars in the low-redshift Uni-verse, using a volume-limited sample of over 30,000 galaxies drawn from the Sloan Digital Sky Survey, with visually-determined morphological classifications and bar identifications. We use four different statistics to quantify the environment of our galaxies: the projected two-point cross-correlation function with respect to a spectroscopic sample of reference galaxies, the background-subtracted number count of galaxies in a deep photometric sample in the vicinity of our galaxies, the overdensity of the local environment estimated at ~3 Mpc scale from the three-dimensional reconstruction of the cosmic density field of the local Universe, and the membership of our galaxies in the SDSS galaxy groups to segregate central to satellite systems. We find a weak, but significant trend for early-type galaxies with a bar to be more strongly clustered on scales from a few 100 kpc to 1 Mpc, when compared to early-type galaxies without a bar. For late-type galaxies, we find less neighbours within ~50 kpc around the barred late-types when compared to the unbarred late-types. For late-type galaxies we also detect a decrease of the bar fraction for dark matter dominated systems, and finally we find no obvious correlation between the overdensity and the fraction of barred galaxies in our sample.

• 천문학논총
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• 제21권2호
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• pp.21-26
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• 2006

A Korean team (Korea Astronomy and Space Science Institute, Korea Basic Science Institute, and Kyung Hee University) takes part in an international cooperation project called CIBER (Cosmic Infrared Background ExpeRiment), which has begun with Jet Propulsion Laboratory (JPL) in USA and Institute of Space and Astronautical Science (ISAS) in Japan. CIBER is a rocket-borne instrument, of which the scientific goal is to measure the cosmic near-infrared extra-galactic background to search for signatures of primordial galaxy formation. CIBER consists of a wide-field two-color camera, a low-resolution absolute spectrometer, and a high-resolution narrow-band imaging spectrometer. The Korean team is in charge of the ground support electronics and manufacturing of optical parts of the narrow-band spectrometer, which will provide excellent opportunities for science and technology to Korean infrared groups.