• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.28.1-28.1
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• 2010

Recent surveys have shown that many early-type galaxies have signatures of ongoing or recent star formation (RSF). These RSF galaxies show blue integrated UV-optical colours that set them aside in the NUV integrated colour-magnitude relation. Among them, NGC 4150 has been observed using the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope to inspect the galaxy with higher spatial resolution. In the WFC3 data, the galaxy reveals ubiquitous near-UV emission and remarkable dusty substructure. Our analysis shows this galaxy to lie in the near-UV green valley, and its pixel-by-pixel photometry exhibits a narrow range of UV-optical colours that are similar to those of nearby E+A (post-starburst) galaxies, and lie between those of M83 (an actively star-forming spiral) and the local quiescent early-type galaxy population. This work reaffirms our hypothesis that minor mergers play a significant role in the evolution of early-type galaxies at late epochs.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.539-541
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• 2015

We present a new tool for studying the spectral energy distributions (SEDs) and color-magnitude diagrams (CMDs) of galaxies and star clusters, BINARY STAR TO FIT (BS2fit). A key feature of this tool is that it takes the effects of binaries, stellar rotation and star formation history into account. It can be used to determine many parameters, including distance, extinction, binary fraction, rotational star fraction, and star formation history. Because more factors are included than in previous tools, BS2fit can potentially give new insight into the properties of galaxies and clusters. One can contact the authors for cooperation and helps via.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.74.1-74.1
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• 2019

We present the distance measurements of two spiral galaxies NGC 4517, NGC 4592, and neighboring dwarf galaxies found in Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) wide field survey data. Distances to NGC 4517 and NGC 4592 are measured by the Tip of the Red Giant Branch method from archival Hubble Space Telescope data; 9.00^+0.094_-0.260 Mpc for NGC 4517 and 8.90^+0.256_-0.060 Mpc for NGC 4592. The spatial distance between NGC 4517 and NGC 4592 is 300 kpc, which is close enough for them to be considered as a group (NGC 4517 group). Using resolved stellar photometry and Surface Brightness Fluctuation (SBF) method with HSC-SSP data, we estimate the distances to three other dwarf galaxies and confirm that they are members of the group. Velocities of three of the galaxies in the NGC 4517 group show that this group is one of the galaxy groups in the near side of the Virgo Cluster infall region.

• Journal of The Korean Astronomical Society
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• v.43 no.6
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• pp.191-200
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• 2010

We present the Korea Institute for Advanced Study Value-Added Galaxy Catalog (KIAS VAGC), a catalog of galaxies based on the Large Scale Structure (LSS) sample of New York University Value-Added Galaxy Catalog (NYU VAGC) Data Release 7. Our catalog supplements redshifts of 10,497 galaxies with 10 < $r_P\;{\leq}\;17.6$ (1455 with 10 < $r_P\;{\leq}\;14.5$) to the NYU VAGC LSS sample. Redshifts from various existing catalogs such as the Updated Zwicky Catalog, the IRAS Point Source Catalog Redshift Survey, the Third Reference Catalogue of Bright Galaxies, and the Two Degree Field Galaxy Redshift Survey have been put into the NYU VAGC photometric catalog. Our supplementation significantly improves spectroscopic completeness: the area covered by the spectroscopic sample with completeness higher than 95% increases from 2.119 to 1.737 sr. Our catalog also provides morphological types of all galaxies that are determined by the automated morphology classification scheme of Park & Choi (2005), and related parameters, together with fundamental photometry parameters supplied by the NYU VAGC. Our catalog contains matches to objects in the Max Planck for Astronomy (MPA) & Johns Hopkins University (JHU) spectrum measurements (Data Release 7). This new catalog, the KIAS VAGC, is complementary to the NYU VAGC and MPA-JHU catalog.

• Journal of The Korean Astronomical Society
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• v.51 no.4
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• pp.73-88
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• 2018

We present a sample of 54 disk galaxies which have well developed extraplanar structures. We selected them using visual inspections from the color images of the Sloan Digital Sky Survey. Since the sizes of the extraplanar structures are comparable to the disks, they are considered as prominent stellar halos rather than large bulges. A single $S{\acute{e}}rsic$ profile fitted to the surface brightness along the minor-axis of the disk shows a luminosity excess in the central regions for the majority of sample galaxies. This central excess is considered to be caused by the central bulge component. The mean $S{\acute{e}}rsic$ index of the single component model is $1.1{\pm}0.9$. A double $S{\acute{e}}rsic$ profile model that employs n = 1 for the inner region, and varying n for the outer region, provides a better fit than the single $S{\acute{e}}rsic$ profile model. For a small fraction of galaxies, a $S{\acute{e}}rsic$ profile fitted with n = 4 for the inner region gives similar results. There is a weak tendency of increasing n with increasing luminosity and central velocity dispersion, but there is no dependence on the local background density.

• The Bulletin of The Korean Astronomical Society
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• v.24 no.1
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• pp.43-43
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• 1999

• The Bulletin of The Korean Astronomical Society
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• v.7
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• pp.4.3-5
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• 1982

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.57.2-57.2
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• 2011

Recent studies find that some early-type galaxies host Type II or Ibc supernovae (SNe II, Ibc). This may imply recent star formation activities in these SNe host galaxies, but a massive star origin of the SNe Ib so far observed in early-type galaxies has been questioned because of their intrinsic faintness and unusually strong Ca lines shown in the nebular phase. To address the issue, we investigate the properties of early-type SNe host galaxies using the data with Galaxy Evolution Explorer (GALEX) ultraviolet photometry and the Sloan Digital Sky Survey optical data. Our sample includes eight SNe II and one peculiar SN Ib (SN 2000ds) host galaxies as well as 32 SN Ia host galaxies. The host galaxy of SN 2005cz, another peculiar SN Ib, is also analyzed using the GALEX data and the NASA/IPAC Extragalactic Database optical data. We find that the NUV?optical colors of SN II/Ib host galaxies are systematically bluer than those of SN Ia host galaxies, and some SN II/Ib host galaxies with NUV - r colors markedly bluer than the others exhibit strong radio emission. We perform a stellar population synthesis analysis and find a clear signature of recent star formation activities in most of the SN II/Ib host galaxies. Our results generally support the association of the SNe II/Ib hosted in early-type galaxies with core collapse of massive stars. We briefly discuss implications for the progenitors of the peculiar SNe Ib 2000ds and 2005cz.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.47.2-47.2
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• 2013

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.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.145-146
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• 2012

We present the results from B-, R-, I-, J- and H-band observations of the NEP-Wide survey field. The NEP-Wide survey is an AKARI survey of the North Ecliptic Pole covering ~ 5 square degrees area. Our optical/NIR imaging supports the AKARI IR imaging data by providing a crucial coverage in the optical/NIR. The optical data were obtained in 2007 using the 1.5 m telescope and SNUCAM at Maidanak Observatory, Uzbekistan. The NIR data were obtained in 2008 with FLAMINGOS on the KPNO 2.1 m telescope. We used IRAF, SExtractor, SCAMP, and SWarp for reducing the raw data, I-band fringe pattern removal, astrometry, standard photometry calibration, and source detection. Our optical-NIR data reach the depths of B ~ 23.4, R ~ 23.1, I ~ 22.3, J ~ 21.05, and H ~ 20.64 AB mag at 5-sigma. Here, we present the astrometric accuracy, galaxy number counts, completeness, and reliability, as well as redshift tracks of some normal galaxies and quasars on the B - R vs. R - I color-color diagram. The photometric data are being used for identifying optical counterparts of the IR data provided by AKARI, studying their SEDs, and selecting interesting objects for spectroscopic follow-up studies.