• 천문학회보
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• 제35권2호
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• pp.28.2-28.2
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• 2010

We investigate star clusters in the Stephan's Quintet using Wide Field Camera 3 of the Hubble Space Telescope and three filters (F438W, F606W, F814W). Stephan's Quintet located at ~ 85 Mpc, so most star clusters are seen like point source even in HST image. We perform the Point Spread Funtion fitting photometry to find star clusters. Then we have selected 749 star cluster candidates by visual inspection. Usinng simple steallr population models (Bruzual & Charlot, 2003), we estimate ages of these star clusters. Many young star clusters found in tidal features of NGC 7318 and NGC 7319. Also star clusters in the shocked region of NGC7318 have younger age than those in NGC 7319 tidal tail. These result implies interaction which distrupt NGC 7319 first, and collision between NGC 7318 A/B occurred. In contrast, old star clusters are mainly located in NGC 7317 and in the center of other galaxies. Implications of these result will be discussed.

• 천문학회보
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• 제39권1호
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• pp.39.2-39.2
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• 2014

We present a photometric study of star clusters in the nuclear starburst region of NGC 253 using gVI, YJ, and H band images in the Hubble Space Telescope archive. We find about one thousand star clusters in about 200"x200" field by visual inspection with I<21. We also find about ten thousand star clusters in the same field by automated classification method with magnitude range of 21< I $$\leq_-$$ 24. Ages and masses of star clusters are estimated using spectral energy distribution fitting method. Age distribution of star cluster shows two distinguished young populations with peak ages at 3.5 Myr and 18 Myr. Old populations (>100 Myr) are exist, but their number is small. About thirty young massive star clusters (<10 Myr, ) are found in nuclear region of NGC 253 which are regarded as a result of the recent starburst. Mass function of young star clusters in NGC 253 is somewhat different with those of star clusters in other galaxies. This result suggests that initial cluster mass functions (ICMFs) for star clusters are not universial. Especially ICMF in starburst galaxies may be distinguishable compared with those in normal spiral galaxies. We discuss the implications of these results.

• 천문학회보
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• 제36권2호
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• pp.144.2-144.2
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• 2011

A dwarf irregular galaxy IC10 in the Local Group is the nearest starburst galaxy, playing an important role revealing the details of starburst. It is located close to the Galactic plane so that it suffers from severe foreground reddening. Therefore much less is known about the property of this galaxy compared with other galaxies in the Local Group. So are star clusters in this galaxy. We present a photometric study of the star clusters in IC10. 57 star clusters are already found from HST images in previous studies, and we newly found 15 star clusters using Local Group Survey data and SUBARU/Suprime-Cam data. We derive UBVRI integrated photometry of these star clusters from the images from Local Group Survey data and JHKs photometry taken with SUBARU/MOIRCS. Then we derive age and mass of these clusters using the spectral energy distribution fitting with the simple stellar population models. We discuss the photometric and physical properties of these star clusters and its implication.

• 천문학회보
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• 제36권1호
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• pp.63.2-63.2
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• 2011

We present a photometric study of star clusters in three nearby barred spiral galaxies NGC 1300, NGC 1672 and NGC 6217. We use the Hubble Heritage CCD images taken with Advanced Camera for Surveys (ACS) of Hubble Space Telescope (HST) in several filters. We have selected hundreds of star clusters with V $\leq$ 24 mag in each galaxy, based on the morphological parameters and visual inspection. Most of the blue star clusters with B-V $\leq$ 0.5 are strongly concentrated in spiral arms. A significant fraction of these star clusters are distributed in ansae (the joint between spiral arms and bar structure). Some of the blue star clusters are also found in the nuclear starburst region, especially in NGC 1672. A small number of star clusters are found in the bar region. In contrast, the red star clusters with B-V < 0.5 are relatively uniformly located over the entire field of galaxy, and show some central concentration around the bulge. We discuss the physical properties of these star clusters with the expected results from simulations.

• 천문학회지
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• 제43권1호
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• pp.1-8
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• 2010

JHK near-infrared photometry of star clusters in the dwarf irregular/dwarf starburst galaxy NGC 1569 are presented. After adopting several criteria to exclude other sources (foreground stars, background galaxies, etc.), 154 candidates of star clusters are identified in the near-infrared images of NGC 1569, which include very young star clusters. Especially, from analysis based on theoretical background, we found ten very young star clusters near the center of NGC 1569. The total reddening values toward these clusters are estimated to be $A_V$=1-9 mag from comparison with the theoretical estimates given by the Leitherer et al. (1999)'s star cluster model.

• 천문학회보
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• 제37권1호
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• pp.57.2-57.2
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• 2012

We present a survey for finding hidden star clusters using the WISE data. There are more than two thousand star clusters in the current catalogs of star clusters in the Milky Way Galaxy. However, there are still numerous star clusters remaining to be discovered, especially, along the Milky Way. The WISE, NIR to MIR all sky survey, is an efficient source to find star clusters obscured by dust along the Milky Way. Taking the advantage of the power of WISE, we survey a wide area at ${\mid}l{\mid}<30^{\circ}$ and ${\mid}b{\mid}<6^{\circ}$, toward to the central region of the Milky Way to find new star clusters. To find cluster candidates, we used two kinds of method: the visual inspection and the brightness density investigation. We will report the progress of this survey.

• 천문학회지
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• 제39권4호
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• pp.89-94
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• 2006

We present JHK-band near-infrared photometry of the star clusters in the dwarf irregular galaxy IC 5152. After excluding possible foreground stars, a number of candidate star clusters are identified in the near-infrared images of IC 5152, which include young populations. Especially, five young star clusters are identified in the(J-H, H-K) two color diagram and the total extinction values toward these clusters are estimated to be $A_v=2-6$ from the comparison with the theoretical values given by the Leitherer et al.(1999)'s theoretical star cluster model.

• 천문학회보
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• 제36권2호
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• pp.78.1-78.1
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• 2011

We report on a photometric study of star clusters in the circumnuclear star-forming region of nearby barred spiral galaxy NGC 1672. We use FUV to NIR imaging data (FUV, U, B, V, R, $H{\alpha}$, I, and H) in the Hubble Space Telescope (HST) archive. We have selected 89 star clusters with V<21.8 (MV<-9) mag in the central 600 pc region, and have derived their age & mass by comparing their colors with theoretical population synthesis models. Most of the star clusters are mildly reddened (E(B-V)~0.2 on average), but some star clusters suffer from severe reddening (E(B-V)>0.6). The mass of the star clusters are in the range from $10^4\;M_{\odot}$ to $10^7\;M_{\odot}$. About half of them are more massive than $10^5\;M_{\odot}$. Their ages range from 1 Myr to several 100 Myr, and concentrate at ~6 Myr and ~40 Myr. It indicates that the episodic starburst in the circumnuclear star-forming region lasted at least several 100 Myr. We find no obvious azimuthal age gradient, but we find a radial age gradient in some regions. We discuss these properties with theoretical expectations.

• 천문학회보
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• 제35권1호
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• pp.56.1-56.1
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• 2010

We present JHK photometry of star clusters in the dwarf irregular/dwarf starburst galaxy NGC 1569. Adopting several criteria to exclude other sources like foreground stars, background galaxies, etc., ~150 star cluster candidates are identified in the near-infrared images of NGC 1569, which include very young star clusters. From analysis based on theoretical background, we find ten very young star clusters near the center of this galaxy. The total reddening values toward these clusters are estimated from comparison with the theoretical estimates given by star cluster mode.

• 천문학회보
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• 제46권1호
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• pp.52.3-53
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• 2021

It is yet to be understood what controls the star formation activity in high-redshift galaxy clusters. One recently proposed mechanism is that the star formation activity in galaxy clusters are fed by gas and galaxies in large-scale structures surrounding them, which we call as "web feeding model". Using galaxies in the COSMOS2015 catalog, with mass completeness at log(M/M_⦿)≥9.54 and reliable photometric redshift data (σ_Δz/(1+z) ≲ 0.01), we study the star formation activities of galaxy clusters and their surrounding environment to test the web feeding model. We first identify the overdense regions with number density exceeding the 4σ-level from photometric redshift data as galaxy clusters, and we find that they are well matched with clusters identified in the X-ray extended source catalog. Furthermore, we identify galaxy large scale structures, and will present the correlation or anti-correlation between quiescent galaxy fraction, an indicator of star-forming activity, and the prevalence of galaxy large scale structures.