Sang-Gak Lee

STELLAR MASSES FROM THE CANDELS SURVEY: THE GOODS-SOUTH AND UDS FIELDS

We present the public release of the stellar mass catalogs for the GOODS-S and UDS fields obtained using some of the deepest near-IR images available, achieved as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey project. We combine the effort from 10 different teams, who computed the stellar masses using the same photometry and the same redshifts. Each team adopted their preferred fitting code, assumptions, priors, and parameter grid. The combination of results using the same underlying stellar isochrones reduces the systematics associated with the fitting code and other choices. Thanks to the availability of different estimates, we can test the effect of some specific parameters and assumptions on the stellar mass estimate. The choice of the stellar isochrone library turns out to have the largest effect on the galaxy stellar mass estimates, resulting in the largest distributions around the median value (with a semi interquartile range larger than 0.1 dex). On the other hand, for most galaxies, the stellar mass estimates are relatively insensitive to the different parameterizations of the star formation history. The inclusion of nebular emission in the model spectra does not have a significant impact for the majority of galaxies (less than a factor of 2 for ~80% of the sample). Nevertheless, the stellar mass for the subsample of young galaxies (age <100 Myr), especially in particular redshift ranges (e.g., 2.2 < z < 2.4, 3.2 < z < 3.6, and 5.5 < z < 6.5), can be seriously overestimated (by up to a factor of 10 for <20 Myr sources) if nebular contribution is ignored.

The Open Cluster NGC 2516. I. Optical Photometry

We present UBVI CCD photometry of the intermediate-age open cluster NGC 2516. From this new photometry we derive the cluster parameters [V0 - MV = 7.77 ± 0.11 mag, E(B-V) = 0.112 ± 0.024 mag], age [log (age) = 8.2 ± 0.1], and a photometric abundance ([Fe/H] = -0.10 ± 0.04) from a comparison with theoretical isochrones of the Padua group. We find that the X-ray bright stars [log LX(ergs s-1)29.0] are systematically bluer in B-V and U-B. It was necessary to modify the photometric membership criterion used by Sung & Bessell due to the UV excess of X-ray bright stars and due to the abrupt increase in the slope of the (MV, B-V) ZAMS relation at B-V1.4. A minimum binary frequency 40% (±5%) was estimated from the distribution of distance moduli of unevolved photometric members. The photometric abundance obtained in this study is similar to that of the Pleiades and therefore the lower metallicity is not the cause of strong X-ray emission of F-type stars in NGC 2516. We believe that this results from them being close binaries, as suggested by their different distribution of distance moduli compared to other cluster members and surmise that the tidal forces between the two stars must increase their X-ray activity.

THE GLOBULAR CLUSTER SYSTEM OF M60 (NGC 4649). II. KINEMATICS OF THE GLOBULAR CLUSTER SYSTEM

We present a kinematic analysis of the globular cluster (GC) system in the giant elliptical galaxy (gE) M60 in the Virgo Cluster, using a photometric and spectroscopic database of 121 GCs (83 blue and 38 red GCs). We have found that the M60 GC system shows a significant overall rotation. The rotation amplitude of the blue GCs is slightly smaller than or similar to that of the red GCs, and the position angles of their rotation axes are similar. The velocity dispersions about the mean velocity and about the best-fit rotation curve for the red GCs are marginally larger than those for the blue GCs. Comparison of observed stellar and GC velocity dispersion profiles with those calculated from the stellar mass profile shows that the mass-to-light ratio should increase as the galactocentric distance increases, indicating the existence of an extended dark matter halo. The sample of all the GCs in M60 is found to have a tangentially biased velocity ellipsoid, unlike the GC systems in other gEs. The two subsamples appear to have different velocity ellipsoids. The blue GC system has a modestly tangentially biased velocity ellipsoid, while the red GC system has a modestly radially biased or an isotropic velocity ellipsoid. We compare the kinematic properties of the M60 GC system to those of other gEs (M87, M49, NGC 1399, NGC 5128, and NGC 4636), and discuss the implication of these results for the formation models of the GC system in gEs.

ABUNDANCES OF REFRACTORY ELEMENTS FOR G-TYPE STARS WITH EXTRASOLAR PLANETS

We confirm the difference in chemical abundance between stars with and without exoplanets and present the relation between chemical abundances and physical properties of exoplanets, such as planetary mass and the semimajor axis of planetary orbit. We obtained the spectra of 52 G-type stars from the Bohyunsan Optical Astronomy Observatory (BOAO) Echelle Spectrograph and carried out abundance analyses for 12 elements: Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, and Ni. We first found that the [Mn/Fe] ratios of planet-host stars are higher than those of comparison stars over the entire metallicity range, and we then found that in metal-poor stars of [Fe/H] < –0.4 the abundance difference was larger than in metal-rich samples, especially for the elements of Mg, Al, Sc, Ti, V, and Co. After examining the relation between planet properties and metallicities of planet-host stars, we observed that planet-host stars with low metallicities tend to have several low-mass planets (

The Relation between Near-infrared Luminosity of Red Giant Branch Bumps and Metallicity of Galactic Globular Clusters

Using photometric data from the Two Micron All Sky Survey Second Incremental Release Point Source Catalog, we constructed Ks versus J-Ks color-magnitude diagrams (CMDs) of Galactic globular clusters (GGCs) for which the JKs photometric data have been made available up to now. On the CMDs of 13 GGCs, we identified red giant branch bump features and derived luminosities of bumps in Ks (K) and in M (M) for 11 of them. We reconfirm the relation between M and metallicity [Fe/H]CG97 or [M/H], such that the luminosity of bump becomes brighter as metallicity [Fe/H]CG97 or [M/H] decreases. This result is similar to that obtained by Ferraro et al. (published in 1999) for the relation between M and [M/H] based on observations of 47 GGCs that were conducted in the optical region (V vs. B-V CMDs). Our results show the same trend as those found by Ferraro et al. (published in 2000) for the relations between M and metallicity [Fe/H]CG97 and [M/H] derived from observations of eight GGCs in the same near-infrared region (K vs. J-K CMDs). Combining with the 2000 data of Ferraro et al., we derive a robust relation for the metal-dependent luminosities of the bumps.

Tool for Automatic Measurement of Equivalent width (TAME)

We present a tool for measuring the equivalent width (EW) in high-resolution spectra. The Tool for Automatic Measurement of Equivalent width (tame) provides the EWs of spectral lines by profile fitting in an automatic or interactive mode, which can yield a more precise result through the adjustment of the local continuum and fitting parameters. The automatic EW results of tame have been verified by comparing them with the manual EW measurements by the iraf splot task using the high-resolution spectrum of the Sun and measuring EWs in the synthetic spectra with different spectral resolutions and signal-to-noise (S/N) ratios. The EWs measured by tame agree well with the manually measured values, with a dispersion of less than 2 mA. By comparing the input EWs for synthetic spectra and EWs measured by tame, we conclude that it is reliable for measuring the EWs in a spectrum with a spectral resolution of R ≳ 20 000 and find that the errors in EWs are less than 1 mA for an S/N ratio ≳100.

Wide-Field Stellar Distributions around the Remote Young Galactic Globular Clusters Palomar 3 and Palomar 4*

In a search for tidal extension features and/or streams of the probable parent satellite galaxies around the remote young globular clusters Pal 3 and Pal 4, we used wide-field VI photometry of an area a ~ 13 × 13 around Pal 3 and an area a ~ 13 × 09 around Pal 4, obtained with the CFH12K mosaic CCD. Applying the CMD-mask algorithm to stars in the vicinity of the clusters, we selected member star candidates that were used to examine the characteristics of the spatial distribution of stars around Pal 3 and Pal 4. The isodensity contours in the Gaussian-smoothed spatial stellar density maps around the clusters, and the Kolmogorov-Smirnov test applied to the corresponding luminosity functions, indicate tidal halos around Pal 3 at distances of up to ~4rt, and around Pal 4 of up to ~6rt. The stellar distribution around Pal 3 suggests north-south elongations along the directions of the Galactic center and anticenter, and a northeast extension in the direction of the clusters proper motion. In the vicinity of Pal 4 an extension of a tail around the cluster in the opposite direction to the Galactic center and a possible extension of stars toward the Galactic center have also been detected in the isodensity maps and in the angular luminosity functions. We discuss the relevance of the spatial distribution of stars in possible streams around Pal 3 and Pal 4 to these spatial correlations and to the space orbits of the possible parent satellite galaxies.

NEAR-IR PHOTOMETRIC STUDY OF THE FU ORIONIS OBJECT HBC 722

We present near-infrared light curves of HBC 722 after its the September 2010 outburst. We have been monitoring its near-infrared light curves since November 2010 with Korean Astronomy and Space Science Institute Infrared Camera System (KASINICS). HBC 722 exhibits large changes in optical and near-infrared brightness since its outburst. The J, H, and Ks light curves over about 2.5 years show that in all observed bands HBC 722 progressively became fainter until around April 2011, down to J �10.7, H �9.9, Ks �9.3, but it is getting brighter again. Large scatter in the obtained light curve prevents us from finding whether there is any short timescale variation as reported in other optical observations. The near-infrared color of HBC 722 is becoming bluer since its outburst. The pre-outburst Spectral Energy Distribution (SED) of HBC 722 is consistent with that of a slightly reddened Class II YSO with the exception of the extraordinary IR-excess in the far-infrared region.

HIGH RESOLUTION OPTICAL AND NIR SPECTRA OF HBC 722

We present the results of high resolution (R

HIGH RESOLUTION OPTICAL SPECTRA OF HBC 722 AFTER OUTBURST

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