arXiv subjects

Mun-Suk Chun

Publications and source records attributed to Mun-Suk Chun.

3 recordsLinked to original sources

arXiv2005

Discovery of Remote Star Clusters in the Halo of the Irregular Galaxy NGC 6822

We report the discovery of three new star clusters in the halo of the Local Group dwarf irregular galaxy NGC 6822. These clusters were found in the deep images taken with the MegaPrime at the CFHT, covering a total field of 2 deg x 2 deg. The most remote cluster is found to be located as far as 79 arcmin away from the center of NGC 6822. This distance is several times larger than the size of the region in NGC 6822 where star clusters were previously found. Morphological structures of the clusters and color-magnitude diagrams of the resolved stars in the clusters show that at least two of these clusters are proabably old globular clusters.

astro-ph↗

arXiv1999

Astrometric Properties of Gravitational Binary-Microlens Events and Their Applications

In this paper, we study the astrometric properties of gravitational microlensing events caused by binary lenses. By investigating the centroid shifts for various types of binary-lens events, we find that the deviations of the centroid shift trajectories from the elliptical ones of single-lens events are characterized by distortions, twistings, and big jumps. We study the conditions of binary-lens system configurations and source star trajectories for individual types of deviations. We find dramatic differences in the astrometric centroid shifts for binary-lens microlensing events that would be degenerate had their parameters been determined photometrically. Therefore, when additional astrometric observations of a binary-lens event are available, one can resolve the ambiguity of the binary-lens fit, and uniquely determine the binary-lens parameters.

astro-ph↗

arXiv1997

A Comparison of the Intrinsic Shapes of Two Different Types of Dwarf Galaxies: Blues Compact Dwarfs and Dwarf Ellipticals

We measure the apparent shapes for a sample of 62 blue compact dwarf galaxies (BCDs), and compare them with the apparent shapes for a sample of 80 dwarf elliptical galaxies (dEs). The BCDs are flatter, on average, than the dEs, but the difference is only marginally significant. We then use both non-parametric and parametric techniques to determine possible distributions of intrinsic shapes for the BCDs. The hypothesis that BCDs are oblate spheroids can be ruled out with a high confidence level ($> 99%$), but the hypothesis that they are prolate spheroids cannot be excluded. The apparent shapes of BCDs are totally consistent with the hypothesis that they are triaxial ellipsoids. If the intrinsic axis ratios, $β$ and $γ$, are distributed according to a Gaussian with means $β_0$ and $γ_0$ and standard deviation $σ$, we find the best-fitting distribution for BCDs has $(β_0,γ_0,σ)= (0.66,0.55,0.16)$, while that for dEs has $(β_0,γ_0,σ)= (0.85,0.64,0.24)$. Our results are consistent with the hypothesis that BCDs have a close evolutionary relation with dEs.

astro-ph↗