Ultra-Compact Dwarf Candidates Near the Lensing Galaxy in Abell S0740
John P. Blakeslee, Regina Barber DeGraaff

TL;DR
This study identifies and analyzes 15 ultra-compact dwarf galaxy candidates near the lensing galaxy ESO325-G004 using HST imaging, revealing potential differences in formation mechanisms and their relation to globular clusters.
Contribution
First detailed analysis of UCD candidates around the nearest strong lensing galaxy, using size, color, and halo features to explore their nature and origins.
Findings
15 UCD candidates identified within the ACS field.
Size distribution suggests different formation mechanisms.
UCDs follow the distribution of globular clusters and galaxy halo light.
Abstract
We analyze three-band HST/ACS imaging data of the giant elliptical galaxy ESO325-G004. This is the nearest known strongly lensing galaxy, and it resides in the center of the poor cluster Abell S0740 at redshift z=0.034. Based on magnitude, color, and size selection criteria, we identify a sample of 15 ultra-compact dwarf (UCD) galaxy candidates within the ACS field. This is comparable to the numbers of UCDs found within similar regions in more nearby clusters (Virgo, Fornax, Hydra). We estimate circular half-light radii R_e,c from 2-D Sersic and King model fits and apply an upper cutoff of 100pc for our UCD selection. The selected galaxies have typical Sersic indices , while larger sources with R_e,c > 100pc are more nearly exponential, perhaps indicating that the latter are dominated by background disk galaxies. Many of the UCD candidates are surrounded by a faint "fuzz"…
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