Probing the Intermediate-Age Globular Clusters in NGC 5128 from Ultraviolet Observations
Abstract
We explore the age distribution of the globular cluster (GC) system of the nearby elliptical galaxy NGC 5128 using ultraviolet (UV) photometry from Galaxy Evolution Explorer (GALEX) observations, with UV - optical colors used as the age indicator. Most GCs in NGC 5128 follow the general trends of GCs in M31 and Milky Way in UV - optical color-color diagram, which indicates that the majority of GCs in NGC 5128 are old similar to the age range of old GCs in M31 and Milky Way. A large fraction of spectroscopically identified intermediate-age GC (IAGC) candidates with ~ 3-8 Gyr are not detected in the FUV passband. Considering the nature of intermediate-age populations being faint in the far-UV (FUV) passband, we suggest that many of the spectroscopically identified IAGCs may be truly intermediate in age. This is in contrast to the case of M31 where a large fraction of spectroscopically suggested IAGCs are detected in FUV and therefore may not be genuine IAGCs but rather older GCs with developed blue horizontal branch stars. Our UV photometry strengthens the results previously suggesting the presence of GC and stellar subpopulation with intermediate age in NGC 5128. The existence of IAGCs strongly indicates the occurrence of at least one more major star formation episode after a starburst at high redshift.
Keywords
Cite
@article{arxiv.0906.2602,
title = {Probing the Intermediate-Age Globular Clusters in NGC 5128 from Ultraviolet Observations},
author = {Soo-Chang Rey and Sangmo T. Sohn and Michael A. Beasley and Young-Wook Lee and R. Michael Rich and Suk-Jin Yoon and Sukyoung K. Yi and Luciana Bianch and Yongbeom Kang and Kyeongsook Lee and Chul Chung and Tom A. Barlow and Karl Foster and Peter G. Friedman and D. Christopher Martin and Patrick Morrissey and Susan G. Neff and David Schiminovich and Mark Seibert and Ted K. Wyder and Jose Donas and Timothy M. Heckman and Barry F. Madore and Bruno Milliard and Alex S. Szalay and Barry Y. Welsh},
journal= {arXiv preprint arXiv:0906.2602},
year = {2009}
}
Comments
8 pages, 3 figures, accepted for ApJ Letter