Revised GALEX Ultraviolet Catalog of Globular Clusters in M31Kyungsook Lee(1), Soo-Chang Rey(1), Sangmo Tony Sohn(2), and GALEX Science Team(1) Department of Astronomy and Space Science, Chungnam National University(2) Center for Space Astrophysics, Yonsei University and California Institute of Technology, USA
We present near-ultraviolet (NUV) and far-ultraviolet (FUV) photometry for the globular clusters(GCs) of M31 from mosaic images of Galaxy Evolution Explorer (GALEX). The data consist of images of 23 different 1.25 degree circular fields. Our entire survey overage is ~ 17 square degree, which includes most of disk regions currently active in forming massive stars and halo of M31. We construct UV-optical merged catalog of GCs ( and GC candidates) in M31 by cross-matching between UV photometry and optical and near-IR photometry from Revised Bolobna Catalog. The UV catalog of M31 GCs includes 510GCs and 1050 GC candidates. We explored the general UV properties and age distribution of GCs comparing with the stellar population models. We suggest UV color-color diagram has advantage of separating GCs very effectively from background galaxies and foreground stars than the case of optical color-color diagram.
GALEX UV data
GCs Separating from Galaxies
We show that the UV colors provide a useful discriminate to separate good candidate clusters from background galaxies using the large baseline provided by UV-optical colors.
Spatial centermost 3o × 3o region of the GALEX M31 mosaic. The image, a composite representation of our FUV and NUV data, has been created so as to make sources brightest in FUV appear blue and those features brightest in NUV appear orange.
(Left) 14 GALEX fields observed in 2003 and (Right) 9 additional GALEX fields observed in 2004 projected onto a 6o × 6o DSS image. Exposure times are 650 - 5100 sec. North is to the top and East is to the left.
(upper) Optical color-color diagram and (lower) UV-Optical color-color diagram for the confirmed globular clusters (open circles), confirmed star in M31 (cyan stars) and confirmed galaxies (yellow triangle).
UV-Optical Value Added Catalog
• Previous UV catalog- Rey et al. (2007)
• Updated UV catalog- UV-Optical Value Added Catalog
Age distribution of GCs in M31
(B-V) vs. (UV-V) diagrams for confirmed globular cluster (open circles), cluster candidates (cross), confirmed star in M31 (cyan stars) and confirmed galaxies (yellow triangle). We superpose our model isochrones (0.1 Gyr ~14Gyr). Not a few of cluster candidates are out of model isochrones range. They occupied area such as confirmed galaxies.
Color Distribution of M31 Cluster and Cluster Candidates
Summary & Future Works