The Bulletin of The Korean Astronomical Society (천문학회보)

The Korean Astronomical Society (한국천문학회)
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Ultraviolet Color-Magnitude Relations of Early-type Dwarf Galaxies in the Viro Cluster

  • Kim, Suk (Dept. of Astronomy and Space Science, Chungnam National University) ;
  • Rey, Soo-Chang (Dept. of Astronomy and Space Science, Chungnam National University) ;
  • Sung, Eon-Chang (Korea Astronomy & Space Science Institute) ;
  • Jerjen, Helmut (Zentrum fur Astronomie der Universitat Heidelberg) ;
  • Lisker, Thorsten (Australian National University) ;
  • Lee, Youngdae (Dept. of Astronomy and Space Science, Chungnam National University) ;
  • Chung, Jiwon (Dept. of Astronomy and Space Science, Chungnam National University) ;
  • Yi, Wonhyeong (Dept. of Astronomy and Space Science, Chungnam National University) ;
  • Park, Mina (Dept. of Astronomy and Space Science, Chungnam National University)
  • Published : 2013.10.08
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Abstract

We present ultraviolet (UV) color-magnitude relations (CMRs) of early-type dwarf galaxies in the Viro cluster, combining Galaxy Evolution Explorer (GALEX) UV data with SDSS optical data, based on the Extended Virgo Cluster catalog (EVCC). We find that dwarf lenticular galaxies (dS0s) show a surprisingly distinct and tight locus separated from that of ordinary dEs, which is not clearly seen in previous CMRs. The dS0s in UV CMRs follow a steeper sequence than dEs and show bluer UV-optical color at a given magnitude. We explore the observed CMRs with population models of a luminosity-dependent delayed exponential star formation history. The observed CMR of dS0s is well matched by models with relatively long delayed star formation. The dS0s are most likely transitional objects at the stage of subsequent transformation of late-type progenitors to ordinary red dEs in the cluster environment. Most early type dwarf galaxies with blue UV colors (FUV-r < 6 and NUV-r < 4) are identified as those showing spectroscopic hints of recent or ongoing star formation activities. In any case UV photometry provides a powerful teel to disentangle the diverse subpopulations of early-type dwarf galaxies and uncover their evolutionary histories. lenticular galaxies, and irregular high surface brightness (HSB) galaxies, respectively. Dwarf elliptical galaxies and dwarf irregular LSB galaxies occupy the similar structural parameter spaces. We suggest that giant elliptical galaxies and dwarf elliptical galaxies may have different origin.

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