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A Search for Young Stars in the S0 Galaxies of a Super-Group at z=0.37
The Astrophysical Journal
  • Dennis W. Just, University of Arizona
  • Dennis Zaritsky, University of Arizona
  • Kim-Vy H. Tran, Texas A&M University; University of Zürich
  • Anthony H. Gonzalez, University of Florida
  • Stefan Kautsch, Nova Southeastern University
  • John Moustakas, University of California - San Diego
Publication Date
  • Galaxies: clusters: general,
  • Galaxies: evolution,
  • Galaxies: photometry,
  • Methods: observational
We analyze Galaxy Evolution Explorer UV data for a system of four gravitationally bound groups at z = 0.37, SG1120, which is destined to merge into a Coma-mass cluster by z = 0, to study how galaxy properties may change during cluster assembly. Of the 38 visually classified S0 galaxies, with masses ranging from log (M *)[M ☉] ≈ 10-11, we detect only one in the near-UV (NUV) channel, a strongly star-forming S0 that is the brightest UV source with a measured redshift placing it in SG1120. Stacking the undetected S0 galaxies (which generally lie on or near the optical red sequence of SG1120) still results in no NUV/far-UV (FUV) detection (<2σ). Using our limit in the NUV band, we conclude that for a rapidly truncating star formation rate, star formation ceased at least ~0.1-0.7 Gyr ago, depending on the strength of the starburst prior to truncation. With an exponentially declining star formation history over a range of timescales, we rule out recent star formation over a wide range of ages. We conclude that if S0 formation involves significant star formation, it occurred well before the groups were in this current pre-assembly phase. As such, it seems that S0 formation is even more likely to be predominantly occurring outside of the cluster environment.

©2011. The American Astronomical Society. All rights reserved.

Additional Comments
Support from JPL/Caltech GO program #20683; NASA LTSA award # NNG05GE82G; GALEX grant #MMX11AI47G; NASA/HST/G0-10499; JPL/Caltech SST GO-20683; Swiss National Science Foundation grant # PP002-110576
Citation Information
Dennis W. Just, Dennis Zaritsky, Kim-Vy H. Tran, Anthony H. Gonzalez, et al.. "A Search for Young Stars in the S0 Galaxies of a Super-Group at z=0.37" The Astrophysical Journal Vol. 740 Iss. 2 (2011) p. 1 - 6 ISSN: 0004-637X
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