A SEARCH FOR YOUNG STARS IN THE S0 GALAXIES OF A SUPER-GROUP AT z = 0.37
- Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
- George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics, Texas A and M University, College Station, TX 77843 (United States)
- Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055 (United States)
- Department of Physics, Computer Science and Engineering, Christopher Newport University, Newport News, VA 23606 (United States)
- Center for Astrophysics and Space Sciences, University of California, San Diego, La Jolla, CA 92093 (United States)
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{sub *})[M{sub sun}] {approx} 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 (<2{sigma}). Using our limit in the NUV band, we conclude that for a rapidly truncating star formation rate, star formation ceased at least {approx}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.
- OSTI ID:
- 21587391
- Journal Information:
- Astrophysical Journal, Vol. 740, Issue 2; Other Information: DOI: 10.1088/0004-637X/740/2/54; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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