Moran, Sean M. and Ellis, Richard S. and Treu, Tommaso and Smith, Graham P. and Rich, R. Michael and Smail, Ian (2007) A Wide-Field Survey of Two z ~ 0.5 Galaxy Clusters: Identifying the Physical Processes Responsible for the Observed Transformation of Spirals into S0s. Astrophysical Journal, 671 (2). pp. 1503-1522. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20100223-085949266
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We present new results from our comparative survey of two massive, intermediate-redshift galaxy clusters, Cl 0024+17 (z = 0.39) and MS 0451–03 (z = 0.54). Combining optical and UV imaging with spectroscopy of member galaxies, we identify and study several key classes of "transition objects" whose stellar populations or dynamical states indicate a recent change in morphology and star formation rate. For the first time, we have been able to conclusively identify spiral galaxies in the process of transforming into S0 galaxies. This has been accomplished by locating both spirals whose star formation is being quenched and their eventual successors, the recently created S0s. Differences between the two clusters in both the timescales and spatial location of this conversion process allow us to evaluate the relative importance of several proposed physical mechanisms that could be responsible for the transformation. Combined with other diagnostics that are sensitive to either ICM-driven galaxy evolution or galaxy-galaxy interactions, we describe a self-consistent picture of galaxy evolution in clusters. We find that spiral galaxies within infalling groups have already begun a slow process of conversion into S0s, likely via gentle galaxy-galaxy interactions. The fates of spirals upon reaching the core of the cluster depend heavily on the cluster ICM, with rapid conversion of all remaining spirals into S0s via ram pressure stripping in clusters where the ICM is dense. In the presence of a less dense ICM, the conversion continues at a slower pace, with other mechanisms continuing to play a role. We conclude that the buildup of the local S0 population through the transformation of spiral galaxies is a heterogeneous process that nevertheless proceeds robustly across a variety of different environments.
|Additional Information:||© 2007 The American Astronomical Society. Received 2007 June 29; accepted 2007 July 26. We thank the referee, A. Boselli, for insightful comments, especially on the various physical processes and their timescales, which were helpful in revising the discussion of these issues. S. M. M. would like to thank T. Heckman, G. Kauffmann, S. Yi, and members of the GALEX science team for valuable discussions. Faint object spectroscopy at Keck Observatory is made possible with LRIS and DEIMOS thanks to the dedicated efforts of J. Cohen, P. Amico, S. Faber, and G. Wirth. We acknowledge use of the Gauss-Hermite Pixel Fitting Software developed by R. P. van der Marel. The analysis pipeline used to reduce the DEIMOS data was developed at UC Berkeley with support from NSF grant AST 00-71048. T. T. acknowledges support from the NSF through CAREER award NSF-0642621 and from the Sloan Foundation through a Sloan Research Fellowship. R. S. E. acknowledges financial support from NSF grant AST 03-07859 and STScI grants HST-GO-08559.01-A and HST-GO-09836.01-A. Finally, I. R. S. and G. P. S. acknowledge support from the Royal Society.|
|Subject Keywords:||galaxies : clusters : individual (Cl 0024+1654 MS 0451-0305); galaxies : elliptical and lenticular, cD; galaxies : evolution; galaxies : spiral; galaxies : stellar content; ultraviolet : galaxies|
|Official Citation:||A Wide-Field Survey of Two z ~ 0.5 Galaxy Clusters: Identifying the Physical Processes Responsible for the Observed Transformation of Spirals into S0s Sean M. Moran, Richard S. Ellis, Tommaso Treu, Graham P. Smith, R. Michael Rich, and Ian Smail 2007 ApJ 671 1503-1522 doi: 10.1086/522303|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||02 Mar 2010 17:29|
|Last Modified:||26 Dec 2012 11:47|
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