AAS 205th Meeting, 9-13 January 2005
Session 161 Cluster Evolution and Large Scale Structure
Oral, Thursday, January 13, 2005, 10:00-11:30am, Sunrise

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[161.03] Velocity Dispersions of Six Galaxy Clusters at 0.83

T. Goto (JHU), HST/ACS Team

There have been plenty of observational evidence of cluster galaxy evolution such as the Butcher-Oemler effect and the morphology-density relation. However, it has been difficult to identify the responsible physical mechanism for the cluster galaxy evolution. It has been simply difficult to trace the complicated process of galaxy evolution with several giga years of timescale, using the observation which only brings us with information of a single epoch. One of the actively debated candidate mechanisms is the ram-pressure stripping model, where the cold (or hot) galaxy gas is stripped away by the intra-cluster gas, quenching the star-formation in the galaxy. In this letter, we test if the ram-pressure stripping is mainly responsible for the cluster galaxy evolution by investigating velocity dispersion for various sub-samples of cluster galaxies selected using both morphology and color. It is critical to have both morphological and color information since the results based on one of them has been difficult to be interpreted previously.

To this purpose, we have obtained the accurate morphological information from the HST/ACS and the large number of spectroscopic cluster member redshifts for 6 galaxy clusters at 0.832 (i.e., stronger for galaxies with high velocity), the ram-pressure stripping models cannot explain the observed trends of red (evolved) galaxies having low velocity rather than high velocity. On the other hand, the dynamical galaxy-galaxy interaction models are more consistent with the observed results since the galaxy-galaxy interaction occurs more frequently for galaxies with low velocity.

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The author(s) of this abstract have provided an email address for comments about the abstract: tomo@jhu.edu

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© 2004. The American Astronomical Society.