The Environmental Dependence of the Evolving S0 Fraction
Abstract
We re-investigate the dramatic rise in the S0 fraction, f S0, within clusters since z ~ 0.5. In particular, we focus on the role of the global galaxy environment on f S0 by compiling, either from our own observations or the literature, robust line-of-sight velocity dispersions, σ's, for a sample of galaxy groups and clusters at 0.1 < z < 0.8 that have uniformly determined, published morphological fractions. We find that the trend of f S0 with redshift is twice as strong for σ < 750 km s-1 groups/poor clusters than for higher-σ, rich clusters. From this result, we infer that over this redshift range galaxy-galaxy interactions, which are more effective in lower-σ environments, are more responsible for transforming spiral galaxies into S0's than galaxy-environment processes, which are more effective in higher-σ environments. The rapid, recent growth of the S0 population in groups and poor clusters implies that large numbers of progenitors exist in low-σ systems at modest redshifts (~0.5), where morphologies and internal kinematics are within the measurement range of current technology.
Observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution; and based on data collected at the Magellan Telescope, which is operated by the Carnegie Observatories.- Publication:
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The Astrophysical Journal
- Pub Date:
- March 2010
- DOI:
- 10.1088/0004-637X/711/1/192
- arXiv:
- arXiv:1001.2008
- Bibcode:
- 2010ApJ...711..192J
- Keywords:
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- galaxies: clusters: general;
- galaxies: evolution;
- galaxies: groups: general;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- Accepted for publication in The Astrophysical Journal. 13 pages, 6 figures