The distribution of mass and light in cluster infall regions
Abstract
The CAIRNS (Cluster And Infall Region Nearby Survey) project is a large spectroscopic survey of the infall regions surrounding nine nearby rich clusters of galaxies. I describe the survey and use the kinematics of galaxies in the infall regions to estimate the cluster mass profiles. At small radii, these mass profiles are consistent with independent mass estimates from X-ray observations and Jeans analysis. I demonstrate the dependence of mass-to-light ratios on environment by combining these mass profiles with Two-Micron All-Sky Survey (2MASS) photometry. Near-infrared light is more extended than mass in these clusters, suggesting that dense cluster cores are less efficient at forming galaxies and/or more efficient at disrupting them. At large radii, galaxy populations in cluster infall regions closely resemble those in the field. The mass-to-light ratio at these radii should therefore be a good probe of the global mass-to-light ratio. The mass-to-light ratio in the infall region yields a surprisingly low estimate of Ωm ∼ 0.1.
- Publication:
-
IAU Colloq. 195: Outskirts of Galaxy Clusters: Intense Life in the Suburbs
- Pub Date:
- July 2004
- DOI:
- 10.1017/S1743921304000419
- arXiv:
- arXiv:astro-ph/0404339
- Bibcode:
- 2004ogci.conf..193R
- Keywords:
-
- Astrophysics
- E-Print:
- 7 pages, 4 figures, to appear in the Proceedings of IAU Colloquium 195: "Outskirts of Galaxy Clusters: Intense Life in the Suburbs", Torino, Italy, March 2004, ed. A. Diaferio