1. Stellar and Total Baryon Mass Fractions in Groups and Clusters Since Redshift 1
- Author
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Alexie Leauthaud, Herve Aussel, Peter Capak, Simon J. Lilly, Alexis Finoguenov, Richard Massey, Hans Boehringer, Jason Rhodes, Shunji S. Sasaki, D. Pierini, Anton M. Koekemoer, Mara Salvato, H. J. McCracken, Yoshiaki Taniguchi, M. Bolzonella, Martin Elvis, David B. Sanders, N. Z. Scoville, Gabriel W. Pratt, S. Giodini, Vernesa Smolčić, Guenther Hasinger, D. Thompson, Luigi Guzzo, Olivier Ilbert, and Jeyhan S. Kartaltepe
- Subjects
Physics ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Stellar mass ,Diffuse radiation ,Cosmic microwave background ,Cosmological parameters ,Sigma ,galaxies: clusters. [X-rays] ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,clusters: general [Galaxies] ,Redshift ,Large sample ,Baryon ,Space and Planetary Science ,Galaxy group ,stellar content [Galaxies] ,observations [Cosmology] ,Mass fraction ,cosmological parameters ,cosmology: observations ,diffuse radiation ,galaxies: clusters: general ,galaxies: stellar content ,X-rays: galaxies: clusters ,Astrophysics::Galaxy Astrophysics ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
We investigate if the discrepancy between estimates of the total baryon mass fraction obtained from observations of the cosmic microwave background (CMB) and of galaxy groups/clusters persists when a large sample of groups is considered. To this purpose, 91 candidate X-ray groups/poor clusters at redshift 0.1 < z < 1 are selected from the COSMOS 2 deg^2 survey, based only on their X-ray luminosity and extent. This sample is complemented by 27 nearby clusters with a robust, analogous determination of the total and stellar mass inside R_500. The total sample of 118 groups and clusters with z < 1 spans a range in M_500 of ~10^13--10^15 M_sun. We find that the stellar mass fraction associated with galaxies at R_500 decreases with increasing total mass as (M_500)^-0.37 \pm 0.04, independent of redshift. Estimating the total gas mass fraction from a recently derived, high quality scaling relation, the total baryon mass fraction (f_500^stars+gas=f_500^stars+f_500^gas) is found to increase by ~ 25% when M_500 increases from =5 X 10^13 M_sun to = 7 X 10^14 M_sun. After consideration of a plausible contribution due to intra--cluster light (11--22% of the total stellar mass), and gas depletion through the hierarchical assembly process (10% of the gas mass), the estimated values of the total baryon mass fraction are still lower than the latest CMB measure of the same quantity (WMAP5), at a significance level of 3.3\sigma for groups of =5 X 10^13~M_sun. The discrepancy decreases towards higher total masses, such that it is 1\sigma at = 7 X 10^14~M_sun. We discuss this result in terms of non--gravitational processes such as feedback and filamentary heating., Comment: 14 pages, accepted for publication in ApJ. Revised discussion, added section on systematics
- Published
- 2009