Details

Autor(en) / Beteiligte

• Giodini, S
• Pierini, D
• Finoguenov, A
• Pratt, G. W
• Boehringer, H
• Leauthaud, A
• Guzzo, L
• Aussel, H
• Bolzonella, M
• Capak, P
• Elvis, M
• Hasinger, G
• Ilbert, O
• Kartaltepe, J. S
• Koekemoer, A. M
• Lilly, S. J
• Massey, R
• McCracken, H. J
• Rhodes, J
• Salvato, M
• Sanders, D. B
• Scoville, N. Z
• Sasaki, S
• Smolcic, V
• Taniguchi, Y
• Thompson, D
• the COSMOS Collaboration

Titel

Stellar and Total Baryon Mass Fractions in Groups and Clusters Since Redshift 1

Ist Teil von

• The Astrophysical journal, 2009-09, Vol.703 (1), p.982-993

Ort / Verlag

Bristol: IOP Publishing

Erscheinungsjahr

2009

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• 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 ☉ . We find that the stellar mass fraction associated with galaxies at R 500 decreases with increasing total mass as M −0.37 ± 0.04 500 , independent of redshift. Estimating the total gas mass fraction from a recently derived, high-quality scaling relation, the total baryon mass fraction ( f stars+gas 500 = f stars 500 + f gas 500 ) is found to increase by ∼25%, when M 500 increases from 〈 M 〉 = 5 × 10 13 M ☉ to 〈 M 〉 = 7 × 10 14 M ☉ . After consideration of a plausible contribution due to intracluster 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 3.3σ for groups of 〈 M 〉 = 5 × 10 13 M ☉ . The discrepancy decreases toward higher total masses, such that it is 1σ at 〈 M 〉 = 7 × 10 14 M ☉ . We discuss this result in terms of nongravitational processes such as feedback and filamentary heating.