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OATS-DAUT SEMINAR
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Speaker: Joseph Mohr (Ludwig Maximilians University, Munich, Germany)
Title: The Cluster Baryon Budget and Cosmology with the SPT Galaxy Cluster Sample
Date: Friday, March 21st, 2014
Time: 11:30
Venue: Villa Bazzoni
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Abstract The SPT-SZ galaxy cluster sample contains 508 clusters with measured redshifts and detection significance >4.5 over the 2500 deg2 survey region. The highest redshift, spectroscopically confirmed SPT cluster so far is at z=1.5. Mass calibration using velocity dispersions, weak lensing and X-ray observables is underway. The latest cosmological results including the velocity dispersion mass information indicate good agreement with CMB anisotropy constraints (at ~1.5sigma level); improved mass estimates indicate that these clusters have masses M_200 > 3x10^14 Mo with characteristic single cluster mass uncertainties of 25%. We study the galaxy populations and baryon budget in two cluster subsamples. The first is a complete sample of 75 clusters lying within ~200 deg2 of Dark Energy Survey imaging, and the second is a subsample of 14 clusters with median redshift z=0.9 with deep VLT and HST
imaging as well as Chandra and XMM observations. We explore the redshift
evolution and mass sensitivity of the galaxy halo occupation distribution, the stellar mass fraction and the cold baryonic fraction. Results indicate an accumulation of fainter galaxies in the cluster galaxy population over cosmic time, and are consistent with (1) falling stellar mass fraction and cold fraction with mass and (2) no redshift evolution of the stellar mass fraction or cold fraction. These results raise interesting questions about how massive clusters can be built up over time out of lower mass building blocks that exhibit different stellar and cold fractions.
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Contact: Marisa Girardi (UNITS)