N. Gupta

THE EVOLUTION OF THE INTRACLUSTER MEDIUM METALLICITY IN SUNYAEV ZEL’DOVICH-SELECTED GALAXY CLUSTERS AT 0 < z < 1.5

We present the results of an X-ray spectral analysis of 153 galaxy clusters observed with the Chandra, XMM-Newton, and Suzaku space telescopes. These clusters, which span 0 = 0.23 +/- 0.01 Zsun and a scatter of 0.08 +/- 0.01 Zsun. These results imply that >60% of the metals in the ICM were already in place at z=1 (at 95% confidence), consistent with the picture of an early (z>1) enrichment. We find, in agreement with previous works, a significantly higher mean value for the metallicity in the centers of cool core clusters versus non-cool core clusters. We find weak evidence for evolution in the central metallicity of cool core clusters (dZ/dz = -0.21 +/- 0.11 Zsun), which is sufficient to account for this enhanced central metallicity over the past ~10 Gyr. We find no evidence for metallicity evolution outside of the core (dZ/dz = -0.03 +/- 0.06 Zsun), and no significant difference in the core-excised metallicity between cool core and non-cool core clusters. This suggests that strong radio-mode AGN feedback does not significantly alter the distribution of metals at r>0.15R500. Given the limitations of current-generation X-ray telescopes in constraining the ICM metallicity at z>1, significant improvements on this work will likely require next-generation X-ray missions.

Galaxy populations in massive galaxy clusters to z = 1.1: color distribution, concentration, halo occupation number and red sequence fraction

We study the galaxy populations in 74 Sunyaev Zeldovich Effect (SZE) selected clusters from the South Pole Telescope (SPT) survey that have been imaged in the science verification phase of the Dark Energy Survey (DES). The sample extends up to z ˜ 1.1 with 4 × 1014Ms <= M200 <= 3 × 1015Ms. Using the band containing the 4000 A break and its redward neighbor, we study the color-magnitude distributions of cluster galaxies to ˜m* + 2, finding: (1) the intrinsic rest frame g - r color width of the red sequence (RS) population is ˜0.03 out to z ˜ 0.85 with a preference for an increase to ˜0.07 at z = 1 and (2) the prominence of the RS declines beyond z ˜ 0.6. The spatial distribution of cluster galaxies is well described by the NFW profile out to 4R200 with a concentration of cg = 3.59^{+0.20}_{-0.18}, 5.37^{+0.27}_{-0.24} and 1.38^{+0.21}_{-0.19} for the full, the RS and the blue non-RS populations, respectively, but with ˜40% to 55% cluster to cluster variation and no statistically significant redshift or mass trends. The number of galaxies within the virial region N200 exhibits a mass trend indicating that the number of galaxies per unit total mass is lower in the most massive clusters, and shows no significant redshift trend. The red sequence (RS) fraction within R200 is (68 ± 3)% at z = 0.46, varies from ˜55% at z = 1 to ˜80% at z = 0.1, and exhibits intrinsic variation among clusters of ˜14%. We discuss a model that suggests the observed redshift trend in RS fraction favors a transformation timescale for infalling field galaxies to become RS galaxies of 2 to 3 Gyr.

SPT-GMOS: A Gemini/GMOS-South Spectroscopic Survey of Galaxy Clusters in the SPT-SZ Survey

National Science Foundation [AST-1009012, PHY-1125897]; Kavli Foundation; Gordon and Betty Moore Foundation [GBMF 947]; NSF [AST-1009649, MRI-0723073]; Alfred P. Sloan Foundation; U.S. Department of Energy [DE-AC02-06CH11357]; Fermi Research Alliance, LLC [DE-AC02-07CH11359]; United States Department of Energy; NASA through Space Telescope Science Institute [HST-GO-13412.004-A]; NASA [NAS 5-26555]; [GS-2011A-C-03]; [GS-2011A-C-04]; [GS-2011B-C-06]; [GS-2011B-C-33]; [GS-2012A-Q-04]; [GS-2012A-Q-37]; [GS-2012B-Q-29]; [GS-2012B-Q-59]; [GS-2013A-Q-05]; [GS-2013A-Q-45]; [GS-2013B-Q-25]; [GS-2013B-Q-72]; [GS-2014B-Q-31]; [GS-2014B-Q-64]; [13412]