TY - JOUR

T1 - The XMM cluster survey

T2 - Galaxy morphologies and the color-magnitude relation in XMMXCS J2215.9 - 1738 at z = 1.46

AU - Hilton, Matt

AU - Stanford, S. Adam

AU - Stott, John P.

AU - Collins, Chris A.

AU - Hoyle, Ben

AU - Davidson, Michael

AU - Hosmer, Mark

AU - Kay, Scott T.

AU - Liddle, Andrew R.

AU - Lloyd-Davies, Ed

AU - Mann, Robert G.

AU - Mehrtens, Nicola

AU - Miller, Christopher J.

AU - Nichol, Robert C.

AU - Romer, A. Kathy

AU - Sabirli, Kivanc

AU - Sahlén, Martin

AU - Viana, Pedro T P

AU - West, Michael J.

AU - Barbary, Kyle

AU - Dawson, Kyle S.

AU - Meyers, Joshua

AU - Perlmutter, Saul

AU - Rubin, David

AU - Suzuki, Nao

PY - 2009/5/1

Y1 - 2009/5/1

N2 - We present a study of the morphological fractions and color-magnitude relation (CMR) in the most distant X-ray selected galaxy cluster currently known, XMMXCS J2215.9 - 1738 at z = 1.46, using a combination of optical imaging data obtained with the Hubble Space Telescope Advanced Camera for Surveys, and infrared data from the Multi-Object Infrared Camera and Spectrograph, mounted on the 8.2 m Subaru telescope. We find that the morphological mix of the cluster galaxy population is similar to clusters at z 1. Within the central 0.5 Mpc, approximately 62% of the galaxies identified as likely cluster members are ellipticals or S0s; and 38% are spirals or irregulars. Therefore, early-type galaxies were already entrenched as the dominant galaxy population in at least some clusters approximately 4.5 Gyr after the big bang. We measure the CMRs for the early-type galaxies, finding that the slope in the z 850-J relation is consistent with that measured in the Coma cluster, some 9 Gyr earlier, although the uncertainty is large. In contrast, the measured intrinsic scatter about the CMR is more than three times the value measured in Coma, after conversion to rest-frame U - V. From comparison with stellar population synthesis models, the intrinsic scatter measurements imply mean luminosity-weighted ages for the early-type galaxies in J2215.9 - 1738 of 3 Gyr, corresponding to the major epoch of star formation coming to an end at z f 3-5. We find that the cluster exhibits evidence of the "downsizing" phenomenon: the fraction of faint cluster members on the red sequence expressed using the Dwarf-to-Giant Ratio (DGR) is 0.32 0.18 within a radius of 0.5R 200. This is consistent with extrapolation of the redshift evolution of the DGR seen in cluster samples at z <1. In contrast to observations of some other z > 1 clusters, we find a lack of very bright galaxies within the cluster.

AB - We present a study of the morphological fractions and color-magnitude relation (CMR) in the most distant X-ray selected galaxy cluster currently known, XMMXCS J2215.9 - 1738 at z = 1.46, using a combination of optical imaging data obtained with the Hubble Space Telescope Advanced Camera for Surveys, and infrared data from the Multi-Object Infrared Camera and Spectrograph, mounted on the 8.2 m Subaru telescope. We find that the morphological mix of the cluster galaxy population is similar to clusters at z 1. Within the central 0.5 Mpc, approximately 62% of the galaxies identified as likely cluster members are ellipticals or S0s; and 38% are spirals or irregulars. Therefore, early-type galaxies were already entrenched as the dominant galaxy population in at least some clusters approximately 4.5 Gyr after the big bang. We measure the CMRs for the early-type galaxies, finding that the slope in the z 850-J relation is consistent with that measured in the Coma cluster, some 9 Gyr earlier, although the uncertainty is large. In contrast, the measured intrinsic scatter about the CMR is more than three times the value measured in Coma, after conversion to rest-frame U - V. From comparison with stellar population synthesis models, the intrinsic scatter measurements imply mean luminosity-weighted ages for the early-type galaxies in J2215.9 - 1738 of 3 Gyr, corresponding to the major epoch of star formation coming to an end at z f 3-5. We find that the cluster exhibits evidence of the "downsizing" phenomenon: the fraction of faint cluster members on the red sequence expressed using the Dwarf-to-Giant Ratio (DGR) is 0.32 0.18 within a radius of 0.5R 200. This is consistent with extrapolation of the redshift evolution of the DGR seen in cluster samples at z <1. In contrast to observations of some other z > 1 clusters, we find a lack of very bright galaxies within the cluster.

KW - Galaxies: clusters: individual (XMMXCS J2215.9-1738)

KW - Galaxies: elliptical and lenticular, cD

KW - Galaxies: evolution

KW - X-rays: galaxies: clusters

U2 - 10.1088/0004-637X/697/1/436

DO - 10.1088/0004-637X/697/1/436

M3 - Journal article

AN - SCOPUS:66649099961

VL - 697

SP - 436

EP - 451

JO - The Astrophysical Journal

JF - The Astrophysical Journal

SN - 0004-637X

IS - 1

ER -