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Infall, the Butcher-Oemler Effect, and the Descendants of Blue Cluster Galaxies at z~0.6

Kim-Vy H. Tran·Pieter van Dokkum·Garth D. Illingworth·Daniel Kelson·Anthony Gonzalez·Marijn Franx
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Abstract

Using wide-field HST/WFPC2 imaging and extensive Keck/LRIS spectroscopy, we present a detailed study of the galaxy populations in MS2053--04, a massive, X-ray luminous cluster at z=0.5866. Analysis of 149 confirmed cluster members shows that MS2053 is composed of two structures that are gravitationally bound to each other; their respective velocity dispersions are 865 km/s (113 members) and 282 km/s (36 members). MS2053's total dynamical mass is 1.2x10^15 Msun. MS2053 is a classic Butcher-Oemler cluster with a high fraction of blue members (24%) and an even higher fraction of star-forming members (44%), as determined from their [OII] emission. The number fraction of blue/star-forming galaxies is much higher in the infalling structure than in the main cluster. This result is the most direct evidence to date that the Butcher-Oemler effect is linked to galaxy infall. In terms of their colors, luminosities, estimated internal velocity dispersions, and [OII] equivalent widths, the infalling galaxies are indistinguishable from the field population. MS2053's deficit of S0 galaxies combined with its overabundance of blue spirals implies that many of these late-types will evolve into S0 members. The properties of the blue cluster members in both the main cluster and infalling structure indicate they will evolve into low mass, L 3.

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Kim-Vy H. Tran, Pieter van Dokkum, Garth D. Illingworth, Daniel Kelson, Anthony Gonzalez, Marijn Franx. 2004-09-28. Infall, the Butcher-Oemler Effect, and the Descendants of Blue Cluster Galaxies at z~0.6. https://doi.org/10.1086/426427

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