2006/02/06 by S. C. Ellis, Simon Ellis, L. R. Jones +4 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2006.10143.x
published as Mon.Not.Roy.Astron.Soc.368:769-780,2006 · Accepted for publication in MNRAS. 14 pages, 5 figures
arxiv created 2006/02/06 · openalex publication_date 2006/03/27 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
The colour–magnitude relations (CMRs) of one of the most massive (≈1015 M⊙), high-redshift (z= 0.89) clusters of galaxies known have been studied. Photometry has been measured in the V, R, I, z, F606W, F814W, J and K bands to a depth of K≈ 20.5 =K*+ 2.5 and spectroscopy confirms 27 K-band selected galaxies as members of the cluster. The V−K colours are equivalent to a rest-frame colour of ≈2700 Å−J, and provide a very sensitive measure of star formation activity. The Hubble Space Telescope imaging with the Advanced Camera for Surveys has been used to morphologically classify the galaxies. The cluster has a low early-type fraction compared to nearby clusters, with only 33 per cent of the confirmed cluster members having types E or S0. The early-type member galaxies form a clear red-sequence in all colours. The scatter and slope of the relations show no evolution compared to the equivalent Coma cluster relations, suggesting the stellar populations are already very old at z= 0.89. The normalization of the relations has been compared to models based on synthetic stellar populations (SSPs), and are most consistent with stellar populations forming at zf≳ 3. Some galaxies of late-type morphology were found to lie on the red-sequence of the CMR, suggesting that they have very similar stellar populations to the early-type galaxies. These results present a picture of a cluster in which the early-type galaxies are all old, but in which there must be future morphological transformation of galaxies to match the early-type fraction of nearby clusters. In order to preserve the tight CMR of early types seen in nearby clusters, the late-type galaxies must transform their colours, through the cessation of star formation, before the morphological transformation occurs. Such evolution is observed in the late types lying on the CMR.