TY - JOUR
T1 - The colour-magnitude relations of ClJ1226.9+3332, a massive cluster of galaxies at z = 0.89
AU - Ellis, S. C.
AU - Jones, L. R.
AU - Donovan, D.
AU - Ebeling, H.
AU - Khosroshahi, H. G.
PY - 2006/5/1
Y1 - 2006/5/1
N2 - 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 z f ≳ 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.
AB - 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 z f ≳ 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.
KW - Galaxies: clusters: individual: ClJ1226.9+3332
KW - Galaxies: evolution
UR - http://www.scopus.com/inward/record.url?scp=33646262576&partnerID=8YFLogxK
U2 - 10.1111/j.1365-2966.2006.10143.x
DO - 10.1111/j.1365-2966.2006.10143.x
M3 - Article
AN - SCOPUS:33646262576
SN - 0035-8711
VL - 368
SP - 769
EP - 780
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -