Abstract
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.
| Language | English |
|---|---|
| Pages | 769-780 |
| Number of pages | 12 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 368 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - 1 May 2006 |
| Externally published | Yes |
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Keywords
- Galaxies: clusters: individual: ClJ1226.9+3332
- Galaxies: evolution
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The colour-magnitude relations of ClJ1226.9+3332, a massive cluster of galaxies at z = 0.89. / Ellis, S. C.; Jones, L. R.; Donovan, D.; Ebeling, H.; Khosroshahi, H. G.
In: Monthly Notices of the Royal Astronomical Society, Vol. 368, No. 2, 01.05.2006, p. 769-780.Research output: Contribution to journal › Article › Research › peer-review
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
VL - 368
SP - 769
EP - 780
JO - Monthly Notices of the Royal Astronomical Society
T2 - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 2
ER -