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A statistical analysis of the galaxy populations of distant luminous X-ray clusters

Smail, Ian and Edge, Alastair C. and Ellis, Richard S. and Blandford, Roger D. (1998) A statistical analysis of the galaxy populations of distant luminous X-ray clusters. Monthly Notices of the Royal Astronomical Society, 293 (2). pp. 124-144. ISSN 0035-8711.

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We present a deep, multicolour (UBI) CCD survey using the Palomar 5‐m telescope of a sample of high X‐ray luminosity, distant clusters selected from the ROSAT All‐Sky Survey. The 10 clusters lie in the redshift range z= 0.22–0.28, an era in which evolutionary effects have been reported in the properties of cluster galaxy populations.Our clusters thus provide a well‐defined sample of the most massive systems at these redshifts with which to quantify the extent and variability of these evolutionary effects. The relatively low redshifts of these clusters also means that simple connections can be made between the galaxy populations of these clusters and their immediate descendents, local rich clusters. Moreover, by concentrating on a narrow redshift range, we can take advantage of the homogeneity of our cluster sample to combine the galaxy catalogues from all the clusters to analyse statistically the bulk properties of their populations. We present an analysis of the cluster galaxy populations using our multicolour data to probe the distribution, luminosities and star formation histories of galaxies in these regions. Our aim is to chart the characteristics of the galaxy populations of massive intermediate redshift clusters and to combine these into a wider scheme for galaxy evolution in high‐density environments. The core regions of clusters in our sample contain only a small proportion of star‐forming galaxies, and they therefore do not exhibit a classical “Butcher–Oemler” effect. Focusing on the redder cluster galaxies, we find that their integrated luminosity is well correlated with the X‐ray temperatures of the clusters, and hence with cluster mass. Furthermore, the typical rest frame UV–optical colours of the luminous elliptical sequences in the clusters exhibit a remarkably small cluster‐to‐cluster scatter, ≲2 per cent, indicating that these galaxies are highly homogeneous between cluster environments. However, at fainter magnitudes we observe a marked increase in the range of mid‐UV colours of galaxies possessing strong 4000‐Å breaks, as determined from photometry in ∼7.5 h^(‐1) kpc diameter apertures. In the light of the apparent decline in the population of S0 galaxies seen in distant z≳0.4, clusters, and in view of the luminosities and colours of this population, we propose that they may be the progenitors of the dominant S0 population of rich local clusters, caught in the final stage before they become completely quiescent. Further studies of this population will prove a necessary link with which to connect the evolution observed in cluster populations at high redshift with the nature of the final remnants locally. Observations in the rest frame UV will be important in these studies owing to the relative ease of detecting the signature of previous activity in this spectral region.

Item Type:Article
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URLURL TypeDescription Paper
Smail, Ian0000-0003-3037-257X
Ellis, Richard S.0000-0001-7782-7071
Blandford, Roger D.0000-0002-1854-5506
Additional Information:© 1998 RAS. Accepted 1997 August 27. Received 1997 August 27; in original form 1997 February 27. We would like to thank Steve Allen, Harald Ebeling, Andy Fabian and Hans Bohringer for their work in defining the X-ray sample on which our study is based. We also thank Jim McCarthy and Jim Westphal for their work in providing an efficient UV imaging capability on the 5-m, essential for our observations, as well as Jim Schombert for kindly loaning us his U filter, David Hogg for providing his deep U-field exposure, Alan Dressler for donating 5-m time to undertake the Bl imaging of the same field and David Buote for the analysis of the shapes of the cluster X-ray emission used in Fig. 11. We thank the referee, Phil James, for his thorough reading of the paper and constructive comments which improved the text, particularly in regard to the discussion of the models. Finally, we thank Rebecca Bernstein, Richard Bower, Julianne Dalcanton and Roger Davies for extensive discussions on the nature and evolution of cluster galaxies. IRS acknowledges support from a PPARC Advanced Fellowship and ACE from a Royal Society Fellowship. RDB acknowledges NSF grants AST 92-23370 and AST 95-29170. The research published here used the STARLINK computer resources at the University of Durham. This work is based on observations obtained at Palomar Observatory, which is owned and operated by the California Institute of Technology.
Funding AgencyGrant Number
Particle Physics and Astronomy Research Council (PPARC)UNSPECIFIED
NSFAST 92-23370
NSFAST 95-29170
Subject Keywords:galaxies: clusters: general - galaxies: luminosity function, mass function - galaxies: photometry - cosmology: observations - X-rays: general.
Issue or Number:2
Record Number:CaltechAUTHORS:20190531-150238466
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Official Citation:Smail, I. , Edge, A. C., Ellis, R. S. and Blandford, R. D. (1998), A statistical analysis of the galaxy populations of distant luminous X‐ray clusters. Monthly Notices of the Royal Astronomical Society, 293: 124-144. doi:10.1046/j.1365-8711.1998.2932124.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96017
Deposited By: Tony Diaz
Deposited On:31 May 2019 22:10
Last Modified:03 Oct 2019 21:18

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