The most X-ray luminous distant clusters of galaxies from ROSAT All-Sky Survey data:

MACS logo
The MAssive Cluster Survey

The MACS team:

MACS follow-up projects are being conducted in collaboration with:
  • Nick Kaiser, University of Hawaii, USA
  • Leon Van Speybroeck, SAO/CfA, Cambridge, MA, USA
  • Alastair Edge, University of Durham, UK
  • Jean-Paul Kneib, OMP, Marseille, France
  • Johan Richard, University of Durham, UK
  • Cheng-Jiun Ma, CfA, Cambridge, MA, USA
  • Marceau Limousin, OMP, Marseille, France
  • Adam Mantz, GSFC, USA
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Project overview:

The MAssive Cluster Survey (MACS) is an ongoing project aimed at the compilation and characterization of a statistically complete sample of very X-ray luminous (and thus, by inference, massive), distant clusters of galaxies. The primary goal of MACS was to increase the number of known massive clusters at z > 0.3 from a handful to a hundred. The final MACS cluster sample has greatly improved our ability to study quantitatively the physical and cosmological parameters driving cluster evolution at redshifts and luminosities poorly sampled by all previous cluster surveys.

To achieve these goals we applied an X-ray flux and X-ray hardness-ratio cut to select distant cluster candidates from the ROSAT Bright Source Catalogue. Starting from a list of more than 5,000 X-ray sources within the survey area of 22,735 square degrees we use positional cross-correlations with public catalogues of Galactic and extragalactic objects, reference to APM colours, visual inspection of Digitized Sky Survey images, extensive CCD imaging, and finally spectroscopic observations with the University of Hawaii's 2.2m and the Keck 10m telescopes to compile the final cluster sample.

The MACS cluster sample comprises 124 spectroscopically confirmed clusters at 0.3 < z < 0.7; more than two thirds of these are new discoveries. This sample is over 20 times larger than that of the EMSS in the same redshift and X-ray luminosity range.

Comprehensive follow-up observations of MACS clusters were launched as the survey proceeded. These follow-up efforts include: V,R,I band imaging with the University of Hawaii's 2.2m telescope, weak-lensing mass measurements using wide-field imaging data obtained with the prime focus camera of the Subaru 8m telescope, virial mass estimates based on cluster galaxy velocity dispersions measured with the CFHT 3.6m and Keck-I 10m telescopes, SZ observations with the BIMA mm-wave radio interferometer, measurements of the cluster gas and temperature distribution via deep pointed X-ray observations with the ACIS instrument aboard the Chandra X-ray Observatory, and both deep, multi-passband and snapshot images with the Hubble Space Telescope.

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The sample:

The Lx-z distribution of MACS clusters is shown in the following figure.

The compilation of statistically complete subsets of the MACS sample was pursued both as a function of redshift and of X-ray flux. The sample of the 12 most distant MACS clusters (z>0.5) was published in 2007, and the 34 X-ray brightest ones were the subject of a 2010 paper. We continue to conduct follow-up studies on many individually exciting systems (such as MACSJ0717.5+3745).

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Selected MACS publications:

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(page last updated August, 2010 by H. Ebeling)