• The MACS team
• Project overview
• The sample
• Publications

The MACS team:

• Harald Ebeling, University of Hawaii, USA
• Alastair Edge, University of Durham, UK
• J. Patrick Henry, University of Hawaii, USA

• Nick Kaiser, University of Hawaii, USA
• Leon Van Speybroeck, SAO/CfA, Cambridge, MA, USA
• John Carlstrom, University of Chicago, USA
• Marshall Joy, MSFC, Huntsville, USA

Project overview:

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

To achieve these goals we apply 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.

At present the MACS cluster sample comprises 101 spectroscopically confirmed clusters at 0.3 < z < 0.6; more than two thirds of these are new discoveries. Our preliminary sample is already 15 times larger than that of the EMSS in the same redshift and X-ray luminosity range.

Comprehensive follow-up observations of MACS clusters are being performed as the survey proceeds. 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, and measurements of the cluster gas and temperature distribution via deep pointed X-ray observations with the ACIS instrument aboard the Chandra X-ray Observatory.

The sample:

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

Weather permitting we shall finish the compilation of a statistically complete subset of the X-ray brightest MACS clusters by mid 2001. We intend to publish the resulting subsample before the end of the year.

MACS publications (by the MACS team):

• Ebeling H., Edge A.C., Henry J.P.

  MACS: A quest for the most massive galaxy clusters in the universe, 2001, ApJ, 553, 668 (see also preprint)

(page last updated by H. Ebeling, June 13, 2001)