Exploring the selection of galaxy clusters and groups: an optical survey for X-ray dark clusters

Data from a new, wide-field, coincident optical and X-ray survey, the X-ray Dark Cluster Survey (XDCS), are presented. This survey comprises simultaneous and independent searches for clusters of galaxies in the optical and X-ray passbands. Optical cluster detection algorithms implemented on the data...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2004-02, Vol.348 (2), p.551-580
Main Authors: Gilbank, David G., Bower, Richard G., Castander, F. J., Ziegler, B. L.
Format: Article
Language:English
Subjects:
Astronomy
cosmology: miscellaneous
Earth, ocean, space
Exact sciences and technology
galaxies: clusters: general
Galaxy clusters
Galaxy groups, clusters, and superclusters. Large-scale structure of the universe
Stellar systems. Galactic and extragalactic objects and systems. The universe
surveys
X-rays: galaxies: clusters
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Summary:Data from a new, wide-field, coincident optical and X-ray survey, the X-ray Dark Cluster Survey (XDCS), are presented. This survey comprises simultaneous and independent searches for clusters of galaxies in the optical and X-ray passbands. Optical cluster detection algorithms implemented on the data are detailed. Two distinct optically selected catalogues are constructed, one based on I-band overdensity, the other on overdensities of colour-selected galaxies. The superior accuracy of the colour-selection technique over that of the single-passband method is demonstrated, via internal consistency checks and comparison with external spectroscopic redshift information. This is compared with an X-ray-selected cluster catalogue. In terms of gross numbers, the survey yields 185 I-band-selected, 290 colour-selected and 15 X-ray-selected systems, residing in ∼11 deg2 of optical + X-ray imaging. The relationship between optical richness/luminosity and X-ray luminosity is examined, by measuring X-ray luminosities at the positions of our 290 colour-selected systems. Power-law correlations between the optical richness/luminosity and X-ray luminosity are fitted, both exhibiting approximately 0.2 dex of intrinsic scatter. Interesting outliers in these correlations are discussed in greater detail. Spectroscopic follow-up of a subsample of X-ray underluminous systems confirms their reality.
ISSN:0035-8711
1365-2966
DOI:10.1111/j.1365-2966.2004.07335.x