The Northern ROSAT All-Sky (NORAS) Galaxy Cluster Survey. I. X-Ray Properties of Clusters Detected as Extended X-Ray Sources

By H. Böhringer, W. Voges, J. Huchra, B. McLean, R. Giacconi, Piero Rosati, R. Burg, J. Mader, P. Schuecker, D. Simic and 4 more. 2000

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In the construction of an X-ray-selected sample of galaxy clusters for cosmological studies, we have assembled a sample of 495 X-ray sources found to show extended X-ray emission in the first processing of the ROSAT All-Sky Survey. The sample covers the celestial region with declination δ ≥ 0° and Galactic latitude |bII| ≥ 20° and comprises sources with a count rate ≥0.06 counts s-1 and a source extent likelihood of L ≥ 7. In an optical follow-up identification program we find 378 (76%) of these sources to be clusters of galaxies. It was necessary to reanalyze the sources in this sample with a new X-ray source characterization technique to provide more precise values for the X-ray flux and source extent than obtained from the standard processing. This new method, termed growth curve analysis (GCA), has the advantage over previous methods in its ability to be robust, to be easy to model and to integrate into simulations, to provide diagnostic plots for visual inspection, and to make extensive use of the X-ray data. The source parameters obtained assist the source identification and provide more precise X-ray fluxes. This reanalysis is based on data from the more recent second processing of the ROSAT Survey. We present a catalog of the cluster sources with the X-ray properties obtained as well as a list of the previously flagged extended sources that are found to have a noncluster counterpart. We discuss the process of source identification from the combination of optical and X-ray data. To investigate the overall completeness of the cluster sample as a function of the X-ray flux limit, we extend the search for X-ray cluster sources to the data of the second processing of the ROSAT Survey for the northern sky region between 9h and 14h in right ascension. We include the search for X-ray emission of known clusters as well as a new investigation of extended X-ray sources. In the course of this search we find X-ray emission from 85 additional Abell clusters and 56 very probable cluster candidates among the newly found extended sources. A comparison of the X-ray cluster number counts of the NORAS sample with the ROSAT-ESO Flux-limited X-Ray (REFLEX) Cluster Survey results leads to an estimate of the completeness of the NORAS sample of ROSAT All-Sky Survey (RASS) I extended clusters of about 50% at an X-ray flux of FX(0.1-2.4 keV) = 3 × 10-12 ergs s-1 cm-2. The estimated completeness achieved by adding the supplementary sample in the study area amounts to about 82% in comparison to REFLEX. The low completeness introduces an uncertainty in the use of the sample for cosmological statistical studies that will be cured with the completion of the continuing Northern ROSAT All-Sky (NORAS) Cluster Survey project.

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Citations in the corpus

Probing cosmic isotropy with a new X-ray galaxy cluster sample through the LX–T scaling relation (2020, unknown): “The parent catalogs of the clusters we use are The ROSAT extended Brightest Cluster Sample (eBCS, Ebeling et al. 2000), The Northern ROSAT All-Sky (NORAS) Galaxy Cluster Survey (Böhringer et al. 2000) and the ROSAT-ESO Flux-Limited X-Ray (REFLEX) Galaxy Cluster Survey Catalog (Böhringer et al. 2004)”
Planck 2013 results. XX. Cosmology from Sunyaev-Zeldovich cluster counts (2013, unknown): “X-ray cluster surveys include both the NORAS (Böhringer et al. 2000) and REFLEX (Böhringer et al. 2004) surveys, based on ROSAT satellite observations, which have been used as source catalogues for higher-precision observations by the Chandra and XMM-Newton satellites, as well as surveys with…”
The Red-Sequence Cluster Survey. I. The Survey and Cluster Catalogs for Patches RCS 0926+37 and RCS 1327+29 (2004, unknown): “…Gioia et al. 1990; Dalton et al. 1992; Lumsden et al. 1992; Scharf et al. 1997; Ebeling et al. 1998; Rosati et al. 1998; Vikhlinin et al. 1998; Böhringer et al. 2000; Bramel et al. 2000; Gal et al. 2000; Romer et al. 2000; Ebeling et al. 2001; Bahcall et al. 2003a; Gilbank et al. 2003;…”
A GMBCG GALAXY CLUSTER CATALOG OF 55,424 RICH CLUSTERS FROM SDSS DR7 (2010, unknown): “NORAS and REFLEX consist of clusters identified from extended sources on the ROSAT all-sky survey X-ray maps.”
Scaling Properties of a Complete X-ray Selected Galaxy Group Sample (2014, unknown): “We constructed a complete sample of galaxy groups by applying a flux limit and two redshift cuts to the NORAS and REFLEX catalogs (Böhringer et al. 2000, 2004, respectively).”
K-Band Properties of Galaxy Clusters and Groups: Luminosity Function, Radial Distribution, and Halo Occupation Number (2004, unknown): “The X-ray centers are either estimated from archival ROSAT images or taken from the literature (Reiprich & Böhringer 2002; Böhringer et al. 2000; Ebeling et al. 1996, 1998).”
A CATALOG OF 132,684 CLUSTERS OF GALAXIES IDENTIFIED FROM SLOAN DIGITAL SKY SURVEY III (2012, unknown): “We get X-ray clusters from the Northern ROSAT All-Sky (NORAS) Galaxy Cluster Survey (Böhringer et al. 2000) and the ROSAT-ESO Flux Limited X-ray (REFLEX) Galaxy cluster survey (Böhringer et al. 2004).”
A WEAK LENSING STUDY OF X-RAY GROUPS IN THE COSMOS SURVEY: FORM AND EVOLUTION OF THE MASS–LUMINOSITY RELATION (2009, unknown): “…(e.g. Sunyaev & Zeldovich 1970, 1972; Carlstrom et al. 2002; Benson et al. 2004; Staniszewski et al. 2008), c) detection via X-ray emission (e.g. Böhringer et al. 2000; Hasinger et al. 2001; Finoguenov et al. 2007; Vikhlinin et al. 2008), d) spectroscopic identification (e.g. Gerke et al.…”
The MCXC: a meta-catalogue of x-ray detected clusters of galaxies (2010, unknown): “R. Piffaretti et al.: The MCXC For both catalogues data (Böhringer et al. 2000b, 2004b) are retrieved from VizieR2.”
Searching for cool core clusters at high redshift (2008, unknown): “The cluster number counts were determined using the growth curve analysis (Böhringer et al. 2000): cluster counts are calculated in circular apertures until the background level is reached.”
A Systematic X-Ray Search for Clusters of Galaxies behind the Milky Way (2002, unknown): “The NorthernROSATAll-Sky (NORAS) cluster list (Böhringer et al. 2000), also compiled from RASS data, covers the same area but is of limited use for LSS studies because of its low completeness of only d50%.”
A MaxBCG Catalog of 13,823 Galaxy Clusters from the Sloan Digital Sky Survey (2007, unknown): “It is important to note that the NORAS catalog was based on early selection of extended sources and as a result is not as complete or pure as the later REFLEX catalog.”
MEASURING THE ULTIMATE HALO MASS OF GALAXY CLUSTERS: REDSHIFTS AND MASS PROFILES FROM THE HECTOSPEC CLUSTER SURVEY (HeCS) (2012, unknown): “BCS splits A1758 into two components, neither of which alone would lie above our flux limit; however, the NORAS catalog (Böhringer et al. 2000) merges these components, yielding a flux above our flux limit.”
The 400 Square Degree ROSAT PSPC Galaxy Cluster Survey: Catalog and Statistical Calibration (2006, unknown): “— Cluster redshift references are: 1 — Vikhlinin et al. (1998a); Mullis et al. (2003); 2 — Cappi et al. (1998); 3 — Struble & Rood (1999); 4 — Mahdavi & Geller (2004); 5 — Rines et al. (2003); 6 — Simien & Prugniel (2000); 7 — Huchra et al. (1999); 8 — Perlman et al. (2002); 9 — Romer et al. (2000);”
CIRS: Cluster Infall Regions in the Sloan Digital Sky Survey. I. Infall Patterns and Mass Profiles (2006, unknown): “REFLEX (Böhringer et al. 2001, 2004) is analogous to NORAS but for the southern hemisphere.”