Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26a...278..379b&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 278, no. 2, p. 379-390
Astronomy and Astrophysics
Astronomy
53
Big Bang Cosmology, Dark Matter, Galactic Clusters, X Ray Astronomy, X Ray Sources, X Rays, Atmospheric Density, Red Shift, Rosat Mission, Sky Surveys (Astronomy), Stellar Luminosity, X Ray Telescopes
Scientific paper
The ROSAT All-Sky Survey (RASS) is used to investigate the X-ray properties of a complete sample of Abell clusters with measured redshifts and accurate positions. The sample comprises the 145 clusters within a 561 square degree region at high galactic latitude. The mean redshift is 0.17. This sample is especially well suited to be studied within the RASS since the mean exposure time is higher than average and the mean galactic column density is very low. These together produce a flux limit of about 4.2 x 10-13 erg/sq cm/s in the 0.5 to 2.5 keV energy band. Sixty-six (46%) individual clusters are detected at a significance level higher than 99.7% of which 7 could be chance coincidences of background or foreground sources. At redshifts greater than 0.3 six clusters out of seven (86%) are detected at the same significance level. The detected objects show a clear X-ray luminosity -- galaxy count relation with a dispersion consistent with other external estimates of the error in the counts. By analyzing the excess of positive fluctuations of the X-ray flux at the cluster positions, compared with the fluctuations of randomly drawn background fields, it is possible to extend these results below the nominal flux limit. We find 80% of richness R greater than or = 0 and 86% of R greater than or = 1 clusters are X-ray emitters with fluxes above 1 x 10-13 erg/sq cm/s. Nearly 90% of the clusters meeting the requirements to be in Abell's statistical sample emit above the same level. We therefore conclude that almost all Abell clusters are real clusters and the Abell catalog is not strongly contaminated by projection effects. We use the Kaplan-Meier product limit estimator to calculate the cumulative X-ray luminosity function. We show that the shape of the luminosity functions are similiar for different richness classes, but the characteristic luminosities of richness 2 clusters are about twice those of richness 1 clusters which are in turn about twice those of richness 0 clusters. This result is another manifestation of the luminosity -- richness elation for Abell clusters.
Briel Ulrich G.
Henry Patrick J.
No associations
LandOfFree
X-ray emission from a complete sample of Abell clusters of galaxies does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with X-ray emission from a complete sample of Abell clusters of galaxies, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and X-ray emission from a complete sample of Abell clusters of galaxies will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-807176