NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2018-11-17 T09:31:02 PST
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For refcode 1994ApJ...436...44E:
Retrieve 23 NED objects in this reference.
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Copyright by American Astronomical Society. Reproduced by permission
1994ApJ...436...44E X-RAY EMISSION FROM HICKSON'S COMPACT GROUPS OF GALAXIES: RESULTS FROM THE ROSAT ALL-SKY SURVEY HARALD EBELING, WOLFGANG VOGES, AND HANS BOHRINGER Max-Planck-Institut fur Extraterrestrische Physik, D-85740 Garching bei Munchen, Germany Received 1994 February 16; accepted 1994 May 26 ABSTRACT We report on the detection of X-ray emission from 11 of Hickson's compact groups of galaxies (HCGs) in the ROSAT All-Sky Survey (RASS). One of these is clearly part of a much richer system with an X-ray luminosity comparable to that of Abell clusters. With two other detections, the X- ray emission is dominated by pointlike and spectrally soft sources which can be identified with active galactic nuclei within the group. The remaining eight detections constitute the first statistically relevant sample of compact groups of galaxies truly seen in X-rays. Some of the sources are clearly extended; for the other ones it is, at the sensitivity of the RASS, not clear whether the X-ray emission is due to the presence of a hot intragroup gas, to individual galaxies, or to galaxy-galaxy interactions in these objects, although the former is suggested by the hardness of the emission typical of a thermal bremsstrahlung spectrum with T_gas_1 keV. We find the HCG's X-ray luminosity to be almost independent of the optical richness of the group; however, there seems to be a strong correlation with the spiral fraction and the morphological type of the dominant galaxy. A comparison between the X-ray luminosity functions (XLFs) of HCGs and clusters of galaxies suggests that, at X-ray luminosities of some 10^42^ h_50_^-2^ ergs s^-1^, compact groups of galaxies contribute at the ~10% level to the XLF of galactic systems. The majority of the latter thus have to be loose groups and poor clusters of galaxies. Subject headings: galaxies: clustering - galaxies: interactions - X-rays: galaxies
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