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Description
This table contains a catalog of X-ray luminosities for 401 early-type galaxies (and 24 other galaxies which were listed in previuous studies as early but which have LEDA T-types >= -1.5), of which 136 are based on newly analysed ROSAT PSPC pointed observations. The remaining luminosities are taken from the literature and converted to a common energy band, spectral model and distance scale. In their paper, the authors use this sample to fit the L<sub>X</sub>/L<sub>B</sub> relation for early-type galaxies and find a best-fit slope for the catalog of ~ 2.2. The authors demonstrate the influence of group-dominant galaxies on the fit and present evidence that the relation is not well modeled by a single power-law fit. They also derive estimates of the contribution to galaxy X-ray luminosities from discrete-sources and conclude that they provide L<sub>(discrete-source-contribution)</sub>/L<sub>B</sub> ~ 29.5 erg s<sup>-1</sup>/L<sub>Bsun</sub>. The authors compare this result with luminosities from their catalog. Lastly, they examine the influence of environment on galaxy X-ray luminosity and on the form of the L<sub>X</sub>/L<sub>B</sub> relation. They conclude that although environment undoubtedly affects the X-ray properties of individual galaxies, particularly those in the centres of groups and clusters, it does not change the nature of whole populations. The sample of early-type galaxies was selected from the Lyon-Meudon Extragalactic Data Archive (LEDA). This catalog at that time contained information on ~ 100,000 galaxies, of which ~ 40,000 had redshift and morphological data. Galaxies were selected using the following criteria: (i) Morphological Type T < -1.5 (i.e. E, E-S0 and S0 galaxies). (ii) Virgo-corrected recession velocity V <= 9,000 km s<sup>-1</sup>. (iii) Apparent Magnitude B<sub>T</sub> <= 13.5. The redshift and apparent magnitude restrictions were chosen in order to minimize the effects of incompleteness on their sample. The LEDA catalogue is known to be 90 per cent complete at B<sub>T</sub> = 14.5, so the selection should be close to statistical completeness. The selection process produced ~ 700 objects. The authors then cross-correlated this list with a list of public ROSAT PSPC pointings. Only pointings within 30 arcminutes of the target were accepted, as, further off-axis, the PSPC point-spread function becomes large enough to make analysis problematic. This left 209 galaxies with X-ray data available. The authors also added data from previously published catalogs, ROSAT PSPC All-Sky Survey values from Beuing et al. (1999, MNRAS, 302, 209), and Einstein IPC values from Fabbiano et al. (1992, ApJS, 80, 531) and Roberts et al. (1991, ApJS, 75, 751). These other references use a range of models to fit the data, different wavebands, distances and blue luminosities. O'Sullivan et al. corrected for these differences by converting the catalogs to a common set of values, as used for their own results. All of the X-ray luminosities have been converted to a common format based on a reliable distance scale (assuming H<sub>0</sub> = 75 km s<sup>-1</sup> Mpc<sup>-1</sup>), and correcting for differences in spectral fitting techniques and waveband. This table was created by the HEASARC in October 2010 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/328/461">CDS catalog J/MNRAS/328/461</a> file table3.dat. This is a service provided by NASA HEASARC .
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