SIMBAD references

2001MNRAS.325..693H - Mon. Not. R. Astron. Soc., 325, 693-706 (2001/August-1)

X-ray luminosities of galaxies in groups.


Abstract (from CDS):

We have derived the X-ray luminosities of a sample of galaxies in groups, making careful allowance for contaminating intragroup emission. The LX:LB and LX:LFIR relations of spiral galaxies in groups appear to be indistinguishable from those in other environments, however the elliptical galaxies fall into two distinct classes. The first class is central-dominant group galaxies, which are very X-ray luminous and may be the focus of group cooling flows. All other early-type galaxies in groups belong to the second class, which populates an almost constant band of LX/LB over the range 9.8<logLB<11.3. The X-ray emission from these galaxies can be explained by a superposition of discrete galactic X-ray sources together with a contribution from hot gas lost by stars, which varies a great deal from galaxy to galaxy. In the region where the optical luminosity of the non-central group galaxies overlaps with the dominant galaxies, the dominant galaxies are over an order of magnitude more luminous in X-rays.

We also compared these group galaxies with a sample of isolated early-type galaxies, and used previously published work to derive LX:LB relations as a function of environment. The non-dominant group galaxies have mean LX/LB ratios very similar to those of isolated galaxies, and we see no significant correlation between LX/LB and environment. We suggest that previous findings of a steep LX:LB relation for early-type galaxies result largely from the inclusion of group-dominant galaxies in samples.

Abstract Copyright: The Royal Astronomical Society

Journal keyword(s): galaxies: elliptical and lenticular, cD - galaxies: ISM - galaxies: spiral - X-rays: galaxies

Simbad objects: 210

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