2010/11/08 by Robert A. Crain, Crain, Robert A., Ian G. McCarthy +7
Physics and Astronomy · #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #astro-ph.CO #astro-ph.HE
paper · pdf · doi:10.48550/arxiv.1011.1906
8 pages, 3 figures. Submitted to MNRAS. Comments welcome
arxiv created 2010/11/08 · arxiv updated 2010/11/10
The existence of hot, X-ray luminous gaseous coronae surrounding present day L* galaxies is a generic prediction of galaxy formation theory in the cold dark matter cosmogony. While extended X-ray emission has been known to exist around elliptical galaxies for a long time, diffuse extra-planar emission has only recently been detected around disc galaxies. We compile samples of elliptical and disc galaxies that have Chandra and XMM-Newton measurements, and compare the scaling of the coronal X-ray luminosity (LX) with both the K-band luminosity (LK) and the coronal X-ray temperature (TX). The X-ray flux measurements are corrected for non-thermal point source contamination by spatial excision and spectral subtraction for resolved and unresolved sources respectively. We find that the properties of the extended X-ray emission from galaxies of different morphological types are similar: for both elliptical and disc galaxies, the LX - LK and LX - TX relations have similar slope, normalisation and scatter. The observed universality of coronal X-ray properties suggests that the bulk of this emission originates from gas that has been accreted, shock-heated and compressed during the assembly of the galaxy and that outflows triggered by stellar processes make only a minor contribution to the X-ray emission. This reservoir of cooling gas is a potential source of morphological transformation; it provides a fresh supply of material for discs to grow around galaxies of all morphological types.