Mon. Not. R. Astron. Soc., 364, 169-178 (2005/November-3)
The X-ray emission properties and the dichotomy in the central stellar cusp shapes of early-type galaxies.
Abstract (from CDS):
The Hubble Space Telescope has revealed a dichotomy in the central surface brightness profiles of early-type galaxies, which have subsequently been grouped into two families: core, boxy, anisotropic systems; and cuspy (`power-law'), discy, rotating ones. Here we investigate whether a dichotomy is also present in the X-ray properties of the two families. We consider both their total soft emission (LSX,tot), which is a measure of the galactic hot gas content, and their nuclear hard emission (LHX,nuc), mostly coming from Chandra observations, which is a measure of the nuclear activity. At any optical luminosity, the highest LSX,tot values are reached by core galaxies; this is explained by their being the central dominant galaxies of groups, subclusters or clusters, in many of the logLSX,tot(erg/s) ≳ 41.5 cases. The highest LHX,nuc values, similar to those of classical active galactic nuclei (AGNs), in this sample are hosted only by core or intermediate galaxies; at low luminosity AGN levels, LHX,nucis independent of the central stellar profile shape. The presence of optical nuclei (also found by HST) is unrelated to the level of LHX,nuc, even though the highest LHX,nuc are all associated with optical nuclei. The implications of these findings for galaxy evolution and accretion modalities at the present epoch are discussed.
2005 The Author. Journal compilation © 2005 RAS
galaxies: elliptical and lenticular, cD - galaxies: evolution - galaxies: fundamental parameters - galaxies: nuclei - X-rays: galaxies - X-rays: ISM
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