The X-ray emission properties and the dicothomy in the central stellar cusp shapes of early-type galaxies

Hubble Space Telescope revealed a dicothomy in the central surface brightness profiles of early-type galaxies, that subsequently have been grouped into two families: core, boxy, anisotropic systems and cuspy ("power law"), disky, rotating ones. Here we investigate whether a dicothomy is present also in the X-ray properties of the two families. We consider both their total soft emission (Lsx,tot), that is a measure of the galactic hot gas content, and their nuclear hard emission (Lhx,nuc), mostly coming from Chandra observations, that is a measure of the nuclear activity. At any optical luminosity, the highest Lsx,tot values are reached by core galaxies; this is explained with their being 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 AGNs, in this sample are hosted only by core galaxies; at low luminosity AGN levels, Lhx,nuc is independent of the central stellar profile shape. The presence of optical nuclei (also found by HST) is unrelated with the level of Lhx,nuc, even though the highest Lhx,nuc are all associated with optical nuclei. The implications of these findings for the galaxy evolution and the accretion modalities at the present epoch are discussed.