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 log LSX,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 or intermediate 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.