NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-05-20 T20:30:24 PDT
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For refcode 2005MNRAS.364..169P:
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Copyright by Royal Astronomical Society. 2005MNRAS.364..169P The X-ray emission properties and the dichotomy in the central stellar cusp shapes of early-type galaxies Pellegrini, S. Abstract. 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 (L_SX,tot_), which is a measure of the galactic hot gas content, and their nuclear hard emission (L_HX,nuc_), mostly coming from Chandra observations, which is a measure of the nuclear activity. At any optical luminosity, the highest L_SX,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 logL_SX,tot_ (ergs^-1^) >~ 41.5 cases. The highest L_HX,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, L_HX,nuc_ is independent of the central stellar profile shape. The presence of optical nuclei (also found by HST) is unrelated to the level of L_HX,nuc_, even though the highest L_HX,nuc_ are all associated with optical nuclei. The implications of these findings for galaxy evolution and accretion modalities at the present epoch are discussed. Key words: galaxies: elliptical and lenticular, cD, galaxies: evolution, galaxies: fundamental parameters, galaxies: nuclei, X-rays: galaxies, X-rays: ISM
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