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Date and Time of the Query: 2019-05-23 T07:26:15 PDT
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For refcode 2010ApJ...717..640P:
Retrieve 112 NED objects in this reference.
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Copyright by American Astronomical Society. Reproduced by permission
2010ApJ...717..640P The Nuclear X-ray Emission of Nearby Early-type Galaxies Pellegrini, S. Abstract. Nuclear hard X-ray luminosities (L_X,nuc_) for a sample of 112 early-type galaxies within a distance of 67 Mpc are used to investigate their relationship with the central galactic black hole mass M_BH_ (coming from direct dynamical studies or the M_BH_-{sigma} relation), the inner galactic structure (using the parameters describing its cuspiness), the hot gas content, and the core radio luminosity. For this sample, L_X,nuc_ ranges from 10^38^ to 10^42^ erg s^-1^, and the Eddington ratio L_X,nuc_/L_Edd_ from 10^-9^ to 10^-4^, with the largest values belonging to four Seyfert galaxies. Together with a trend for L_X,nuc_ to increase on average with the galactic luminosity L_B_ and M_BH_, there is a wide variation of L_X,nuc_ (and L_X,nuc_/L_Edd_), by up to 4 orders of magnitude, at any fixed L_B_ > 6 x 10^9^ L_ B,sun_ or M_BH_ > 10^7^ M_sun_. This large observed range should reflect a large variation of the mass accretion rate M^.^_BH_, and possible reasons for this difference are searched for. On the circumnuclear scale, in a scenario where accretion is (quasi) steady, M^.^_BH_ at fixed L_B_ (or M_BH_) could vary due to differences in the fuel production rate from stellar mass return linked to the inner galactic structure; a trend of L_X,nuc_ with cuspiness is not observed, though, while a tendency for L_X,nuc_/L_Edd_ to be larger in cuspier galaxies is present. In fact, M^.^_BH_ Is predicted to vary with cuspiness by a factor exceeding a few only in hot gas-poor galaxies and for large differences in the core radius; for a subsample with these characteristics the expected effect seems to be present in the observed L_X,nuc_ values. L_X,nuc_ does not show a dependence on the age of the stellar population in the central galactic region, for ages >3 Gyr; less luminous nuclei, though, are found among the youngest galaxies or galaxies with a younger stellar component. On the global galactic scale, L_X,nuc_ shows a trend with the total galactic hot gas cooling rate (L_ X,ISM_): it is detected both in gas-poor and gas-rich galaxies, and on average increases with L_ X,ISM_, but again with a large scatter. The observed lack of a tight relationship between L_X,nuc_ and the circumnuclear and total gas content can be explained if accretion is regulated by factors overcoming the importance of fuel availability, as (1) the gas is heated by black hole feedback and M^.^_BH_ varies due to an activity cycle, and (2) the mass effectively accreted by the black hole can be largely reduced with respect to that entering the circumnuclear region, as in radiatively inefficient accretion with winds/outflows. Finally, differently from L_X,nuc_, the central 5 GHz VLA luminosity shows a clear trend with the inner galactic structure that is similar to that shown by the total soft X-ray emission; therefore, it is suggested that they could both be produced by the hot gas. Key words: galaxies: elliptical and lenticular, cD, galaxies: fundamental parameters, galaxies: nuclei, X-rays: galaxies, X-rays: ISM
Retrieve 112 NED objects in this reference.
Please click here for ADS abstract

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