Home OALib Journal OALib PrePrints Submit Ranking News My Lib FAQ About Us Follow Us+
 Title Keywords Abstract Author All
Search Results: 1 - 10 of 100 matches for " "
 Amri Wandel Physics , 2001, DOI: 10.1086/338134 Abstract: Massive Black Holes detected in the centers of many nearby galaxies show an approximately linear relation with the luminosity of the host bulge, with the black hole mass being 0.001-0.002 of the bulge mass. Previous work suggested that black holes of active (Seyfert 1) galaxies follow a similar relation, but apparently with a significantly lower value of $M_{\rm BH}/M_{\rm bulge}$ (Wandel 1999). New data show that this difference was mainly due to overestimating the black hole mass in quiescent galaxies and overestimating the bulge magnitude of Seyfert galaxies. Using new and updated data we show that AGNs (Seyfert galaxies and quasars) follow the same BH-bulge relation as ordinary (inactive) galaxies. We derive the BH-bulge relation for a sample of 55 AGNs and 35 quiescent galaxies, finding that broad line AGNs have an average black hole/bulge mass fraction of $\sim 0.0015$ with a strong correlation (Mbh ~ Lbulge^{0.9\pm 0.16}). This BH-bulge relation is consistent with the BH-bulge relation of quiescent galaxies and much tighter than previous results. Narrow line AGNs appear to have a lower ratio, Mbh/Mbulge ~ 10^{-4}-10^{-3}. We find this to be a more general feature, the BH/bulge ratio in AGNs being inversely correlated with the emission-line width, implying a strong linear relation between the size of the broad emission line region and the luminosity of the bulge. Finally, combining AGNs with observed and estimated stellar velocity dispersion, we find a significant correlation (Mbh ~ v^{3.5-5}), consistent with that of quiescent galaxies.
 Physics , 1996, DOI: 10.1093/mnras/283.4.111 Abstract: It is believed that most giant elliptical galaxies possess nuclear black holes with masses in excess of $10^8\Msun$. Bondi accretion from the interstellar medium might then be expected to produce quasar-like luminosities from the nuclei of even quiescent elliptical galaxies. It is a puzzle that such luminosities are not observed. Motivated by this problem, Fabian & Rees have recently suggested that the final stages of accretion in these objects occurs in an advection-dominated mode with a correspondingly small radiative efficiency. Despite possessing a long-known active nucleus and dynamical evidence for a black hole, the low radiative and kinetic luminosities of the core of M87 provide the best illustration of this problem. We examine an advection-dominated model for the nucleus of M87 and show that accretion at the Bondi rate is compatible with the best known estimates for the core flux from radio through to X-ray wavelengths. The success of this model prompts us to propose that FR-I radio galaxies and quiescent elliptical galaxies accrete in an advection dominated mode whereas FR-II type radio-loud nuclei possess radiatively efficient thin accretion disks.
 Physics , 2015, DOI: 10.1088/2041-8205/800/1/L10 Abstract: We investigate the co-evolution of black-hole-accretion-rate (BHAR) and star-formation-rate (SFR) in 1.5  Physics , 2012, DOI: 10.1093/mnras/stt074 Abstract: It is strongly believed that Andromeda's double nucleus signals a disk of stars revolving around its central super-massive black hole on eccentric Keplerian orbits with nearly aligned apsides. A self-consistent stellar dynamical origin for such apparently long-lived alignment has so far been lacking, with indications that cluster self-gravity is capable of sustaining such lopsided configurations if and when stimulated by external perturbations. Here, we present results of N-body simulations which show unstable counter-rotating stellar clusters around super-massive black holes saturating into uniformly precessing lopsided nuclei. The double nucleus in our featured experiment decomposes naturally into a thick eccentric disk of apo-apse aligned stars which is embedded in a lighter triaxial cluster. The eccentric disk reproduces key features of Keplerian disk models of Andromeda's double nucleus; the triaxial cluster has a distinctive kinematic signature which is evident in HST observations of Andromeda's double nucleus, and has been difficult to reproduce with Keplerian disks alone. Our simulations demonstrate how the combination of eccentric disk and triaxial cluster arises naturally when a star cluster accreted over a pre-existing and counter-rotating disk of stars, drives disk and cluster into a mutually destabilizing dance. Such accretion events are inherent to standard galaxy formation scenarios. They are here shown to double stellar black hole nuclei as they feed them.  Physics , 2014, DOI: 10.1088/0004-637X/801/1/38 Abstract: Narrow-line Seyfert 1 galaxies (NLS1s) are arguably one of the key AGN subclasses in investigating the origin of the black hole mass - stellar velocity dispersion (M-sigma) relation because of their high accretion rate and significantly low black hole mass. Currently, it is under discussion whether present-day NLS1s offset from the M-sigma relation. Using the directly measured stellar velocity dispersion of 93 NLS1s at z<0.1, and black hole mass estimates based on the updated mass estimators, we investigate the M-sigma relation of NLS1s in comparison with broad-line AGNs. We find no strong evidence that the NLS1s deviates from the M-sigma relation, which is defined by reverberation-mapped type 1 AGNs and quiescent galaxies. However, there is a clear trend of the offset with the host galaxy morphology, i.e., more inclined galaxies toward the line-of-sight have higher stellar velocity dispersion, suggesting that the rotational broadening plays a role in measuring stellar velocity dispersion based on the single-aperture spectra from the Sloan Digital Sky Survey. In addition, we provide the virial factor log f =0.05 \pm 0.12$(f = 1.12), for black hole mass estimators based on the FWHM of H$\beta\$, by jointly fitting the M-sigma relation using quiescent galaxies and reverberation-mapped AGNs.