371 research outputs found

    Black Hole Growth & the M_BH--Bulge Relations

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    We present the black hole mass--bulge velocity dispersion relation for a complete sample of 75 soft X-ray selected AGNs. We find that the AGNs with highest accretion rates relative to Eddington lie below the \mbh--\sig\ relation of broad line Seyfert 1s, confirming the Mathur et al (2001) result. The statistical result is robust and not due to any systematic measurement error. This has important consequences towards our understanding of black hole formation and growth: black holes grow by accretion in well formed bulges. As they grow, they get closer to the \mbh--\sig relation for normal galaxies. The accretion is highest in the beginning and dwindles as time goes by. Our result does not support theories of the \mbh--\sig relation in which the black hole mass is a constant fraction of the bulge mass/ velocity dispersion {\it at all times} or those in which bulge growth is controlled by AGN feedback.Comment: To appear in "The Interplay among Black Holes, Stars and ISM in Galactic Nuclei", IAU Symposium 222, Eds.: Th. Storchi Bergmann, L.C. Ho & H.R. Schmit

    The z=5.8 Quasar SDSSp J1044-0125: A Peek at Quasar Evolution?

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    The newly discovered z=5.8 quasar SDSSp J104433.04-012502.2 was recently detected in X-rays and found to be extremely X-ray weak. Here we present the hardness ratio analysis of the XMM-Newton observation. We consider various models to explain the detection in the soft X-ray band and non-detection in the hard band, together with its X-ray weakness. We show that the source may have a steep power-law slope, with an absorber partially covering the continuum. This may be X-ray evidence to support the argument of Mathur (2000) that narrow line Seyfert 1 galaxies, which show steep power-law slopes, might be the low redshift, low luminosity analogues of the high redshift quasars. Heavily shrouded and steep X-ray spectrum quasars may indeed represent the early stages of quasar evolution (Mathur 2000, Fabian 1999) and SDSSp J104433.04-012502.2 is possibly giving us a first glimpse of the physical evolution of quasar properties.Comment: To appear in A

    GALEX Measurements of the Big Blue Bump in Soft X-ray Selected AGN

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    We study the UV properties of Type I AGN from the ROSAT All-Sky Survey that have been selected to show unusually soft X-ray continua. We examine a sample of 54 Seyfert 1 galaxies with detections in both Near-UV and Far-UV bands of the Galaxy Evolution Explorer (GALEX) satellite. Our sample is systematically fainter in the UV than galaxies studied in similar work by previous authors. We look for correlations between their UV and X-ray properties as well as correlations of these properties with either black hole mass or Eddington ratio. The shape of the Big Blue Bump(BBB) in the GALEX regime does not appear to correlate with its strength relative to the power law continuum, which conflicts with results reported by previous authors. The strength of the BBB is correlated with the shape of the X-ray continuum, in agreement with previous work, but the slope of the correlation is different than previously reported. The properties of the accretion disks of Type I AGN in the GALEX regime are relatively independent of black hole mass and Eddington ratio. We compare our measurements to the predictions of alternative theories for the origin of the soft excess, but we are unable to distinguish between Comptonization of BBB photons by a hot plasma and absorption in relativistic winds as the most likely origins for the soft X-ray excess.Comment: 42 pages, 15 figures. Accepted by Ap
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