371 research outputs found
Black Hole Growth & the M_BH--Bulge Relations
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?
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
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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