451 research outputs found
Relationship of Black Holes to Bulges
Supermassive black holes appear to be uniquely associated with galactic
bulges. The mean ratio of black hole mass to bulge mass was until recently very
uncertain, with ground based, stellar kinematical data giving a value roughly
an order of magnitude larger than other techniques. The discrepancy was
resolved with the discovery of the M-sigma relation, which simultaneously
established a tight corrrelation between black hole mass and bulge velocity
dispersion, and confirmed that the stellar kinematical mass estimates were
systematically too large due to failure to resolve the black hole's sphere of
influence. There is now excellent agreement between the various techniques for
estimating the mean black hole mass, including dynamical mass estimation in
quiescent galaxies; reverberation mapping in active galaxies and quasars; and
computation of the mean density of compact objects based on integrated quasar
light. Implications of the M-sigma relation for the formation of black holes
are discussed.Comment: 29 pages, 12 postscript figures, uses newpasp.sty. To appear in "The
Central Kpc of Starbursts and AGN", ed. J. H. Knapen, J. E. Beckman, I.
Shlosman & T. J. Mahone
Black Hole Demographics
The purpose of this contribution is to review the current status of black
hole demographics in light of recent advances in the study of high redshift
QSOs (section 2), local AGNs (section 3) and local quiescent galaxies (section
4). I will then outline the prospects for future progress (section 5), and
discuss what I believe will be the challenges for the years to come [ABRIDGED].Comment: Invited talk, to appear in "Current High-Energy Emission around Black
Holes" Proc. 2nd KIAS Astrophysics Workshop held in Seoul, Korea (Sep 3-7
2001) ed. C.-H. Lee. Singapore: World Scientifi
No Supermassive Black Hole in M33?
We analyze optical long-slit spectroscopy of the nucleus of M33 obtained from
the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope.
Rather than the steep rise expected within the radius of influence of a
supermassive black hole, the velocity dispersion drops significantly within the
inner parsec. Dynamical modelling yields an estimated upper limit of 3000 solar
masses for the mass of a central compact object. This upper limit is however
consistent within the uncertainties with the mass predicted by the M-sigma
relation, which is between 2000 and 20,000 solar masses. We therefore can not
conclude that the presence of a massive black hole in the nucleus of M33 would
require a different formation mechanism from that of the black holes detected
in galaxies with more luminous bulges.Comment: 10 pages, 4 postscript figure
Supermassive Black Holes and Their Host Galaxies - I. Bulge luminosities from dedicated near-infrared data
In an effort to secure, refine and supplement the relation between central
Supermassive Black Hole masses (Mbh), and the bulge luminosities of their host
galaxies, (Lbul), we obtained deep, high spatial resolution K-band images of 35
nearby galaxies with securely measured Mbh, using the wide-field WIRCam imager
at the Canada-France-Hawaii-Telescope (CFHT). A dedicated data reduction and
sky subtraction strategy was adopted to estimate the brightness and structure
of the sky, a critical step when tracing the light distribution of extended
objects in the near-infrared. From the final image product, bulge and total
magnitudes were extracted via two-dimensional profile fitting. As a first order
approximation, all galaxies were modeled using a simple Sersic-bulge +
exponential-disk decomposition. However, we found that such models did not
adequately describe the structure that we observe in a large fraction of our
sample galaxies which often include cores, bars, nuclei, inner disks, spiral
arms, rings and envelopes. In such cases, we adopted profile modifications
and/or more complex models with additional components. The derived bulge
magnitudes are very sensitive to the details and number of components used in
the models, although total magnitudes remain almost unaffected. Usually, but
not always, the luminosities and sizes of the bulges are overestimated when a
simple bulge+disk decomposition is adopted in lieu of a more complex model.
Furthermore we found that some spheroids are not well fit when the ellipticity
of the Sersic model is held fixed. This paper presents the details of the image
processing and analysis, while in a companion paper we discuss how
model-induced biases and systematics in bulge magnitudes impact the Mbh-Lbul
relation.Comment: 48 pages, 40 Figures, 5 tables; high-resolution figures and a
corresponding version of the .pdf are available at
https://www.dropbox.com/sh/lx0xqn89wa3y320/2hS-zZ12Y
The Low End of the Supermassive Black Hole Mass Function: Constraining the Mass of a Nuclear Black Hole in NGC 205 via Stellar Kinematics
Hubble Space Telescope (HST) images and spectra of the nucleated dwarf
elliptical galaxy NGC 205 are combined with 3-integral axisymmetric dynamical
models to constrain the mass (M_BH) of a putative nuclear black hole. This is
only the second attempt, after M33, to use resolved stellar kinematics to
search for a nuclear black hole with mass below 10^6 solar masses. We are
unable to identify a best-fit value of M_BH in NGC 205; however, the data
impose a upper limit of 2.2x10^4 M_sun (1sigma confidence) and and upper limit
of 3.8x10^4 M_sun (3sigma confidence). This upper limit is consistent with the
extrapolation of the M_BH-sigma relation to the M_BH < 10^6 M_sunregime. If we
assume that NGC 205 and M33 both contain nuclear black holes, the upper limits
on M_BH in the two galaxies imply a slope of ~5.5 or greater for the M_BH-sigma
relation. We use our 3-integral models to evaluate the relaxation time (T_r)
and stellar collision time (T_coll) in NGC 205; T_r~10^8 yr or less in the
nucleus and T_coll~10^11 yr. The low value of T_r is consistent with core
collapse having already occurred, but we are unable to draw conclusions from
nuclear morphology about the presence or absence of a massive black hole.Comment: Latex emulateapj, 15 pages, 16 figures, Version accepted for
Publication in ApJ, 20 July 2005, v628. Minor changes to discussion
Black Hole Demographics from the M(BH)-sigma Relation
We analyze a sample of 32 galaxies for which a dynamical estimate of the mass
of the hot stellar component, M_bulge, is available. For each of these
galaxies, we calculate the mass of the central black hole, M_BH, using the
tight empirical correlation between M_BH and the bulge stellar velocity
dispersion. The frequency function N(log M_BH/M_bulge) is reasonably well
described as a Gaussian with ~ -2.90 and standard deviation
0.45; the implied mean ratio of black hole to bulge mass is a factor 5 smaller
than generally quoted in the literature. We present marginal evidence for a
lower, average black-hole mass fraction in more massive galaxies. The total
mass density in black holes in the local Universe is estimated to be 5 x 10^5
solar masses per cubic megaparsec, consistent with that inferred from high
redshift (z ~ 2) AGNs.Comment: 12 Latex pages, 4 postscript figure
Observational evidence for a connection between SMBHs and dark matter haloes
We investigate the relation between circular velocity vc and bulge velocity
dispersion sigma in spiral galaxies, based on literature data and new
spectroscopic observations. We find a strong, nearly linear vc-sigma
correlation with a negligible intrinsic scatter, and a striking agreement with
the corresponding relation for elliptical galaxies. The least massive galaxies
(sigma < 80 km/s) significantly deviate from this relation. We combine this
vc-sigma correlation with the well-known MBH-sigma relation to obtain a tight
correlation between circular velocity and supermassive black hole mass, and
interpret this as observational evidence for a close link between supermassive
black holes and the dark matter haloes in which they presumably formed. Apart
from being an important ingredient for theoretical models of galaxy formation
and evolution, the relation between MBH and circular velocity has the potential
to become an important practical tool in estimating supermassive black hole
masses in spiral galaxies.Comment: 4 pages, 1 figure, 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
Supermassive Black Holes and Their Host Galaxies - II. The correlation with near-infrared luminosity revisited
We present an investigation of the scaling relations between Supermassive
Black Hole (SMBH) masses (Mbh), and their host galaxies' K-band bulge (Lbul)
and total (Ltot) luminosities. The wide-field WIRCam imager at the
Canada-France-Hawaii-Telescope (CFHT) was used to obtain the deepest and
highest resolution near infrared images available for a sample of 35 galaxies
with securely measured Mbh, selected irrespective of Hubble type. For each
galaxy, we derive bulge and total magnitudes using a two-dimensional image
decomposition code that allows us to account, if necessary, for large- and
small-scale disks, cores, bars, nuclei, rings, envelopes and spiral arms. We
find that the present-day Mbh-Lbul and Mbh-Ltot relations have consistent
intrinsic scatter, suggesting that Mbh correlates equally well with bulge and
total luminosity of the host. Our analysis provides only mild evidence of a
decreased scatter if the fit is restricted to elliptical galaxies. The
log-slopes of the Mbh-Lbul and Mbh-Ltot relations are 0.75+/-0.10 and
0.92+/-0.14, respectively. However, while the slope of the Mbh-Lbul relation
depends on the detail of the image decomposition, the characterization of
Mbh-Ltot does not. Given the difficulties and ambiguities of decomposing galaxy
images into separate components, our results indicate that Ltot is more
suitable as a tracer of SMBH mass than Lbul, and that the Mbh-Ltot relation
should be used when studying the co-evolution of SMBHs and galaxies.Comment: 19 pages, 3 figures, 7 table
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