1,300 research outputs found
The largest black holes and the most luminous galaxies
The empirical relationship between the broad line region size and the source
luminosity in active galactic nuclei (AGNs) is used to obtain black holes (BH)
masses for a large number of quasars in three samples. The largests BH masses
found exceed 10^{10} Msun and are correlated, almost linearly, with the source
luminosity. Such BH masses, when converted to galactic bulge mass and
luminosity, indicate masses in excess of 10^{13} Msun and sigma(*) in excess of
700 km/sec. Such massive galaxies have never been observed. The largest BHs
reside, almost exclusively, in high redshift quasars. This, and the deduced BH
masses, suggest that several scenarios of BH and galaxy formation are
inconsistent with the observations. Either the observed size-L relationship in
low luminosity AGNs does not extend to very high luminosity or else the
M(BH)-M_B(bulge)-sigma(*) correlations observed in the local universe do not
reflect the relations of those quantities at the epoch of galaxy formation.Comment: 12 pages, 2 figures, one table, submitted to ApJ
Supermassive black holes do not correlate with dark matter halos of galaxies
Supermassive black holes have been detected in all galaxies that contain
bulge components when the galaxies observed were close enough so that the
searches were feasible. Together with the observation that bigger black holes
live in bigger bulges, this has led to the belief that black hole growth and
bulge formation regulate each other. That is, black holes and bulges
"coevolve". Therefore, reports of a similar correlation between black holes and
the dark matter halos in which visible galaxies are embedded have profound
implications. Dark matter is likely to be nonbaryonic, so these reports suggest
that unknown, exotic physics controls black hole growth. Here we show - based
in part on recent measurements of bulgeless galaxies - that there is almost no
correlation between dark matter and parameters that measure black holes unless
the galaxy also contains a bulge. We conclude that black holes do not correlate
directly with dark matter. They do not correlate with galaxy disks, either.
Therefore black holes coevolve only with bulges. This simplifies the puzzle of
their coevolution by focusing attention on purely baryonic processes in the
galaxy mergers that make bulges.Comment: 12 pages, 9 Postscript figures, 1 table; published in Nature (20
January 2011
Which Globular Clusters contain Intermediate-mass Black Holes?
It has been assumed that intermediate-mass black holes (IMBHs) in globular
clusters can only reside in the most centrally concentrated clusters, with a
so-called `core-collapsed' density profile. While this would be a natural
guess, it is in fact wrong. We have followed the evolution of star clusters
containing IMBHs with masses between 125 \le M_{BH} \le 1000 M_{\odot} through
detailed N-body simulations, and we find that a cluster with an IMBH, in
projection, appears to have a relatively large `core' with surface brightness
only slightly rising toward the center. This makes it highly unlikely that any
of `core-collapsed' clusters will harbor an IMBH. On the contrary, the places
to look for an IMBH are those clusters that can be fitted well by
medium-concentration King models.
The velocity dispersion of the visible stars in a globular cluster with an
IMBH is nearly constant well inside the apparent core radius. For a cluster of
mass M_C containing an IMBH of mass M_{BH}, the influence of the IMBH becomes
significant only at a fraction 2.5 M_{BH}/M_C of the half-mass radius, deep
within the core, where it will affect only a small number of stars. In
conclusion, observational detection of an IMBH may be possible, but will be
challenging.Comment: 13 pages, 3 figures, Accepted ofr publication in ApJ (scheduled for
February 2005
Towards a Comprehensive Fueling-Controlled Theory on the Growth of Massive Black Holes and Host Spheroids
We study the relation between nuclear massive black holes and their host
spheroid gravitational potential. Using AMR numerical simulations, we analyze
how gas is transported in the nuclear (central kpc) regions of galaxies. We
study the gas fueling onto the inner accretion disk (sub-pc scale) and the star
formation in a massive nuclear disk like those generally found in
proto-spheroids (ULIRGs, SCUBA Galaxies). These sub-pc resolution simulation of
gas fueling that is mainly depleted by star formation naturally satisfy the
`M_BH - $M_virial' relation, with a scatter considerably less than the observed
one. We found a generalized version of Kennicutt-Schmidt Law for starbursts is
satisfied, in which the total gas depletion rate (dot{M}_gas = dot{M}_BH +
dot{M}_SF) is the one that scales as M_gas/t_orbital. We also found that the
`M_BH - sigma' relation is a byproduct of the `M_BH - M_virial' relation in the
fueling controlled scenario.Comment: 12 pages, figures, submited to ApJ, email: [email protected]
Production and Evolution of Perturbations of Sterile Neutrino Dark Matter
Sterile neutrinos, fermions with no standard model couplings [SU(2)
singlets], are predicted by most extensions of the standard model, and may be
the dark matter. I describe the nonthermal production and linear perturbation
evolution in the early universe of this dark matter candidate. I calculate
production of sterile neutrino dark matter including effects of Friedmann
dynamics dictated by the quark-hadron transition and particle population, the
alteration of finite temperature effective mass of active neutrinos due to the
presence of thermal leptons, and heating of the coupled species due to the
disappearance of degrees of freedom in the plasma. These effects leave the
sterile neutrinos with a non-trivial momentum distribution. I also calculate
the evolution of sterile neutrino density perturbations in the early universe
through the linear regime and provide a fitting function form for the transfer
function describing the suppression of small scale fluctuations for this warm
dark matter candidate. The results presented here differ quantitatively from
previous work due to the inclusion here of the relevant physical effects during
the production epoch.Comment: v4: matches version in Phys. Rev.
The Relation between Black Hole Mass, Bulge Mass, and Near-Infrared Luminosity
We present new accurate near-infrared (NIR) spheroid (bulge) structural
parameters obtained by two-dimensional image analysis for all galaxies with a
direct black hole (BH) mass determination. As expected, NIR bulge luminosities
Lbul and BH masses are tightly correlated, and if we consider only those
galaxies with secure BH mass measurement and accurate Lbul (27 objects), the
spread of MBH-Lbul is similar to MBH-sigma, where sigma is the effective
stellar velocity dispersion. We find an intrinsic rms scatter of ~0.3 dex in
log MBH. By combining the bulge effective radii R_e measured in our analysis
with sigma, we find a tight linear correlation (rms ~ 0.25 dex) between MBH and
the virial bulge mass (propto R_e sigma^2), with ~ 0.002. A partial
correlation analysis shows that MBH depends on both sigma and R_e, and that
both variables are necessary to drive the correlations between MBH and other
bulge properties.Comment: Astrophysical Journal Letters, in pres
Do Globular Clusters Harbor Black Holes?
It has been firmly established that there exists a tight correlation between
the central black hole mass and velocity dispersion (or luminosity) of
elliptical galaxies, ``pseudobulges'' and bulges of galaxies, although the
nature of this correlation still remains unclear. In this letter, we explore
the possibility of extrapolating such a correlation to less massive, spherical
systems like globular clusters. In particular, motivated by the apparent
success in globular cluster M15, we present an estimate of the central black
hole mass for a number of globular clusters with available velocity dispersion
in the literature.Comment: 6 pages, 2 figures, 1 table; accepted for publication in CJA
The black hole mass versus velocity dispersion relation in QSOs/Active Galactic Nuclei: observational appearance and black hole growth
Studies of massive black holes (BHs) in nearby galactic centers have revealed
a tight correlation between BH mass and galactic velocity dispersion. In this
paper we investigate how the BH mass versus velocity dispersion relation and
the nuclear luminosity versus velocity dispersion relation in QSOs/active
galactic nuclei (AGNs) are connected with the BH mass versus velocity
dispersion relation in local galaxies, through the nuclear luminosity evolution
of individual QSOs/AGNs and the mass growth of individual BHs. In the study we
ignore the effects of BH mergers and assume that the velocity dispersion does
not change significantly during and after the nuclear activity phase. Using the
observed correlation in local galaxies and an assumed form of the QSO/AGN
luminosity evolution and BH growth, we obtain the simulated observational
appearance of the BH mass versus velocity dispersion relation in QSOs/AGNs. The
simulation results illustrate how the BH accretion history (e.g., the lifetime
of nuclear activity and the possibility that QSOs/AGNs accrete at a
super-Eddington accretion rate at the early evolutionary stage) can be inferred
from the difference between the relation in QSOs/AGNs and that in local
galaxies. We also show how the difference may be weakened by the flux limit of
telescopes. We expect that a large complete sample of QSOs/AGNs with accurate
BH mass and velocity dispersion measurements will help to quantitatively
constrain QSO/AGN luminosity evolution and BH growth models.Comment: 20 pages, including 4 figures; revised to match the published versio
The structure of the central disk of NGC 1068: a clumpy disk model
NGC 1068 is one of the best studied Seyfert II galaxies, for which the
blackhole mass has been determined from the Doppler velocities of water maser.
We show that the standard -disk model of NGC 1068 gives disk mass
between the radii of 0.65 pc and 1.1 pc (the region from which water maser
emission is detected) to be about 7x10 M (for ), more
than four times the blackhole mass, and a Toomre Q-parameter for the disk is
0.001. This disk is therefore highly self-gravitating and is subject to
large-amplitude density fluctuations. We conclude that the standard
-viscosity description for the structure of the accretion disk is
invalid for NGC 1068.
In this paper we develop a new model for the accretion disk. The disk is
considered to be composed of gravitationally bound clumps; accretion in this
clumped disk model arises because of gravitational interaction of clumps with
each other and the dynamical frictional drag exerted on clumps from the stars
in the central region of the galaxy. The clumped disk model provides a
self-consistent description of the observations of NGC 1068. The computed
temperature and density are within the allowed parameter range for water maser
emission, and the rotational velocity in the disk falls off as .Comment: To appear in Ap
The Accuracy of Morphological Decomposition of Active Galactic Nucleus Host Galaxies
In order to assess the accuracy with which we can determine the morphologies
of AGN host galaxies, we have simulated more than 50,000 ACS images of galaxies
with z < 1.25, using image and noise properties appropriate for the GOODS
survey. We test the effect of central point-source brightness on host galaxy
parameter recovery with a set of simulated AGN host galaxies made by adding
point sources to the centers of normal galaxies. We extend this analysis and
also quantify the recovery of intrinsic morphological parameters of AGN host
galaxies with a set of fully simulated inactive and AGN host galaxies.
We can reliably separate good from poor fit results using a combination of
reasonable error cuts, in the regime where L_{host}:L_{PS} > 1:4. We give
quantitative estimates of parameter errors as a function of
host-to-point-source ratio. In general, we separate host and point-source
magnitudes reliably at all redshifts; point sources are well recovered more
than 90% of the time, although spurious detection of central point sources can
be as high as 25% for bulge-dominated sources. We find a general correlation
between Sersic index and intrinsic bulge-to-total ratio, such that a host
galaxy with Sersic n < 1.5 generally has at least 80% of its light from a disk
component. Likewise, "bulge-dominated" galaxies with n > 4 typically derive at
least 70% of their total host galaxy light from a bulge, but this number can be
as low as 55%. Single-component Sersic fits to an AGN host galaxy are
statistically very reliable to z < 1.25 (for ACS survey data like ours). In
contrast, two-component fits involving separate bulge and disk components tend
to over-estimate the bulge fraction by ~10%, with uncertainty of order 50%.Comment: 45 pages, 20 figures, submitted to ApJ ; Accepted Version --
additions to introduction and conclusions; title changed, was "Simulations of
AGN Host Galaxy Morphologies
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