55,115 research outputs found
On the Correlations between Galaxy Properties and Supermassive Black Hole Mass
We use a large sample of upper limits and accurate estimates of supermassive
black holes masses coupled with libraries of host galaxy velocity dispersions,
rotational velocities and photometric parameters extracted from Sloan Digital
Sky Survey i-band images to establish correlations between the SMBH and host
galaxy parameters. We test whether the mass of the black hole, MBH, is
fundamentally driven by either local or global galaxy properties. We explore
correlations between MBH and stellar velocity dispersion sigma, bulge
luminosity, bulge mass Sersic index, bulge mean effective surface brightness,
luminosity of the galaxy, galaxy stellar mass, maximum circular velocity Vc,
galaxy dynamical and effective masses. We verify the tightness of the MBH-sigma
relation and find that correlations with other galaxy parameters do not yield
tighter trends. We do not find differences in the MBH-sigma relation of barred
and unbarred galaxies. The MBH-sigma relation of pseudo-bulges is also coarser
and has a different slope than that involving classical bulges. The MBH-bulge
mass is not as tight as the MBH-sigma relation, despite the bulge mass proving
to be a better proxy of MBH than bulge luminosity. We find a rather poor
correlation between MBH and Sersic index suggesting that MBH is not related to
the bulge light concentration. The correlations between MBH and galaxy
luminosity or mass are not a marked improvement over the MBH sigma relation. If
Vc is a proxy for the dark matter halo mass, the large scatter of the MBH-Vc
relation then suggests that MBH is more coupled to the baryonic rather than the
dark matter. We have tested the need for a third parameter in the MBH scaling
relations, through various linear correlations with bulge and galaxy
parameters, only to confirm that the fundamental plane of the SMBH is mainly
driven by sigma, with a small tilt due to the effective radius. (Abridged)Comment: 32 pages, 18 figures, 6 tables, accepted for publication in MNRA
Very large scale correlations in the galaxy distribution
We characterize galaxy correlations in the Sloan Digital Sky Survey by
measuring several moments of galaxy counts in spheres. We firstly find that the
average counts grows as a power-law function of the distance with an exponent
D= 2.1+- 0.05 for r in [0.5,20] Mpc/h and D = 2.8+-0.05 for r in [30,150]
Mpc/h. In order to estimate the systematic errors in these measurements we
consider the counts variance finding that it shows systematic finite size
effects which depend on the samples sizes. We clarify, by making specific
tests, that these are due to galaxy long-range correlations extending up to the
largest scales of the sample. The analysis of mock galaxy catalogs, generated
from cosmological N-body simulations of the standard LCDM model, shows that for
r<20 Mpc/h the counts exponent is D~2.0, weakly dependent on galaxy luminosity,
while D=3 at larger scales. In addition, contrary to the case of the observed
galaxy samples, no systematic finite size effects in the counts variance are
found at large scales, a result that agrees with the absence of large scale,
r~100 Mpc/h, correlations in the mock catalogs. We thus conclude that the
observed galaxy distribution is characterized by correlations, fluctuations and
hence structures, which are larger, both in amplitude and in spatial extension,
than those predicted by the standard model LCDM of galaxy formation.Comment: 6 pages, 7 figures to be published in Europhysics Letter
Theoretical Estimates of Intrinsic Galaxy Alignment
It has recently been argued that the observed ellipticities of galaxies may
be determined at least in part by the primordial tidal gravitational field in
which the galaxy formed. Long-range correlations in the tidal field could thus
lead to an ellipticity-ellipticity correlation for widely separated galaxies.
We present a new model relating ellipticity to angular momentum, which can be
calculated in linear theory. We use this model to calculate the angular power
spectrum of intrinsic galaxy shape correlations. We show that for low redshift
galaxy surveys, our model predicts that intrinsic correlations will dominate
correlations induced by weak lensing, in good agreement with previous
theoretical work and observations. We find that our model produces `E-mode'
correlations enhanced by a factor of 3.5 over B-modes on small scales, making
it harder to disentangle intrinsic correlations from those induced by weak
gravitational lensing.Comment: 14 pages, 2 figures, MNRAS in press. Error corrected in lensing
calculation; revised versio
Power Spectra for Galaxy Shape Correlations
It has recently been argued that the observed ellipticities of galaxies may
be determined at least in part by the primordial tidal gravitational field in
which the galaxy formed. Long-range correlations in the tidal field could thus
lead to an ellipticity-ellipticity correlation for widely separated galaxies. I
present results of a calculation of the angular power spectrum of intrinsic
galaxy shape correlations using a new model relating ellipticity to angular
momentum. I show that for low redshift galaxy surveys, the model predicts that
intrinsic correlations will dominate correlations induced by weak lensing, in
good agreement with previous theoretical work and observations. The model also
produces `E-mode' correlations enhanced by a factor of 3.5 over `B-modes' on
small scales, making it harder to disentangle intrinsic correlations from weak
lensing.Comment: 4 pages, 1 figure. in ``The Shapes of Galaxies and Their Dark
Halos,'' Yale Cosmology Workshop, Ed. P. Natarajan (New Haven CT, May 2001).
Revised web version corrects lensing curve normalisation in fig.1; text as
publishe
Analytic model for galaxy and dark matter clustering
We investigate an analytic model to compute nonlinear power spectrum of dark
matter, galaxies and their cross-correlation. The model is based on
Press-Schechter halos, which cluster and have realistic dark matter profiles.
The total power spectrum is a sum of two contributions, one from correlations
betwen the halos and one from correlations within the same halo. We show that
such a model can give dark matter power spectra which match well with the
results of N-body simulations, provided that concentration parameter decreases
with the halo mass.
Galaxy power spectrum differs from dark matter power spectrum because pair
weighted number of galaxies increases less rapidly than the halo mass, as
predicted by theoretical models and observed in clusters. In this case the
resulting power spectrum becomes a power law with the slope closed to the
observed. Such a model also predicts a later onset of nonlinear clustering
compared to the dark matter, which is needed to reconcile the CDM models with
the data. Generic prediction of this model is that bias is scale dependent and
nonmonotonic. For red or elliptical galaxies bias in power spectrum may be
scale dependent even on very large scales.
Our predictions for galaxy-dark matter correlations, which can be observed
through the galaxy-galaxy lensing, show that these cannot be interpreted simply
as an average halo profile of a typical galaxy, because different halo masses
dominate at different scales and because larger halos host more than one
galaxy. We discuss the prospects of using cross-correlations in combination
with galaxy clustering to determine the dark matter power spectrum (ABRIDGED).Comment: 16 pages, 7 figures, submitted to Phys. Rev.
Tomographic Magnification of Lyman Break Galaxies in The Deep Lens Survey
Using about 450,000 galaxies in the Deep Lens Survey, we present a detection
of the gravitational magnification of z > 4 Lyman Break Galaxies by massive
foreground galaxies with 0.4 < z < 1.0, grouped by redshift. The magnification
signal is detected at S/N greater than 20, and rigorous checks confirm that it
is not contaminated by any galaxy sample overlap in redshift. The inferred
galaxy mass profiles are consistent with earlier lensing analyses at lower
redshift. We then explore the tomographic lens magnification signal by
splitting our foreground galaxy sample into 7 redshift bins. Combining
galaxy-magnification cross-correlations and galaxy angular auto-correlations,
we develop a bias-independent estimator of the tomographic signal. As a
diagnostic of magnification tomography, the measurement of this estimator
rejects a flat dark matter dominated Universe at > 7.5{\sigma} with a fixed
\sigma_8 and is found to be consistent with the expected redshift-dependence of
the WMAP7 {\Lambda}CDM cosmology.Comment: 12 pages, 9 figures, Accepted to MNRA
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