596 research outputs found
A Correlation between Galaxy Light Concentration and Supermassive Black Hole Mass
We present evidence for a strong correlation between the concentration of
bulges and the mass of their central supermassive black hole (M_bh) -- more
concentrated bulges have more massive black holes. Using C_{r_e}(1/3) from
Trujillo, Graham & Caon (2001b) as a measure of bulge concentration, we find
that log (M_bh/M_sun) = 6.81(+/-0.95)C_{r_e}(1/3) + 5.03(+/-0.41). This
correlation is shown to be marginally stronger (Spearman's r_s=0.91) than the
relationship between the logarithm of the stellar velocity dispersion and log
M_bh (Spearman's r_s=0.86), and has comparable, or less, scatter (0.31 dex in
log M_bh), which decreases to 0.19 dex when we use only those galaxies whose
supermassive black hole's radius of influence is resolved and remove one well
understood outlying data point).Comment: 7 pages, 1 table, 2 figures. ApJ Letters, accepte
A photometric method to determine supermassive black hole masses
We report the discovery of a strong correlation between the shape of a
bulge's light-profile and the mass of its central supermassive black hole
(M_{bh}). We find that log(M_{bh}/M_{sun}) = 2.91(+/-0.38)log(n) +
6.37(+/-0.21), where `n' is the Sersic r^{1/n} shape index of the bulge. This
correlation is marginally stronger than the relationship between the logarithm
of the stellar velocity dispersion and log(M_{bh}) and has comparable scatter.
It therefore offers a cheap (in terms of telescope time) alternative to
estimating the masses of supermassive black holes.Comment: 2 pages, Conference presentation: Galaxy Evolution, Theory &
Observation
Photometric scaling relations of lenticular and spiral galaxies
Photometric scaling relations are studied for S0 galaxies and compared with
those for spirals. New 2D K_s-band multi-component decompositions are presented
for 122 early-type disk galaxies. Combining with our previous decompositions,
the final sample consists of 175 galaxies. As a comparison sample we use the
Ohio State University Bright Spiral Galaxy Survey (OSUBSGS), for which similar
decompositions have previously been made by us. Our main results are: (1)
Important scaling relations are present, indicating that the formative
processes of bulges and disks in S0s are coupled like has been previously found
for spirals. (2) We obtain median r_{eff}/h_r = 0.20, 0.15 and 0.10 for S0,
S0/a-Sa and Sab-Sc galaxies: these are smaller than predicted by simulation
models in which bulges are formed by galaxy mergers. (3) The properties of
bulges of S0s are different from the elliptical galaxies, which is manifested
in the M_K(bulge) vs r_{eff} relation, in the photometric plane, and to some
extent also in the Kormendy relation. The bulges of S0s are similar to bulges
of spirals with M_K(bulge) < -20 mag. Some S0s have small bulges, but their
properties are not compatible with the idea that they could evolve to dwarfs by
galaxy harassment. (4) The relative bulge flux B/T for S0s covers the full
range found in the Hubble sequence. (5) The values and relations of the
parameters of the disks of the S0 galaxies in NIRS0S are similar to those
obtained for spirals in the OSUBSGS. Overall, our results support the view that
spiral galaxies with bulges brighter than -20 mag in the K-band can evolve
directly into S0s, due to stripping of gas followed by truncated star
formation.Comment: Accepted to MNRAS, includes a big figure in electronic form, not
included her
The Black Hole Mass-Bulge Luminosity Relationship for Active Galactic Nuclei from Reverberation Mapping and Hubble Space Telescope Imaging
We investigate the relationship between black hole mass and bulge luminosity
for AGNs with reverberation-based black hole mass measurements and bulge
luminosities from two-dimensional decompositions of Hubble Space Telescope host
galaxy images. We find that the slope of the relationship for AGNs is 0.76-0.85
with an uncertainty of ~0.1, somewhat shallower than the M_BH \propto
L^{1.0+/-0.1} relationship that has been fit to nearby quiescent galaxies with
dynamical black hole mass measurements. This is somewhat perplexing, as the AGN
black hole masses include an overall scaling factor that brings the AGN
M_BH-sigma relationship into agreement with that of quiescent galaxies. We
discuss biases that may be inherent to the AGN and quiescent galaxy samples and
could cause the apparent inconsistency in the forms of their M_BH-L_bulge
relationships.Comment: 5 pages, 3 figures and 2 tables, submitted to ApJ Letter
The near-IR - L and - n relations
We present near-IR surface photometry (2D-profiling) for a sample of 29
nearby galaxies for which super-massive black hole (SMBH) masses are
constrained. The data is derived from the UKIDSS-LASS survey representing a
significant improvement in image quality and depth over previous studies based
on 2MASS data. We derive the spheroid luminosity and spheroid S\'ersic index
for each galaxy with GALFIT3 and use these data to construct SMBH mass -bulge
luminosity (--) and SMBH - S\'ersic index (--)
relations. The best fit K-band relation for elliptical and disk galaxies is
with an intrinsic scatter of 0.4dex whilst for elliptical
galaxies we find with an intrinsic scatter of 0.31dex. Our
revised -- relation agrees closely with the previous near-IR
constraint by \citet{tex:G07}. The lack of improvement in the intrinsic scatter
in moving to higher quality near-IR data suggests that the SMBH relations are
not currently limited by the quality of the imaging data but is either
intrinsic or a result of uncertainty in the precise number of required
components required in the profiling process. Contrary to expectation (see
\citealt{tex:GD07a}) a relation between SMBH mass and the S\'ersic index was
not found at near-IR wavelengths. This latter outcome is believed to be
explained by the generic inconsistencies between 1D and 2D galaxy profiling
which are currently under further investigation.Comment: 35 pages, 37 figures, MNRAS accepte
The stellar mass distribution in early-type disk galaxies: surface photometry and bulge-disk decompositions
We present deep B- and R-band surface photometry for a sample of 21 galaxies
with morphological types between S0 and Sab. We present radial profiles of
surface brightness, colour, ellipticity, position angle and deviations of
axisymmetry for all galaxies, as well as isophotal and effective radii and
total magnitudes. We have decomposed the images into contributions from a
spheroidal bulge and a flat disk, using an interactive, 2D decomposition
technique.
We study in detail the relations between various bulge and disk parameters.
In particular, we find that the bulges of our galaxies have surface brightness
profiles ranging from exponential to De Vaucouleurs, with the average value of
the Sersic shape parameter n being 2.5. In agreement with previous studies, we
find that the shape of the bulge intensity distribution depends on luminosity,
with the more luminous bulges having more centrally peaked light profiles. By
comparing the ellipticity of the isophotes in the bulges to those in the outer,
disk dominated regions, we are able to derive the intrinsic axis ratio q_b of
the bulges. The average axis ratio is 0.55, with an rms spread of 0.12. None of
the bulges in our sample is spherical, whereas in some cases, the bulges can be
as flat as q_b = 0.3 - 0.4. The bulge flattening seems to be weakly coupled to
luminosity, more luminous bulges being on average slightly more flattened than
their lower-luminosity counterparts. Our finding that most bulges are
significantly flattened and have an intensity profile shallower than R^{1/4}
suggests that `pseudobulges', formed from disk material by secular processes,
do not only occur in late-type spiral galaxies, but are a common feature in
early-type disk galaxies as well. (abridged)Comment: 26 pages, 11 figures. Accepted for publication in MNRAS. A
pdf-version with full resolution figures and the full atlas can be found at
http://www.nottingham.ac.uk/~ppzen/surfphot.accepted.pd
A New Empirical Model for the Structural Analysis of Early-type Galaxies and a Critical Review of the Nuker Model
The Nuker law was designed to match the inner few (~3-10) arcseconds of
predominantly nearby (< 30 Mpc) early-type galaxy light-profiles; it was never
intended to describe an entire profile. The Sersic model, on the other hand,
was developed to fit the entire profile; however, due to the presence of
partially depleted galaxy cores, the Sersic model cannot always describe the
very inner region. We have therefore developed a new empirical model consisting
of an inner power-law, a transition region, and an outer Sersic model to
connect the inner and outer structure of elliptical galaxies. Moreover, the
stability of the Nuker model parameters are investigated. Surprisingly, none
are found to be stable quantities; all are shown to vary systematically with a
profile's fitted radial extent, and often by more than 100%. Considering
elliptical galaxies spanning a range of 7.5 magnitudes, the central stellar
density of the underlying host galaxy is observed to increase with galaxy
luminosity until the onset of core formation, detected only in the brightest
elliptical galaxies. We suggest that the so-called ``power-law'' galaxies may
actually be described by the Sersic model over their entire radial range
The nature of late-type spiral galaxies: structural parameters, optical and near-infrared colour profiles, and dust extinction
We analyse V and H-band surface photometry of a sample of 18 Sb-Sd galaxies.
Combining high resolution HST images with ground-based NIR observations, we
extract photometric profiles, which cover the whole disk and provide the
highest possible resolution. This is the first photometric study of late-type
spirals for which the stellar kinematics have been measured. For 10 out of the
18 galaxies, HST data in both F160W (H) and F606W (V) are available, and, for
those, we present colour maps and radial colour profiles at the resolution of
the Hubble Space Telescope.
Colours vary significantly from galaxy to galaxy, but tend to be highly
homogeneous within each galaxy, with smooth and flat colour profiles. Some of
the colour maps show jumps in the inner regions, likely due to dust. We
determine extinction-maps in an almost model-independent way using the V-H
colour map and the SAURON Mg b absorption line map of Ganda et al. (2007). The
maps show that A_V ranges from 0 to 2 mag, in the center from 0 to 1.5 mag, in
agreement with the models of Tuffs et al. (2004).
We describe the surface brightness profiles as the superposition of an
exponential disk and a Sersic bulge. The bulges are small (0.1-2.5 kpc), and
show a shape parameter n ranging from ~ 0.7 to 3, with a mean value smaller
than two: well below the value for the 'classical' de Vaucouleurs bulges. Most
galaxies (16 out of 18) show a central light excess above the Sersic fit to the
bulge, which can be interpreted as a nuclear cluster, as shown by previous
studies. We provide zero-order estimates for the magnitude of these components.
We discuss the correlations among the structural galaxy parameters and with
other relevant quantities (abridged).Comment: 28 pages, 12 figures and 7 tables. Accepted for publication in MNRAS.
Higher resolution version available at
http://www.astro.rug.nl/~peletier/ganda2009.pd
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