1,038 research outputs found
Resource Letter: Gravitational Lensing
This Resource Letter provides a guide to a selection of the literature on
gravitational lensing and its applications. Journal articles, books, popular
articles, and websites are cited for the following topics: foundations of
gravitational lensing, foundations of cosmology, history of gravitational
lensing, strong lensing, weak lensing, and microlensing.Comment: Resource Letter, 2012, in press
(http://ajp.dickinson.edu/Readers/resLetters.html); 21 pages, no figures;
diigo version available at
http://groups.diigo.com/group/gravitational-lensin
The Sloan Lens ACS Survey. IX. Colors, Lensing and Stellar Masses of Early-type Galaxies
We present the current photometric dataset for the Sloan Lens ACS (SLACS)
Survey, including HST photometry from ACS, WFPC2, and NICMOS. These data have
enabled the confirmation of an additional 15 grade `A' (certain) lens systems,
bringing the number of SLACS grade `A' lenses to 85; including 13 grade `B'
(likely) systems, SLACS has identified nearly 100 lenses and lens candidates.
Approximately 80% of the grade `A' systems have elliptical morphologies while
~10% show spiral structure; the remaining lenses have lenticular morphologies.
Spectroscopic redshifts for the lens and source are available for every system,
making SLACS the largest homogeneous dataset of galaxy-scale lenses to date. We
have developed a novel Bayesian stellar population analysis code to determine
robust stellar masses with accurate error estimates. We apply this code to
deep, high-resolution HST imaging and determine stellar masses with typical
statistical errors of 0.1 dex; we find that these stellar masses are unbiased
compared to estimates obtained using SDSS photometry, provided that informative
priors are used. The stellar masses range from 10^10.5 to 10^11.8 M and
the typical stellar mass fraction within the Einstein radius is 0.4, assuming a
Chabrier IMF. The ensemble properties of the SLACS lens galaxies, e.g. stellar
masses and projected ellipticities, appear to be indistinguishable from other
SDSS galaxies with similar stellar velocity dispersions. This further supports
that SLACS lenses are representative of the overall population of massive
early-type galaxies with M* >~ 10^11 M, and are therefore an ideal
dataset to investigate the kpc-scale distribution of luminous and dark matter
in galaxies out to z ~ 0.5.Comment: 20 pages, 18 figures, 5 tables, published in Ap
Strong Lensing by Galaxies
Strong lensing is a powerful tool to address three major astrophysical
issues: understanding the spatial distribution of mass at kpc and sub-kpc
scale, where baryons and dark matter interact to shape galaxies as we see them;
determining the overall geometry, content, and kinematics of the universe;
studying distant galaxies, black holes, and active nuclei that are too small or
too faint to be resolved or detected with current instrumentation. After
summarizing strong gravitational lensing fundamentals, I present a selection of
recent important results. I conclude by discussing the exciting prospects of
strong gravitational lensing in the next decade.Comment: ARA&A Vol 48 in press; preprint version prepared by the author
The mass profile of early-type galaxies in overdense environments: the case of the double source plane gravitational lens SL2SJ02176-0513
SL2SJ02176-0513 is a remarkable lens for the presence of two multiply-imaged
systems at different redshifts lensed by a foreground massive galaxy at : a bright cusp arc at and an additional
double-image system at an estimated redshift of based on
photometry and lensing geometry. The system is located about 400 kpc away from
the center of a massive group of galaxies. Mass estimates for the group are
available from X-ray observations and satellite kinematics. Multicolor
photometry provides an estimate of the stellar mass of the main lens galaxy.
The lensing galaxy is modeled with two components (stars and dark matter), and
we include the perturbing effect of the group environment, and all available
constraints. We find that classic lensing degeneracies, e.g. between external
convergence and mass density slope, are significantly reduced with respect to
standard systems and infer tight constraints on the mass density profile: (i)
the dark matter content of the main lens galaxy is in line with that of typical
galaxies ; (ii) the required mass
associated with the dark matter halo of the nearby group is consistent with
X-ray and weak-lensing estimates (); (iii)
accounting for the group contribution in the form of an external convergence,
the slope of the mass density profile of the main lens galaxy alone is found to
be , consistent with the isothermal ()
slope. We demonstrate that multiple source plane systems together with good
ancillary dataset can be used to disentangle local and environmental effects.Comment: 10 pages, 6 figures, submitted to A&
The Baryon Fractions and Mass-to-Light Ratios of Early-Type Galaxies
We jointly model 22 early-type gravitational lens galaxies with stellar
dynamical measurements using standard CDM halo models. The sample is
inhomogeneous in both its mass distributions and the evolution of its stellar
populations unless the true uncertainties are significantly larger than the
reported measurement errors. In general, the individual systems cannot
constrain halo models, in the sense that the data poorly constrains the stellar
mass fraction of the halo. The ensemble of systems, however, strongly
constrains the average stellar mass represented by the visible galaxies to
of the halo mass if we neglect adiabatic compression, rising to
of the halo mass if we include adiabatic compression. Both
estimates are significantly smaller than the global baryon fraction,
corresponding to a star formation efficiency for early-type galaxies of
. In the adiabatically compressed models, we find an average local
B-band stellar mass-to-light ratio of (M/L)_0 =
(7.2\pm0.5)(M_{\sun}/L_{\sun}) that evolves by
per unit redshift. Adjusting the isotropy of the stellar orbits has little
effect on the results. The adiabatically compressed models are strongly favored
if we impose either local estimates of the mass-to-light ratios of early-type
galaxies or the weak lensing measurements for the lens galaxies on 100 kpc
scales as model constraints.Comment: 9 figure
Separating baryons and dark matter in cluster cores: a full 2-D lensing and dynamic analysis of Abell 383 and MS2137-23
(abridged) We utilize existing imaging and spectroscopic data for the galaxy
clusters MS2137-23 and Abell 383 to present improved measures of the
distribution of dark and baryonic material in the clusters' central regions.
Our method, based on the combination of gravitational lensing and dynamical
data, is uniquely capable of separating the distribution of dark and baryonic
components at scales below 100 kpc. We find a variety of strong lensing models
fit the available data, including some with dark matter profiles as steep as
expected from recent simulations. However, when combined with stellar velocity
dispersion data for the brightest member, shallower inner slopes than predicted
by numerical simulations are preferred. For Abell 383, the preferred shallow
inner slopes are statistically a good fit only when the multiple image position
uncertainties associated with our lens model are assumed to be 0\farcs5, to
account for unknown substructure. No statistically satisfactory fit was
obtained matching both the multiple image lensing data and the velocity
dispersion profile of the brightest cluster galaxy in MS2137-23. This suggests
that the mass model we are using, which comprises a pseudo-elliptical
generalized NFW profile and a brightest cluster galaxy component may
inadequately represent the inner cluster regions. This may plausibly arise due
to halo triaxiality or by the gravitational interaction of baryons and dark
matter in cluster cores. However, the progress made via this detailed study
highlights the key role that complementary observations of lensed features and
stellar dynamics offer in understanding the interaction between dark and
baryonic matter on non-linear scales in the central regions of clusters.Comment: 18 pages, 9 figures; accepted for publication in the Astrophysical
Journa
Keck Spectroscopy of distant GOODS Spheroidal Galaxies: Downsizing in a Hierarchical Universe
We analyze the evolution of the Fundamental Plane for 141 field spheroidal
galaxies in the redshift range 0.2<z<1.2, selected morphologically to a
magnitude limit F850LP=22.43 in the northern field of the Great Observatories
Origin Survey. For massive galaxies we find that the bulk of the star formation
was completed prior to z=2. However, for the lower mass galaxies, the
luminosity-weighted ages are significantly younger. The differential change in
mass-to-light ratio correlates closely with rest-frame color, consistent with
recent star formation and associated growth. Our data are consistent with mass
rather than environment governing the overall growth, contrary to the
expectations of hierarchical assembly. We discuss how feedback, conduction, and
galaxy interactions may explain the downsizing trends seen within our large
sample.Comment: ApJ Letters, in press. 4 figure
The evolution of field early-type galaxies to z~0.7
We have measured the Fundamental Plane (FP) parameters for a sample of 30
field early-type galaxies (E/S0) in the redshift range 0.1<z<0.66. We find
that: i) the FP is defined and tight out to the highest redshift bin; ii) the
intercept \gamma evolves as d\gamma/dz=0.58+0.09-0.13 (for \Omega=0.3,
\Omega_{\Lambda}=0.7), or, in terms of average effective mass to light ratio,
as d\log(M/L_B)/dz=-0.72+0.11-0.16, i.e. faster than is observed for cluster
E/S0 -0.49+-0.05. In addition, we detect [OII] emission >5\AA in 22% of an
enlarged sample of 42 massive E/S0 in the range 0.1<z<0.73, in contrast with
the quiescent population observed in clusters at similar z. We interpret these
findings as evidence that a significant fraction of massive field E/S0
experiences secondary episodes of star-formation at z<1.Comment: ApJ Letters, in pres
Luminous Satellites II: Spatial Distribution, Luminosity Function and Cosmic Evolution
We infer the normalization and the radial and angular distributions of the
number density of satellites of massive galaxies
() between redshifts 0.1 and 0.8 as a function
of host stellar mass, redshift, morphology and satellite luminosity. Exploiting
the depth and resolution of the COSMOS HST images, we detect satellites up to
eight magnitudes fainter than the host galaxies and as close as 0.3 (1.4)
arcseconds (kpc). Describing the number density profile of satellite galaxies
to be a projected power law such that P(R)\propto R^{\rpower}, we find
\rpower=-1.1\pm 0.3. We find no dependency of \rpower on host stellar mass,
redshift, morphology or satellite luminosity. Satellites of early-type hosts
have angular distributions that are more flattened than the host light profile
and are aligned with its major axis. No significant average alignment is
detected for satellites of late-type hosts. The number of satellites within a
fixed magnitude contrast from a host galaxy is dependent on its stellar mass,
with more massive galaxies hosting significantly more satellites. Furthermore,
high-mass late-type hosts have significantly fewer satellites than early-type
galaxies of the same stellar mass, likely a result of environmental
differences. No significant evolution in the number of satellites per host is
detected. The cumulative luminosity function of satellites is qualitatively in
good agreement with that predicted using subhalo abundance matching techniques.
However, there are significant residual discrepancies in the absolute
normalization, suggesting that properties other than the host galaxy luminosity
or stellar mass determine the number of satellites.Comment: 23 pages, 12 figures, Accepted for publication in the Astrophysical
Journa
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