760 research outputs found
The SL2S Galaxy-scale Lens Sample. III. Lens Models, Surface Photometry and Stellar Masses for the final sample
We present Hubble Space Telescope (HST) imaging data and CFHT Near IR
ground-based images for the final sample of 56 candidate galaxy-scale lenses
uncovered in the CFHT Legacy Survey as part of the Strong Lensing in the Legacy
Survey (SL2S) project. The new images are used to perform lens modeling,
measure surface photometry, and estimate stellar masses of the deflector
early-type galaxies. Lens modeling is performed on the HST images (or CFHT when
HST is not available) by fitting the spatially extended light distribution of
the lensed features assuming a singular isothermal ellipsoid mass profile and
by reconstructing the intrinsic source light distribution on a pixelized grid.
Based on the analysis of systematic uncertainties and comparison with inference
based on different methods we estimate that our Einstein Radii are accurate to
\sim3%. HST imaging provides a much higher success rate in confirming
gravitational lenses and measuring their Einstein radii than CFHT imaging does.
Lens modeling with ground-based images however, when successful, yields
Einstein radius measurements that are competitive with spaced-based images.
Information from the lens models is used together with spectroscopic
information from the companion paper IV to classify the systems, resulting in a
final sample of 39 confirmed (grade-A) lenses and 17 promising candidates. The
redshifts of the main deflector span a range 0.3<zd< 0.8, providing an
excellent sample for the study of the cosmic evolution of the mass distribution
of early-type galaxies over the second half of the history of the Universe.Comment: Submitted to The Astrophysical Journa
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 SL2S Galaxy-scale Lens Sample. V. Dark Matter Halos and Stellar IMF of Massive Early-type Galaxies out to Redshift 0.8
We investigate the cosmic evolution of the internal structure of massive
early-type galaxies over half of the age of the Universe. We perform a joint
lensing and stellar dynamics analysis of a sample of 81 strong lenses from the
SL2S and SLACS surveys and combine the results with a hierarchical Bayesian
inference method to measure the distribution of dark matter mass and stellar
IMF across the population of massive early-type galaxies. Lensing selection
effects are taken into account. We find that the dark matter mass projected
within the inner 5 kpc increases for increasing redshift, decreases for
increasing stellar mass density, but is roughly constant along the evolutionary
tracks of early-type galaxies. The average dark matter slope is consistent with
that of an NFW profile, but is not well constrained. The stellar IMF
normalization is close to a Salpeter IMF at and scales
strongly with increasing stellar mass. No dependence of the IMF on redshift or
stellar mass density is detected. The anti-correlation between dark matter mass
and stellar mass density supports the idea of mergers being more frequent in
more massive dark matter halos.Comment: Accepted for publication on The Astrophysical Journal. Revised
version. (25 pages, 18 figures
The SL2S Galaxy-scale Lens Sample. IV. The dependence of the total mass density profile of early-type galaxies on redshift, stellar mass, and size
We present optical and near infrared spectroscopy obtained at Keck, VLT, and
Gemini for a sample of 36 secure strong gravitational lens systems and 17
candidates identified as part of the SL2S survey. The deflectors are massive
early-type galaxies in the redshift range z_d=0.2-0.8, while the lensed sources
are at z_s=1-3.5. We combine this data with photometric and lensing
measurements presented in the companion paper III and with lenses from the
SLACS and LSD surveys to investigate the cosmic evolution of the internal
structure of massive early-type galaxies over half the age of the universe. We
study the dependence of the slope of the total mass density profile \gamma'
(\rho(r)\propto r^{-\gamma'}) on stellar mass, size, and redshift. We find that
two parameters are sufficent to determine \gamma' with less than 6% residual
scatter. At fixed redshift, \gamma' depends solely on the surface stellar mass
density \partial \gamma'/ \partial \Sigma_*=0.38\pm 0.07, i.e. galaxies with
denser stars also have steeper slopes. At fixed M_* and R_{eff}, \gamma'
depends on redshift, in the sense that galaxies at a lower redshift have
steeper slopes (\partial \gamma' / \partial z = -0.31\pm 0.10). However, the
mean redshift evolution of \gamma' for an individual galaxy is consistent with
zero d\gamma'/dz=-0.10\pm0.12. This result is obtained by combining our
measured dependencies of \gamma' on z,M_*,R_{eff} with the evolution of the
R_{eff}-M_* taken from the literature, and is broadly consistent with current
models of the formation and evolution of massive early-type galaxies. Detailed
quantitative comparisons of our results with theory will provide qualitatively
new information on the detailed physical processes at work.Comment: Submitted to The Astrophysical Journa
Too Much SALT? The Nuanced Impact of the State and Local Tax Deduction Cap on Pass-Through Business Taxpayers
Perhaps the most controversial provision of the Tax Cuts and Jobs Act of 2017 is the state and local tax deduction limitation (or SALT cap), partic¬ularly with respect to how the cap impacts pass-through entities in high-tax states. This particular provision of the tax law has been criticized by opponents as deliberately punitive to small businesses in blue states, while proponents maintain that eliminating the SALT cap would primar¬ily benefit high income taxpayers. Politicians from blue states have called for the repeal of the SALT cap, and some states have enacted various workarounds with questionable prospects of success. Still, many taxpay¬ers will not benefit from a SALT deduction irrespective of the SALT cap, particularly taxpayers that either take the standard deduction or are subject to the alternative minimum tax (AMT). We examine the developing law around the SALT cap and provide descriptive empirical evidence of its disparate impact on closely held business taxpayers. Consistent with prior economics literature, we find that the impact is indeed most pro¬nounced among high-income taxpayers in blue states. However, we note that the impact is substantially less than the furor over the limitation would suggest because many high-income taxpayers are subject to the AMT and so are not significantly affected by the limitation. These findings suggest two underemphasized points. First, the imposition of the SALT cap was not the drastic financial hit to blue state taxpayers that policy makers and commentators have suggested. Second, with a new adminis¬tration that favors eliminating the SALT cap, Congress could consider whether the repeal of the cap alone is enough because further changes would be needed to return the SALT deduction to its earlier prominence
Testing the Evolution of the Correlations between Supermassive Black Holes and their Host Galaxies using Eight Strongly Lensed Quasars
One of the main challenges in using high redshift active galactic nuclei to
study the correlations between the mass of the supermassive Black Hole (MBH)
and the properties of their active host galaxies is instrumental resolution.
Strong lensing magnification effectively increases instrumental resolution and
thus helps to address this challenge. In this work, we study eight strongly
lensed active galactic nuclei (AGN) with deep Hubble Space Telescope imaging,
using the lens modelling code Lenstronomy to reconstruct the image of the
source. Using the reconstructed brightness of the host galaxy, we infer the
host galaxy stellar mass based on stellar population models. MBH are estimated
from broad emission lines using standard methods. Our results are in good
agreement with recent work based on non-lensed AGN, demonstrating the potential
of using strongly lensed AGNs to extend the study of the correlations to higher
redshifts. At the moment, the sample size of lensed AGN is small and thus they
provide mostly a consistency check on systematic errors related to resolution
for the non-lensed AGN. However, the number of known lensed AGN is expected to
increase dramatically in the next few years, through dedicated searches in
ground and space based wide field surveys, and they may become a key diagnostic
of black hole and galaxy co-evolution.Comment: 12 pages, 4 figures, 3 tables. MNRAS in press. Comments welcom
Probing dark matter substructure in the gravitational lens HE0435-1223 with the WFC3 grism
Strong gravitational lensing provides a powerful test of Cold Dark Matter
(CDM) as it enables the detection and mass measurement of low mass haloes even
if they do not contain baryons. Compact lensed sources such as Active Galactic
Nuclei (AGN) are particularly sensitive to perturbing subhalos, but their use
as a test of CDM has been limited by the small number of systems which have
significant radio emission which is extended enough avoid significant lensing
by stars in the plane of the lens galaxy, and red enough to be minimally
affected by differential dust extinction. Narrow-line emission is a promising
alternative as it is also extended and, unlike radio, detectable in virtually
all optically selected AGN lenses. We present first results from a WFC3 grism
narrow-line survey of lensed quasars, for the quadruply lensed AGN HE0435-1223.
Using a forward modelling pipeline which enables us to robustly account for
spatial blending, we measure the [OIII] 5007 \AA~ flux ratios of the four
images. We find that the [OIII] fluxes and positions are well fit by a simple
smooth mass model for the main lens. Our data rule out a NFW perturber projected within 1\farcs0 (0\farcs1)
arcseconds of each of the lensed images, where is the perturber mass
within its central 600 pc. The non-detection is broadly consistent with the
expectations of CDM for a single system. The sensitivity achieved
demonstrates that powerful limits on the nature of dark matter can be obtained
with the analysis of narrow-line lenses.Comment: Accepted for publication in MNRAS, 15 pages, 8 figure
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