738 research outputs found
ULAS J234311.93-005034.0: A gravitational lens system selected from UKIDSS and SDSS
We report the discovery of a new gravitational lens system. This object, ULAS
J234311.93-005034.0, is the first to be selected by using the new UKIRT
Infrared Deep Sky Survey (UKIDSS), together with the Sloan Digital Sky Survey
(SDSS). The ULAS J234311.93-005034.0 system contains a quasar at redshift 0.788
which is doubly imaged, with separation 1.4". The two quasar images have the
same redshift and similar, though not identical, spectra. The lensing galaxy is
detected by subtracting point-spread functions from R-band images taken with
the Keck telescope. The lensing galaxy can also be detected by subtracting the
spectra of the A and B images, since more of the galaxy light is likely to be
present in the latter. No redshift is determined from the galaxy, although the
shape of its spectrum suggests a redshift of about 0.3. The object's lens
status is secure, due to the identification of two objects with the same
redshift together with a lensing galaxy. Our imaging suggests that the lens is
found in a cluster environment, in which candidate arc-like structures, that
require confirmation, are visible in the vicinity. Further discoveries of
lenses from the UKIDSS survey are likely as part of this programme, due to the
depth of UKIDSS and its generally good seeing conditions.Comment: Accepted by MNRA
Combining cluster observables and stacked weak lensing to probe dark energy: Self-calibration of systematic uncertainties
We develop a new method of combining cluster observables (number counts and
cluster-cluster correlation functions) and stacked weak lensing signals of
background galaxy shapes, both of which are available in a wide-field optical
imaging survey. Assuming that the clusters have secure redshift estimates, we
show that the joint experiment enables a self-calibration of important
systematic errors including the source redshift uncertainty and the cluster
mass-observable relation, by adopting a single population of background source
galaxies for the lensing analysis. It allows us to use the relative strengths
of stacked lensing signals at different cluster redshifts for calibrating the
source redshift uncertainty, which in turn leads to accurate measurements of
the mean cluster mass in each bin. In addition, our formulation of stacked
lensing signals in Fourier space simplifies the Fisher matrix calculations, as
well as the marginalization over the cluster off-centering effect, the most
significant uncertainty in stacked lensing. We show that upcoming wide-field
surveys yield stringent constraints on cosmological parameters including dark
energy parameters, without any priors on nuisance parameters that model
systematic uncertainties. Specifically, the stacked lensing information
improves the dark energy FoM by a factor of 4, compared to that from the
cluster observables alone. The primordial non-Gaussianity parameter can also be
constrained with a level of f_NL~10. In this method, the mean source redshift
is well calibrated to an accuracy of 0.1 in redshift, and the mean cluster mass
in each bin to 5-10% accuracies, which demonstrates the success of the
self-calibration of systematic uncertainties from the joint experiment.
(Abridged)Comment: 29 pages, 17 figures, 6 tables, accepted for publication in Phys.
Rev.
The BOSS Emission-Line Lens Survey. III. : Strong Lensing of Ly Emitters by Individual Galaxies
We introduce the Baryon Oscillation Spectroscopic Survey (BOSS) Emission-Line
Lens Survey (BELLS) for GALaxy-Ly EmitteR sYstems (BELLS GALLERY)
Survey, which is a Hubble Space Telescope program to image a sample of
galaxy-scale strong gravitational lens candidate systems with high-redshift
Ly emitters (LAEs) as the background sources. The goal of the BELLS
GALLERY Survey is to illuminate dark substructures in galaxy-scale halos by
exploiting the small-scale clumpiness of rest-frame far-UV emission in lensed
LAEs, and to thereby constrain the slope and normalization of the
substructure-mass function. In this paper, we describe in detail the
spectroscopic strong-lens selection technique, which is based on methods
adopted in the previous Sloan Lens ACS (SLACS) Survey, BELLS, and SLACS for the
Masses Survey. We present the BELLS GALLERY sample of the 21 highest-quality
galaxy--LAE candidates selected from galaxy spectra
in the BOSS of the Sloan Digital Sky Survey III. These systems consist of
massive galaxies at redshifts of approximately 0.5 strongly lensing LAEs at
redshifts from 2--3. The compact nature of LAEs makes them an ideal probe of
dark substructures, with a substructure-mass sensitivity that is unprecedented
in other optical strong-lens samples. The magnification effect from lensing
will also reveal the structure of LAEs below 100 pc scales, providing a
detailed look at the sites of the most concentrated unobscured star formation
in the universe. The source code used for candidate selection is available for
download as a part of this release.Comment: 14 pages, 5 figures, accepted for publication in the ApJ (ApJ, 824,
86). Minor edits to match the ApJ published versio
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