1,903 research outputs found
SDSS J131339.98+515128.3: A new gravitationally lensed quasar selected based on near-infrared excess
We report the discovery of a new gravitationally lensed quasar, SDSS
J131339.98+515128.3, at a redshift of 1.875 with an image separation of 1.24".
The lensing galaxy is clearly detected in visible-light follow-up observations.
We also identify three absorption-line doublets in the spectra of the lensed
quasar images, from which we measure the lens redshift to be 0.194. Like
several other known lenses, the lensed quasar images have different continuum
slopes. This difference is probably the result of reddening and microlensing in
the lensing galaxy. The lensed quasar was selected by correlating Sloan Digital
Sky Survey (SDSS) spectroscopic quasars with Two Micron All Sky Survey (2MASS)
sources and choosing quasars that show near-infrared (IR) excess. The near-IR
excess can originate, for example, from the contribution of the lensing galaxy
at near-IR wavelengths. We show that the near-IR excess technique is indeed an
efficient method to identify lensed systems from a large sample of quasars.Comment: Accepted to MNRAS, 8 pages, 7 figure
A Two-Year Time Delay for the Lensed Quasar SDSS J1029+2623
We present 279 epochs of optical monitoring data spanning 5.4 years from 2007
January to 2012 June for the largest image separation (22.6 arcsec)
gravitationally lensed quasar, SDSS J1029+2623. We find that image A leads the
images B and C by dt_AB = (744+-10) days (90% confidence); the uncertainty
includes both statistical uncertainties and systematic differences due to the
choice of models. With only a ~1% fractional error, the interpretation of the
delay is limited primarily by cosmic variance due to fluctuations in the mean
line-of-sight density. We cannot separate the fainter image C from image B, but
since image C trails image B by only 2-3 days in all models, the estimate of
the time delay between image A and B is little affected by combining the fluxes
of images B and C. There is weak evidence for a low level of microlensing,
perhaps created by the small galaxy responsible for the flux ratio anomaly in
this system. Interpreting the delay depends on better constraining the shape of
the gravitational potential using the lensed host galaxy, other lensed arcs and
the structure of the X-ray emission.Comment: Accepted for publication in The Astrophysical Journal. Changes in
response to referee's comment
The Kondo crossover in shot noise of a single quantum dot with orbital degeneracy
We investigate out of equilibrium transport through an orbital Kondo system
realized in a single quantum dot, described by the multiorbital impurity
Anderson model. Shot noise and current are calculated up to the third order in
bias voltage in the particle-hole symmetric case, using the renormalized
perturbation theory. The derived expressions are asymptotically exact at low
energies. The resulting Fano factor of the backscattering current is
expressed in terms of the Wilson ratio and the orbital degeneracy as
at zero temperature. Then,
for small Coulomb repulsions , we calculate the Fano factor exactly up to
terms of order , and also carry out the numerical renormalization group
calculation for intermediate in the case of two- and four-fold degeneracy
(). As increases, the charge fluctuation in the dot is suppressed,
and the Fano factor varies rapidly from the noninteracting value to the
value in the Kondo limit , near the crossover region
, with the energy scale of the hybridization .Comment: 10 pages, 4 figure
The quasar-galaxy cross SDSS J1320+1644: A probable large-separation lensed quasar
We report the discovery of a pair of quasars at , with a separation
of 8\farcs585\pm0\farcs002. Subaru Telescope infrared imaging reveals the
presence of an elliptical and a disk-like galaxy located almost symmetrically
between the quasars, creating a cross-like configuration. Based on absorption
lines in the quasar spectra and the colors of the galaxies, we estimate that
both galaxies are located at redshift . This, as well as the
similarity of the quasar spectra, suggests that the system is a single quasar
multiply imaged by a galaxy group or cluster acting as a gravitational lens,
although the possibility of a binary quasar cannot be fully excluded. We show
that the gravitational lensing hypothesis implies these galaxies are not
isolated, but must be embedded in a dark matter halo of virial mass assuming an NFW model with a
concentration parameter of , or a singular isothermal sphere profile
with a velocity dispersion of km s. We place constraints on
the location of the dark matter halo, as well as the velocity dispersions of
the galaxies. In addition, we discuss the influence of differential reddening,
microlensing and intrinsic variability on the quasar spectra and broadband
photometry.Comment: Published in The Astrophysical Journa
Adaptive optics observations of the gravitationally lensed quasar SDSS J1405+0959
We present the result of Subaru Telescope multi-band adaptive optics
observations of the complex gravitationally lensed quasar SDSS J1405+0959,
which is produced by two lensing galaxies. These observations reveal
dramatically enhanced morphological detail, leading to the discovery of an
additional object 0. 26'' from the secondary lensing galaxy, as well as three
collinear clumps located in between the two lensing galaxies. The new object is
likely to be the third quasar image, although the possibility that it is a
galaxy cannot be entirely excluded. If confirmed via future observations, it
would be the first three image lensed quasar produced by two galaxy lenses. In
either case, we show based on gravitational lensing models and photometric
redshift that the collinear clumps represent merging images of a portion of the
quasar host galaxy, with a magnification factor of 15 - 20, depending on the
model.Comment: 12 pages, 8 figures, 7 tables. Submitted to MNRA
Effects of galaxy-halo alignment and adiabatic contraction on gravitational lens statistics
We study the strong gravitational lens statistics of triaxial cold dark
matter (CDM) halos occupied by central early-type galaxies. We calculate the
image separation distribution for double, cusp and quad configurations. The
ratios of image multiplicities at large separations are consistent with the
triaxial NFW model, and at small separations are consistent with the singular
isothermal ellipsoid (SIE) model. At all separations, the total lensing
probability is enhanced by adiabatic contraction. If no adiabatic contraction
is assumed, naked cusp configurations become dominant at approximately 2.5'',
which is inconsistent with the data. We also show that at small-to-moderate
separations, the image multiplicities depend sensitively on the alignment of
the shapes of the luminous and dark matter projected density profiles. In
constrast to other properties that affect these ratios, the degree of alignment
does not have a significant effect on the total lensing probability. These
correlations may therefore be constrained by comparing the theoretical image
separation distribution to a sufficiently large lens sample from future wide
and deep sky surveys such as Pan-Starrs, LSST and JDEM. Understanding the
correlations in the shapes of galaxies and their dark matter halo is important
for future weak lensing surveys.Comment: 10 pages, 7 figure
The Sloan Digital Sky Survey Quasar Lens Search. VI. Constraints on Dark Energy and the Evolution of Massive Galaxies
We present a statistical analysis of the final lens sample from the Sloan
Digital Sky Survey Quasar Lens Search (SQLS). The number distribution of a
complete subsample of 19 lensed quasars selected from 50,836 source quasars is
compared with theoretical expectations, with particular attention to the
selection function. Assuming that the velocity function of galaxies does not
evolve with redshift, the SQLS sample constrains the cosmological constant to
\Omega_\Lambda=0.79^{+0.06}_{-0.07}(stat.)^{+0.06}_{-0.06}(syst.) for a flat
universe. The dark energy equation of state is found to be consistent with w=-1
when the SQLS is combined with constraints from baryon acoustic oscillation
(BAO) measurements or results from the Wilkinson Microwave Anisotropy Probe
(WMAP). We also obtain simultaneous constraints on cosmological parameters and
redshift evolution of the galaxy velocity function, finding no evidence for
redshift evolution at z<1 in any combinations of constraints. For instance,
number density evolution quantified as \nu_n=d\ln\phi_*/d\ln(1+z) and the
velocity dispersion evolution \nu_\sigma=d\ln\sigma_*/d\ln(1+z) are constrained
to \nu_n=1.06^{+1.36}_{-1.39}(stat.)^{+0.33}_{-0.64}(syst.) and
\nu_\sigma=-0.05^{+0.19}_{-0.16}(stat.)^{+0.03}_{-0.03}(syst.) respectively
when the SQLS result is combined with BAO and WMAP for flat models with a
cosmological constant. We find that a significant amount of dark energy is
preferred even after fully marginalizing over the galaxy evolution parameters.
Thus the statistics of lensed quasars robustly confirm the accelerated cosmic
expansion.Comment: 44 pages, 12 figures, 4 tables, accepted for publication in A
The Sloan Digital Sky Survey Quasar Lens Search. V. Final Catalog from the Seventh Data Release
We present the final statistical sample of lensed quasars from the Sloan
Digital Sky Survey (SDSS) Quasar Lens Search (SQLS). The well-defined
statistical lens sample consists of 26 lensed quasars brighter than i=19.1 and
in the redshift range of 0.6<z<2.2 selected from 50,836 spectroscopically
confirmed quasars in the SDSS Data Release 7 (DR7), where we restrict the image
separation range to 1"<\theta<20" and the i-band magnitude differences in two
image lenses to be smaller than 1.25 mag. The SDSS DR7 quasar catalog also
contains 36 additional lenses identified with various techniques. In addition
to these lensed quasars, we have identified 81 pairs of quasars from follow-up
spectroscopy, 26 of which are physically associated binary quasars. The
statistical lens sample covers a wide range of image separations, redshifts,
and magnitudes, and therefore is suitable for systematic studies of
cosmological parameters and surveys of the structure and evolution of galaxies
and quasars.Comment: 42 pages, 2 figures, 6 tables, accepted for publication in AJ; see
http://www-utap.phys.s.u-tokyo.ac.jp/~sdss/sqls/ for supplemental informatio
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