1,572 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
Cosmological constant and time delay
The effect of the cosmological constant on the time delay caused by an
isolated spherical mass is calculated without using the lens equation and
compared to a recent observational bound on the time delay of the lensed quasar
SDSS J1004+4112.Comment: 8 pages, 1 figur
Discovery of Multiply Imaged Galaxies behind the Cluster and Lensed Quasar SDSS J1004+4112
We have identified three multiply imaged galaxies in Hubble Space Telescope
images of the redshift z=0.68 cluster responsible for the large-separation
quadruply lensed quasar, SDSS J1004+4112. Spectroscopic redshifts have been
secured for two of these systems using the Keck I 10m telescope. The most
distant lensed galaxy, at z=3.332, forms at least four images, and an Einstein
ring encompassing 3.1 times more area than the Einstein ring of the lensed QSO
images at z=1.74, due to the greater source distance. For a second multiply
imaged galaxy, we identify Ly_alpha emission at a redshift of z=2.74. The
cluster mass profile can be constrained from near the center of the brightest
cluster galaxy, where we observe both a radial arc and the fifth image of the
lensed quasar, to the Einstein radius of the highest redshift galaxy, ~110 kpc.
Our preliminary modeling indicates that the mass approximates an elliptical
body, with an average projected logarithmic gradient of ~-0.5. The system is
potentially useful for a direct measurement of world models in a previously
untested redshift range.Comment: 5 pages, 3 figures. Accepted by ApJL. High resolution version of the
paper can be found at: http://wise-obs.tau.ac.il/~kerens/papers.htm
Strong lensing in the Einstein-Straus solution
We analyse strong lensing in the Einstein-Straus solution with positive
cosmological constant. For concreteness we compare the theory to the light
deflection of the lensed quasar SDSS J1004+4112.Comment: 14 pages, 3 figures, 5 tables. To the memory of J\"urgen Ehlers v2
contains a note added during publication in GRG and less typo
The Rewards of Patience: An 822 Day Time Delay in the Gravitational Lens SDSS J1004+4112
We present 107 new epochs of optical monitoring data for the four brightest
images of the gravitational lens SDSS J1004+4112 observed between October 2006
and June 2007. Combining this data with the previously obtained light curves,
we determine the time delays between images A, B and C. We confirm our previous
measurement finding that A leads B by dt_BA=40.6+-1.8 days, and find that image
C leads image A by dt_CA=821.6+-2.1 days. The lower limit on the remaining
delay is that image D lags image A by dt_AD>1250 days. Based on the
microlensing of images A and B we estimate that the accretion disk size at a
rest wavelength of 2300 angstrom is 10^{14.8+-0.3} cm for a disk inclination of
cos{i}=1/2, which is consistent with the microlensing disk size-black hole mass
correlation function given our estimate of the black hole mass from the MgII
line width of logM_BH/M_sun=8.44+-0.14. The long delays allow us to fill in the
seasonal gaps and assemble a continuous, densely sampled light curve spanning
5.7 years whose variability implies a structure function with a logarithmic
slope of gamma = 0.35+-0.02. As C is the leading image, sharp features in the C
light curve can be intensively studied 2.3 years later in the A/B pair,
potentially allowing detailed reverberation mapping studies of a quasar at
minimal cost.Comment: Submitted to ApJ, 12 pages, 3 figure
The dual nature of 5f electrons and origin of heavy fermions in U compounds
We develop a theory for the electronic excitations in UPt which is based
on the localization of two of the electrons. The remaining electron is
delocalized and acquires a large effective mass by inducing intra-atomic
excitations of the localized ones. The measured deHaas-vanAlphen frequencies of
the heavy quasiparticles are explained as well as their anisotropic heavy mass.
A model calculation for a small cluster reveals why only the largest of the
different hopping matrix elements is operative causing the electrons in
other orbitals to localize.Comment: 6 pages, 3 figure
The Third Image of the Large-Separation Lensed Quasar SDSS J1029+2623
We identify a third image in the unique quasar lens SDSS J1029+2623, the
second known quasar lens produced by a massive cluster of galaxies. The
spectrum of the third image shows similar emission and absorption features, but
has a redder continuum than the other two images which can be explained by
differential extinction or microlensing. We also identify several lensed arcs.
Our observations suggest a complicated structure of the lens cluster at z~0.6.
We argue that the three lensed images are produced by a naked cusp on the basis
of successful mass models, the distribution of cluster member galaxies, and the
shapes and locations of the lensed arcs. Lensing by a naked cusp is quite rare
among galaxy-scale lenses but is predicted to be common among large-separation
lensed quasars. Thus the discovery can be viewed as support for an important
theoretical prediction of the standard cold dark matter model.Comment: 5 pages, 3 figures, accepted for publication in ApJ Letter
Chandra Observations of SDSS J1004+4112: Constraints on the Lensing Cluster and Anomalous X-Ray Flux Ratios of the Quadruply Imaged Quasar
We present results from Chandra observations of SDSS J1004+4112, a strongly
lensed quasar system with a maximum image separation of 15". All four bright
images of the quasar, as well as resolved X-ray emission originating from the
lensing cluster, are clearly detected. The emission from the lensing cluster
extends out to approximately 1.5 arcmin. We measure the bolometric X-ray
luminosity and temperature of the lensing cluster to be 4.7e44 erg s^-1 and 6.4
keV, consistent with the luminosity-temperature relation for distant clusters.
The mass estimated from the X-ray observation shows excellent agreement with
the mass derived from gravitational lensing. The X-ray flux ratios of the
quasar images differ markedly from the optical flux ratios, and the combined
X-ray spectrum of the images possesses an unusually strong Fe Kalpha emission
line, both of which are indicative of microlensing.Comment: 9 pages, 5 figures. Accepted for publication in ApJ. Version with
high-quality color figures at
http://cosmic.riken.jp/ota/publications/index.htm
Discovery of a Gravitationally Lensed Quasar from the Sloan Digital Sky Survey: SDSS J133222.62+034739.9
We report the discovery of the two-image gravitationally lensed quasar SDSS
J133222.62+034739.9 (SDSS J1332+0347) with an image separation of
Delta_theta=1.14". This system consists of a source quasar at z_s=1.445 and a
lens galaxy at z_l=0.191. The agreement of the luminosity, ellipticity and
position angle of the lens galaxy with those expected from lens model confirms
the lensing hypothesis.Comment: 16 pages, 4 figures, the Astronomical Journal accepte
The Sloan Digital Sky Survey Quasar Lens Search. III. Constraints on Dark Energy from the Third Data Release Quasar Lens Catalog
We present cosmological results from the statistics of lensed quasars in the
Sloan Digital Sky Survey (SDSS) Quasar Lens Search. By taking proper account of
the selection function, we compute the expected number of quasars lensed by
early-type galaxies and their image separation distribution assuming a flat
universe, which is then compared with 7 lenses found in the SDSS Data Release 3
to derive constraints on dark energy under strictly controlled criteria. For a
cosmological constant model (w=-1) we obtain
\Omega_\Lambda=0.74^{+0.11}_{-0.15}(stat.)^{+0.13}_{-0.06}(syst.). Allowing w
to be a free parameter we find
\Omega_M=0.26^{+0.07}_{-0.06}(stat.)^{+0.03}_{-0.05}(syst.) and
w=-1.1\pm0.6(stat.)^{+0.3}_{-0.5}(syst.) when combined with the constraint from
the measurement of baryon acoustic oscillations in the SDSS luminous red galaxy
sample. Our results are in good agreement with earlier lensing constraints
obtained using radio lenses, and provide additional confirmation of the
presence of dark energy consistent with a cosmological constant, derived
independently of type Ia supernovae.Comment: 9 pages, 3 figures, 2 tables, accepted for publication in A
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