5,519 research outputs found
Results from the CASTLES Survey of Gravitational Lenses
We show that most gravitational lenses lie on the passively evolving
fundamental plane for early-type galaxies. For burst star formation models (1
Gyr of star formation, then quiescence) in low Omega_0 cosmologies, the stellar
populations of the lens galaxies must have formed at z_f > 2. Typical lens
galaxies contain modest amounts of patchy extinction, with a median
differential extinction for the optical (radio) selected lenses of E(B-V) =
0.04 (0.07) mag. The dust can be used to determine both extinction laws and
lens redshifts. For example, the z_l=0.96 elliptical lens in MG0414+0534 has an
R_V=1.7 +/- 0.1 mean extinction law. Arc and ring images of the quasar and AGN
source host galaxies are commonly seen in NICMOS H band observations. The hosts
are typically blue, L < L_* galaxies.Comment: 12 pages, 10 figures, from Proceedings of the 9th Annual Astrophysics
Conference in Maryland, After the Dark Ages: When Galaxies Were Youn
Finding Gravitational Lenses With X-rays
There are , 0.1 and 0.01 gravitationally lensed X-ray sources per
square degree with soft X-ray fluxes exceeding and
respectively. These sources will be detected
serendipitously with the Chandra X-ray Observatory at a rate of 1--3 lenses per
year of high resolution imaging. The low detection rate is due to the small
area over which the HRC and ACIS cameras have the <1\farcs5 FWHM resolution
necessary to find gravitational lenses produced by galaxies. Deep images of
rich clusters at intermediate redshifts should yield one wide separation
(\Delta\theta \gtorder 5\farcs0) multiply-imaged background X-ray source for
every , 30 and 300 clusters imaged to the same flux limits.Comment: 13 pages, including 5 figures, submitted to ApJ Letter
Microlensing of the Lensed Quasar SDSS0924+0219
We analyze V, I and H band HST images and two seasons of R-band monitoring
data for the gravitationally lensed quasar SDSS0924+0219. We clearly see that
image D is a point-source image of the quasar at the center of its host galaxy.
We can easily track the host galaxy of the quasar close to image D because
microlensing has provided a natural coronograph that suppresses the flux of the
quasar image by roughly an order of magnitude. We observe low amplitude,
uncorrelated variability between the four quasar images due to microlensing,
but no correlated variations that could be used to measure a time delay. Monte
Carlo models of the microlensing variability provide estimates of the mean
stellar mass in the lens galaxy (0.02 Msun < M < 1.0 Msun), the accretion disk
size (the disk temperature is 5 x 10^4 K at 3.0 x 10^14 cm < rs < 1.4 x 10^15
cm), and the black hole mass (2.0 x 10^7 Msun < MBH \eta_{0.1}^{-1/2}
(L/LE)^{1/2} < 3.3 x 10^8 Msun), all at 68% confidence. The black hole mass
estimate based on microlensing is consistent with an estimate of MBH = 7.3 +-
2.4 x 10^7 Msun from the MgII emission line width. If we extrapolate the
best-fitting light curve models into the future, we expect the the flux of
images A and B to remain relatively stable and images C and D to brighten. In
particular, we estimate that image D has a roughly 12% probability of
brightening by a factor of two during the next year and a 45% probability of
brightening by an order of magnitude over the next decade.Comment: v.2 incorporates referee's comments and corrects two errors in the
original manuscript. 28 pages, 10 figures, published in Ap
Mid-IR Observations and a Revised Time Delay for the Gravitational Lens System Quasar HE 1104-1805
The mid-IR flux ratios F_A/F_B = 2.84 +/- 0.06 of the two images of the
gravitationally lensed quasar HE 1104-1805 show no wavelength dependence to
within 3% across 3.6-8.0 um, no time dependence over 6 months and agree with
the broad emission line flux ratios. This indicates that the mid-IR emission
likely comes from scales large enough to be little affected by microlensing and
that there is little differential extinction between the images. We measure a
revised time-delay between these two images of 152.2 +2.8-3.0 days from R and
V-band data covering 1997 to 2006. This time-delay indicates that the lens has
an approximately flat rotation curve over scales of 1-2 R_e. We also observed
uncorrelated variations of ~0.05 mag/yr which we attribute to microlensing of
the optical emission from the accretion disk. The optical colors have also
changed significantly in the sense that image A is now redder than image B,
rather than bluer as it was in 1993.Comment: 26 page, 6 figures; this version corrects table 1 which reported
incorrect IRAC magnitudes; this change does not affect any result
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