Subaru Telescope adaptive optics observations of gravitationally lensed quasars in the Sloan Digital Sky Survey

We present the results of an imaging observation campaign conducted with the Subaru Telescope adaptive optics system (IRCS+AO188) on 28 gravitationally lensed quasars (23 doubles, 1 quad, and 1 possible triple, and 3 candidates) from the SDSS Quasar Lens Search. We develop a novel modelling technique that fits analytical and hybrid point spread functions (PSFs), while simultaneously measuring the relative astrometry, photometry, as well as the lens galaxy morphology. We account for systematics by simulating the observed systems using separately observed PSF stars. The measured relative astrometry is comparable with that typically achieved with the Hubble Space Telescope, even after marginalizing over the PSF uncertainty. We model for the first time the quasar host galaxies in 5 systems, without a-priory knowledge of the PSF, and show that their luminosities follow the known correlation with the mass of the supermassive black hole. For each system, we obtain mass models far more accurate than those previously published from low-resolution data, and we show that in our sample of lensing galaxies the observed light profile is more elliptical than the mass, for ellipticity > 0.25. We also identify eight doubles for which the sources of external and internal shear are more reliably separated, and should therefore be prioritized in monitoring campaigns aimed at measuring time-delays in order to infer the Hubble constant.

Properties of Weak Lensing Clusters Detected on Hyper Suprime-Cam 2.3 Square Degree Field

We present properties of moderately massive clusters of galaxies detected by the newly developed Hyper Suprime-Cam on the Subaru telescope using weak gravitational lensing. Eight peaks exceeding a S/N ratio of 4.5 are identified on the convergence S/N map of a 2.3 square degree field observed during the early commissioning phase of the camera. Multi-color photometric data is used to generate optically selected clusters using the CAMIRA algorithm. The optical cluster positions were correlated with the peak positions from the convergence map. All eight significant peaks have optical counterparts. The velocity dispersion of clusters are evaluated by adopting the Singular Isothemal Sphere (SIS) fit to the tangential shear profiles, yielding virial mass estimates, M500c, of the clusters which range from 2.7x10^13 to 4.4x10^14 solar mass. The number of peaks is considerably larger than the average number expected from LambdaCDM cosmology but this is not extremely unlikely if one takes the large sample variance in the small field into account. We could, however, safely argue that the peak count strongly favours the recent Planck result suggesting high sigma8$value of 0.83. The ratio of stellar mass to the dark matter halo mass shows a clear decline as the halo mass increases. If the gas mass fraction, fg, in halos is universal, as has been suggested in the literature, the observed baryon mass in stars and gas shows a possible deficit compared with the total baryon density estimated from the baryon oscillation peaks in anisotropy of the cosmic microwave background.

Resolving the Clumpy Structure of the Outflow Winds in the Gravitationally Lensed Quasar SDSS J1029+2623

We study the geometry and the internal structure of the outflowing wind from the accretion disk of a quasar by observing multiple sightlines with the aid of strong gravitational lensing. Using Subaru/HDS, we performed high-resolution ($R$ $sim$ 36,000) spectroscopic observations of images A and B of the gravitationally lensed quasar SDSS J1029+2623 (at $z_{em}$ $sim$ 2.197) whose image separation angle, $theta$ $sim$ 22$^{primeprime}!!$.5, is the largest among those discovered so far. We confirm that the difference in absorption profiles in the images A and B discovered by Misawa et al. (2013) remains unchanged since 2010, implying the difference is not due to time variability of the absorption profiles over the delay between the images, $Delta t$ $sim$ 744 days, but rather due to differences along the sightlines. We also discovered time variation of C IV absorption strength in both images A and B, due to change of ionization condition. If a typical absorbers size is smaller than its distance from the flux source by more than five orders of magnitude, it should be possible to detect sightline variations among images of other smaller separation, galaxy-scale gravitationally lensed quasars.

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.

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.

SDSS J133401.39+331534.3: A New Subarcsecond Gravitationally Lensed Quasar

The quasar SDSS J133401.39+331534.3 at z = 2.426 is found to be a two-image gravitationally lensed quasar with the image separation of 0.833. The object is first identified as a lensed quasar candidate in the Sloan Digital Sky Survey Quasar Lens Search, and then confirmed as a lensed system from follow-up observations at the Subaru and University of Hawaii 2.2-meter telescopes. We estimate the redshift of the lensing galaxy to be 0.557 based on absorption lines in the quasar spectra as well as the color of the galaxy. In particular, we observe the system with the Subaru Telescope AO188 adaptive optics with laser guide star, in order to derive accurate astrometry, which well demonstrates the usefulness of the laser guide star adaptive optics imaging for studying strong lens systems. Our mass modeling with improved astrometry implies that a nearby bright galaxy $sim 4$ apart from the lensing galaxy is likely to affect the lens potential.

The Sloan Digital Sky Survey Quasar Lens Search. IV. Statistical Lens Sample from the Fifth Data Release

We present the second report of our systematic search for strongly lensed quasars from the data of the Sloan Digital Sky Survey (SDSS). From extensive follow-up observations of 136 candidate objects, we find 36 lenses in the full sample of 77,429 spectroscopically confirmed quasars in the SDSS Data Release 5. We then define a complete sample of 19 lenses, including 11 from our previous search in the SDSS Data Release 3, from the sample of 36,287 quasars with i<19.1 in the redshift range 0.6<z<2.2, where we require the lenses to have image separations of 1<theta<20 and i-band magnitude differences between the two images smaller than 1.25 mag. Among the 19 lensed quasars, 3 have quadruple-image configurations, while the remaining 16 show double images. This lens sample constrains the cosmological constant to be Omega_Lambda=0.84^{+0.06}_{-0.08}(stat.)^{+0.09}_{-0.07}(syst.) assuming a flat universe, which is in good agreement with other cosmological observations. We also report the discoveries of 7 binary quasars with separations ranging from 1.1 to 16.6, which are identified in the course of our lens survey. This study concludes the construction of our statistical lens sample in the full SDSS-I data set.

Gravitationally lensed quasars and supernovae in future wide-field optical imaging surveys

Cadenced optical imaging surveys in the next decade will be capable of detecting time-varying galaxy-scale strong gravitational lenses in large numbers, increasing the size of the statistically well-defined samples of multiply-imaged quasars by two orders of magnitude, and discovering the first strongly-lensed supernovae. We carry out a detailed calculation of the likely yields of several planned surveys, using realistic distributions for the lens and source properties and taking magnification bias and image configuration detectability into account. We find that upcoming wide-field synoptic surveys should detect several thousand lensed quasars. In particular, the LSST should find 8000 lensed quasars, 3000 of which will have well-measured time delays, and also ~130 lensed supernovae, which is compared with ~15 lensed supernovae predicted to be found by the JDEM. We predict the quad fraction to be ~15% for the lensed quasars and ~30% for the lensed supernovae. Generating a mock catalogue of around 1500 well-observed double-image lenses, we compute the available precision on the Hubble constant and the dark energy equation parameters for the time delay distance experiment (assuming priors from Planck): the predicted marginalised 68% confidence intervals are sigma(w_0)=0.15, sigma(w_a)=0.41, and sigma(h)=0.017. While this is encouraging in the sense that these uncertainties are only 50% larger than those predicted for a space-based type-Ia supernova sample, we show how the dark energy figure of merit degrades with decreasing knowledge of the the lens mass distribution. (Abridged)

Five New High-Redshift Quasar Lenses from the Sloan Digital Sky Survey

We report the discovery of five gravitationally lensed quasars from the Sloan Digital Sky Survey (SDSS). All five systems are selected as two-image lensed quasar candidates from a sample of high-redshift (z>2.2) SDSS quasars. We confirmed their lensing nature with additional imaging and spectroscopic observations. The new systems are SDSS J0819+5356 (source redshift z_s=2.237, lens redshift z_l=0.294, and image separation theta=4.04), SDSS J1254+2235 (z_s=3.626, theta=1.56), SDSS J1258+1657 (z_s=2.702, theta=1.28), SDSS J1339+1310 (z_s=2.243, theta=1.69), and SDSS J1400+3134 (z_s=3.317, theta=1.74). We estimate the lens redshifts of the latter four systems to be z_l=0.2-0.8 from the colors and magnitudes of the lensing galaxies. We find that the image configurations of all systems are well reproduced by standard mass models. Although these lenses will not be included in our statistical sample of z_s<2.2 lenses, they expand the number of lensed quasars which can be used for high-redshift galaxy and quasar studies.

Analytic models of plausible gravitational lens potentials

Gravitational lenses on galaxy scales are plausibly modelled as having ellipsoidal symmetry and a universal dark matter density profile, with a Sersic profile to describe the distribution of baryonic matter. Predicting all lensing effects requires knowledge of the total lens potential: in this work we give analytic forms for that of the above hybrid model. Emphasising that complex lens potentials can be constructed from simpler components in linear combination, we provide a recipe for attaining elliptical symmetry in either projected mass or lens potential. We also provide analytic formulae for the lens potentials of Sersic profiles for integer and half-integer index. We then present formulae describing the gravitational lensing effects due to smoothly-truncated universal density profiles in cold dark matter model. For our isolated haloes the density profile falls off as radius to the minus fifth or seventh power beyond the tidal radius, functional forms that allow all orders of lens potential derivatives to be calculated analytically, while ensuring a non-divergent total mass. We show how the observables predicted by this profile differ from that of the original infinite-mass NFW profile. Expressions for the gravitational flexion are highlighted. We show how decreasing the tidal radius allows stripped haloes to be modelled, providing a framework for a fuller investigation of dark matter substructure in galaxies and clusters. Finally we remark on the need for finite mass halo profiles when doing cosmological ray-tracing simulations, and the need for readily-calculable higher order derivatives of the lens potential when studying catastrophes in strong lenses.