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Register a new userThe OLS-lens survey: The discovery of five new galaxy-galaxy strong lenses from the SDSS
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Bright galaxy-galaxy strong lenses are much more powerful than lensed quasars for measuring the mass profiles of galaxies, but until this year only a handful have been known. Here we present five new examples, identified via the optimal line-of-sight gravitational lens search strategy applied to luminous red galaxies in the Sloan Digital Sky Survey (SDSS). Our survey largely complements a similar survey by Bolton et al., who recently presented several new lenses. The lensed background galaxies are selected from the SDSS spectra via the presence of narrow emission line signatures, including the [OII] 3726,3729, Hb and [OIII] 4960,5008 lines, superposed on the spectra of the bright, intervening, deflector galaxies. Our five confirmed new systems include deflector galaxies with redshifts z=0.17-0.28 and lensed galaxies with redshifts z=0.47-1.18. Simulations of moderately deep (few orbits) HST-ACS imaging of systems such as these, where the lensed source is brighter than r~23, are presented. These demonstrate the feasibility of measuring accurately the inner slope of the dark matter halo to within an uncertainty sigma(gamma)~0.1, the dark matter fraction within the Einstein radius, and the mass-to-light ratio of the stars alone, independently of dynamical measurements. The high success rate of our search so far, >60%, and the relatively modest observational resources necessary to confirm the gravitational lens nature of the candidates, demonstrate that compilation of a sample of ~100 galaxy-galaxy lenses from the SDSS is readily achievable, opening up a rich new field in dark matter studies.
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Strong gravitational lensing by galaxy clusters magnifies background galaxies, enhancing our ability to discover statistically significant samples of galaxies at z>6, in order to constrain the high-redshift galaxy luminosity functions. Here, we present the first five lens models out of the Reionization Lensing Cluster Survey (RELICS) Hubble Treasury Program, based on new HST WFC3/IR and ACS imaging of the clusters RXC J0142.9+4438, Abell 2537, Abell 2163, RXC J2211.7-0349, and ACT-CLJ0102-49151. The derived lensing magnification is essential for estimating the intrinsic properties of high-redshift galaxy candidates, and properly accounting for the survey volume. We report on new spectroscopic redshifts of multiply imaged lensed galaxies behind these clusters, which are used as constraints, and detail our strategy to reduce systematic uncertainties due to lack of spectroscopic information. In addition, we quantify the uncertainty on the lensing magnification due to statistical and systematic errors related to the lens modeling process, and find that in all but one cluster, the magnification is constrained to better than 20% in at least 80% of the field of view, including statistical and systematic uncertainties. The five clusters presented in this paper span the range of masses and redshifts of the clusters in the RELICS program. We find that they exhibit similar strong lensing efficiencies to the clusters targeted by the Hubble Frontier Fields within the WFC3/IR field of view. Outputs of the lens models are made available to the community through the Mikulski Archive for Space Telescopes
We present a spectroscopic survey for strong galaxy-galaxy lenses. Exploiting optimal sight-lines to massive, bulge-dominated galaxies at redshifts $z sim 0.4$ with wide-field, multifibre spectroscopy, we anticipate the detection of 10-20 lensed Lyman-$alpha$ emitting galaxies at redshifts $z simgreat 3$ from a sample of 2000 deflectors. Initial spectroscopic observations are described and the prospects for constraining the emission-line luminosity function of the Lyman-$alpha$ emitting population are outlined.
We have carried out a systematic search for galaxy-scale strong lenses in multiband imaging from the Hyper Suprime-Cam (HSC) survey. Our automated pipeline, based on realistic strong-lens simulations, deep neural network classification, and visual inspection, is aimed at efficiently selecting systems with wide image separations (Einstein radii ~1.0-3.0), intermediate redshift lenses (z ~ 0.4-0.7), and bright arcs for galaxy evolution and cosmology. We classified gri images of all 62.5 million galaxies in HSC Wide with i-band Kron radius >0.8 to avoid strict pre-selections and to prepare for the upcoming era of deep, wide-scale imaging surveys with Euclid and Rubin Observatory. We obtained 206 newly-discovered candidates classified as definite or probable lenses with either spatially-resolved multiple images or extended, distorted arcs. In addition, we found 88 high-quality candidates that were assigned lower confidence in previous HSC searches, and we recovered 173 known systems in the literature. These results demonstrate that, aided by limited human input, deep learning pipelines with false positive rates as low as ~0.01% can be very powerful tools for identifying the rare strong lenses from large catalogs, and can also largely extend the samples found by traditional algorithms. We provide a ranked list of candidates for future spectroscopic confirmation.
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.
We present the first galaxy scale lens catalog from the second Red-Sequence Cluster Survey. The catalog contains 60 lensing system candidates comprised of Luminous Red Galaxy (LRG) lenses at 0.2 < z < 0.5 surrounded by blue arcs or apparent multiple images of background sources. The catalog is a valuable complement to previous galaxy-galaxy lens catalogs as it samples an intermediate lens redshift range and is composed of bright sources and lenses that allow easy follow-up for detailed analysis. Mass and mass-to-light ratio estimates reveal that the lens galaxies are massive (<M>~5.5x10e11 M_sun/h) and rich in dark matter (<M/L>~14 M_sun/L_sun,B*h). Even though a slight increasing trend in the mass-to-light ratio is observed from z=0.2 to z=0.5, current redshift and light profile measurements do not allow stringent constraints on the mass-to-light ratio evolution of LRGs.
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