Constraints on Small-Scale Structures of Dark Matter from Flux Anomalies in Quasar Gravitational Lenses
R. Benton Metcalf, Adam Amara
备注：
The paper has been extensively revised for version 2 due in part to an error in the code handling the observed data. Additional simulations have been done to strengthen the conclusions which are different than in the original version. 14 pages, 11 figures, submitted to MNRAS
We investigate the statistics of flux anomalies in gravitationally lensed QSOs as a function of dark matter halo properties such as substructure content and halo ellipticity. We do this by creating a very large number of simulated lenses with finite source sizes to compare with the data. After analyzing these simulations, our conclusions are: 1) The finite size of the source is important. The point source approximation commonly used can cause biased results. 2) The widely used R_cusp statistic is sensitive to halo ellipticity as well as the lens' substructure content. 3) For compact substructure, we find new upper bounds on the amount of substructure from the the fact that no simple single-galaxy lenses have been observed with a single source having more than four well separated images. 4) The frequency of image flux anomalies is largely dependent on the total surface mass density in substructures and the size--mass relation for the substructures, and not on the range of substructure masses. 5) Substructure models with the same size--mass relation produce similar numbers of flux anomalies even when their internal mass profiles are different. 6) The lack of high image multiplicity lenses puts a limit on a combination of the substructures' size--mass relation, surface density and mass. 7) Substructures with shallower mass profiles and/or larger sizes produce less extra images. 8) The constraints that we are able to measure here with current data are roughly consistent with \LambdaCDM Nbody simulations.
We report the discovery of a gravitationally lensed quasar identified serendipitously in the Sloan Digital Sky Survey (SDSS). The object, SDSS J094604.90+183541.8, was initially targeted for spectroscopy as a luminous red galaxy, but the SDSS spectrum has the features of both a z=0.388 galaxy and a z=4.8 quasar. We have obtained additional imaging that resolves the system into two quasar images separated by 3.06 arcsec and a bright galaxy that is strongly blended with one of the quasar images. We confirm spectroscopically that the two quasar images represent a single lensed source at z=4.8 wit…
Gravitational lens systems containing lensed quasars are important as cosmological probes, as diagnostics of structural properties of the lensing galaxies and as tools to study the quasars themselves. The largest lensed quasar sample is the SDSS Quasar Lens Search, drawn from the Sloan Digital Sky Survey (SDSS). We are attempting to extend this survey using observations of lens candidates selected from a combination of the quasar sample from the SDSS and the UKIRT Infrared Deep Sky Survey (UKIDSS). This adds somewhat higher image quality together with a wider range of wavelength for the select…
We present the results from nine years of optically monitoring the gravitationally lensed z=0.658 quasar RX J1131-1231. The R-band light curves of the four individual images of the quasar were obtained using deconvolution photometry for a total of 707 epochs. Several sharp quasar variability features strongly constrain the time delays between the quasar images. Using three different numerical techniques, we measure these delays for all possible pairs of quasar images while always processing the four light curves simultaneously. For all three methods, the delays between the three close images A…
We report the discovery of a unique gravitational lens system, SDSSJ2222+2745, producing five spectroscopically confirmed images of a z_s=2.82 quasar lensed by a foreground galaxy cluster at z_l=0.49. We also present photometric and spectroscopic evidence for a sixth lensed image of the same quasar. The maximum separation between the quasar images is 15.1". Both the large image separations and the high image multiplicity of the lensed quasar are in themselves exceptionally rare, and observing the combination of these two factors is an exceptionally unlikely occurrence in present datasets. This…
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 adaptiv…
We report the discovery and confirmation of eight new two-image lensed quasars by the Sloan Digital Sky Survey (SDSS) Quasar Lens Search. The lenses are SDSSJ0904+1512 (image separation θ=1"13, source redshift z_s=1.826), SDSSJ1054+2733 (θ=1"27, z_s=1.452), SDSSJ1055+4628 (θ=1"15, z_s=1.249), SDSSJ1131+1915 (θ=1"46, z_s=2.915), SDSSJ1304+2001 (θ=1"87, z_s=2.175), SDSSJ1349+1227 (θ=3"00, z_s=1.722), SDSSJ1455+1447 (θ=1"73, z_s=1.424), and SDSSJ1620+1203 (θ=2"77, z_s=1.158). Three of them, SDSSJ1055+4628, SDSSJ1455+1447, and SDSSJ1620+1203, satisfy the criteria for constructing our statistical s…
Aims. Within the framework of the COSMOGRAIL collaboration we present 7- and 8.5-year-long light curves and time-delay estimates for two gravitationally lensed quasars: SDSS J1206+4332 and HS 2209+1914. Methods. We monitored these doubly lensed quasars in the R-band using four telescopes: the Mercator, Maidanak, Himalayan Chandra, and Euler Telescopes, together spanning a period of 7 to 8.5 observing seasons from mid-2004 to mid-2011. The photometry of the quasar images was obtained through simultaneous deconvolution of these data. The time delays were determined from these resulting light cur…
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 su…
We study the origin of absorption features on the blue side of the C IV broad emission line of the large-separation lensed quasar SDSS J1029+2623 at z_em ~ 2.197. The quasar images, produced by a foreground cluster of galaxies, have a maximum separation angle of ~ 22".5. The large angular separation suggests that the sight-lines to the quasar central source can go through different regions of outflowing winds from the accretion disk of the quasar, providing a unique opportunity to study the structure of outflows from the accretion disk, a key ingredient for the evolution of quasars as well as …
Gravitational microlensing is a powerful tool for probing the physical properties of quasar accretion disks and properties of the lens galaxy such as its dark matter fraction and mean stellar mass. Unfortunately the number of lensed quasars ($\sim 90$) exceeds our monitoring capabilities. Thus, estimating their microlensing properties is important for identifying good microlensing candidates as well as for the expectations of future surveys. In this work we estimate the microlensing properties of a sample of 87 lensed quasars. While the median Einstein radius crossing time scale is 20.6 years,…
The four-image gravitationally lensed quasar QSO 2237+0305 is microlensed by stars in the lens galaxy. The amplitude of microlensing variability can be used to infer the relative size of the quasar as a function of wavelength; this provides a test of quasar models. Toward this end, we present Spitzer Space Telescope Infrared Spectrograph and Infrared Array Camera (IRAC) observations of QSO 2237+0305, finding the following. (1) The infrared (IR) spectral energy distribution (SED) is similar to that of other bright radio-quiet quasars, contrary to an earlier claim. (2) A dusty torus model with a…
We report the discovery of four doubly imaged quasar lenses. All the four systems are selected as lensed quasar candidates from the Sloan Digital Sky Survey data. We confirm their lensing hypothesis with additional imaging and spectroscopic follow-up observations. The discovered lenses are SDSS J0743+2457 with the source redshift z_s=2.165, the lens redshift z_l=0.381, and the image separation theta=1.034", SDSS J1128+2402 with z_s=1.608 and theta=0.844", SDSS J1405+0959 with z_s=1.810, z_l~0.66, and theta=1.978", and SDSS J1515+1511 with z_s=2.054, z_l=0.742, and theta=1.989". It is difficult…
We apply the iterative MCS deconvolution method (ISMCS) to near-IR HST archives data of seven gravitationally lensed quasars currently monitored by the COSMOGRAIL collaboration: HE 0047-1756, RX J1131-1231, SDSS J1138+0314, SDSS J1155+6346, SDSS J1226-0006, WFI J2026-4536 and HS 2209+1914. In doing so, we obtain relative positions for the lensed images and shape parameters for the light distribution of the lensing galaxy in each system. The lensed image positions are derived with 1-2 mas accuracy. To predict time delays and to test the ability of simple mass models to reproduce the observed co…
We develop a robust method to model quadruply lensed quasars, relying heavily on the work of Witt (1996), who showed that for elliptical potentials, the four image positions, the source, and the lensing galaxy lie on a right hyperbola. For the singular isothermal elliptical potential, there exists a complementary ellipse centered on the source which also maps through the four images, with the same axis ratio as the potential but perpendicular to it. We first solve for Witt's hyperbola, reducing the allowable space of models to three dimensions. We then obtain the best fitting complementary ell…
To use strong gravitational lenses as an astrophysical or cosmological probe, models of their mass distributions are often needed. We present a new, time-efficient automation code for uniform modeling of strongly lensed quasars with GLEE, a lens modeling software, for high-resolution multi-band data. By using the observed positions of the lensed quasars and the spatially extended surface brightness distribution of the lensed quasar host galaxy, we obtain a model of the mass distribution of the lens galaxy. We apply this uniform modeling pipeline to a sample of nine strongly lensed quasars with…
Confirming lensed-quasar candidates with DESI and P200 spectroscopy I. 14 lensed quasars and 8 lensed galaxies
Nanchang University（南昌大学）；Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）；Beijing Normal University（北京师范大学）；University of Hawaiʻi（夏威夷大学）；University of San Francisco（旧金山大学）；National Astronomical Observatories（国家天文台）；University of Science and Technology of China（中国科学技术大学）
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"<θ<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 additio…
We use archival data of NASA's Chandra X-ray telescope to compile an X-ray light curve of all four images of the quadruply lensed quasar Q2237+0305 (z=1.695) from January 2006 to January 2007. We fit simulated point spread functions to the four individual quasar images using Cash's C-statistic to account for the Poisson nature of the X-ray signal. The quasar images display strong flux variations up to a factor of ~4 within one month. We can disentangle the intrinsic quasar variability from flux variations due to gravitational microlensing by looking at the flux ratios of the individual quasar …
We report first results from an ongoing monitoring campaign to measure time delays between the six images of the quasar SDSS\,J2222$+$2745, gravitationally lensed by a galaxy cluster. The time delay between A and B, the two most highly magnified images, is measured to be $τ_{\rm AB} = 47.7 \pm 6.0$ days (95\% confidence interval), consistent with previous model predictions for this lens system. The strong intrinsic variability of the quasar also allows us to derive a time delay value of $τ_{\rm CA} = 722 \pm 24$ days between image C and A, in spite of modest overlap between their light curves …
This paper presents optical R-band light curves and the time delay of the doubly imaged gravitationally lensed quasar SDSS J1001+5027 at a redshift of 1.838. We have observed this target for more than six years, between March 2005 and July 2011, using the 1.2-m Mercator Telescope, the 1.5-m telescope of the Maidanak Observatory, and the 2-m Himalayan Chandra Telescope. Our resulting light curves are composed of 443 independent epochs, and show strong intrinsic quasar variability, with an amplitude of the order of 0.2 magnitudes. From this data, we measure the time delay using five different me…
I describe two novel techniques originally devised to select strongly lensed quasar candidates in wide-field surveys. The first relies on outlier selection in optical and mid-infrared magnitude space; the second combines mid-infrared colour selection with GAIA spatial resolution, to identify multiplets of objects with quasar-like colours. Both methods have already been applied successfully to the SDSS, ATLAS and DES footprints: besides recovering known lenses from previous searches, they have led to new discoveries, including quadruply lensed quasars, which are rare within the rare-object clas…
(abridged) Gravitationally lensed quasars can be used as powerful cosmological and astrophysical probes. We can (i) infer the Hubble constant based on the time-delay technique, (ii) unveil substructures along the l.o.s. toward distant galaxies, and (iii) compare the shape and the slope of baryons and dark matter distributions in galaxies. To reach these goals, we need high-accuracy astrometry and morphology measurements of the lens. In this work, we first present new astrometry for 11 lenses with measured time delays. Using MCS deconvolution on NIC2 HST images, we reached an astrometric accura…
We report the discovery of 13 confirmed two-image quasar lenses from a systematic search for gravitationally lensed quasars in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). We adopted a methodology similar to that used in the SDSS Quasar Lens Search (SQLS). In addition to the confirmed lenses, we report 11 quasar pairs with small angular separations ($\lesssim$2") confirmed from our spectroscopy, which are either projected pairs, physical binaries, or possibly quasar lens systems whose lens galaxies have not yet been detected. The newly discovered quasar lens system, SDSS J1452+…
We examine the wavelength dependence of flux ratios for six gravitationally lensed quasars using K and L' images obtained at the Gemini North 8m telescope. We select lenses with source redshifts z_s < 2.8 so that K-band images probe rest-frame optical emission from accretion disks, while L'-band images probe rest-frame near-infrared flux emitted (in part) from the more extended surrounding torus. Since the observations correspond to different source sizes, the K and L' flux ratios are sensitive to structure on different scales and may be useful for studying small-structure in the lens galaxies…
We report the discovery of a pair of quasars at $z=1.487$, 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 $z=0.899$. 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 gravitati…
We present 11.2 micron observations of the gravitationally lensed, radio-loud z_s=2.64 quasar MG0414+0534, obtained using the Michelle camera on Gemini North. We find a flux ratio anomaly of A2/A1= 0.93 +/- 0.02 for the quasar images A1 and A2. When combined with the 11.7 micron measurements from Minezaki et al. (2009), the A2/A1 flux ratio is nearly 5-sigma from the expected ratio for a model based on the two visible lens galaxies. The mid-IR flux ratio anomaly can be explained by a satellite (substructure), 0.3" Northeast of image A2, as can the detailed VLBI structures of the jet produced b…
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 wo…
We present an analysis of archival observations with the Atacama Large (sub-)Millimetre Array (ALMA) of the gravitationally lensed quasar MG J0414+0534, which show four compact images of the quasar and an Einstein ring from the dust associated with the quasar host galaxy. We confirm that the flux-ratio anomalies observed in the mid-infrared and radio persists into the sub-mm for the continuum images of the quasar. We report the detection of CO (11-10) spectral line emission, which traces a region of compact gas around the quasar nucleus. This line emission also shows evidence of a flux-ratio a…
We report the discovery of the quadruply lensed quasar J1433+6007, mined in the SDSS DR12 photometric catalogues using a novel outlier-selection technique, without prior spectroscopic or UV excess information. Discovery data obtained at the Nordic Optical telescope (NOT, La Palma) show nearly identical quasar spectra at $z_s=2.74$ and four quasar images in a fold configuration, one of which sits on a blue arc. The deflector redshift is $z_{l}=0.407,$ from Keck-ESI spectra. We describe the selection procedure, discovery and follow-up, image positions and $BVRi$ magnitudes, and first results and…
SDSS J2222+2745 is a galaxy cluster at z=0.49, strongly lensing a quasar at z=2.805 into six widely separated images. In recent HST imaging of the field, we identify additional multiply lensed galaxies, and confirm the sixth quasar image that was identified by Dahle et al. (2013). We used the Gemini North telescope to measure a spectroscopic redshift of z=4.56 of one of the secondary lensed galaxies. These data are used to refine the lens model of SDSS J2222+2745, compute the time delay and magnifications of the lensed quasar images, and reconstruct the source image of the quasar host and a se…
We have scanned 5000 deg$^{2}$ of Southern Sky to search for strongly lensed quasars with five methods, all source-oriented, but based on different assumptions and selection criteria. We analyse morphological searches based on Gaia multiplet detection and chromatic offsets, fibre-spectroscopic preselection, and X-ray and radio preselection. The performance and complementarity of the methods are evaluated on a common sample of known lenses in the Dark Energy Survey public DR1 footprint. We recovered in total 13 known lenses, of which 8 quadruplets. The method that found the largest number of kn…
Gravitationally lensed quasars are useful for studying astrophysics and cosmology, and enlarging the sample size of lensed quasars is important for multiple studies. In this work, we develop a lens search algorithm for four-image (quad) lensed quasars based on their time variability. In the development of the lens search algorithm, we constructed a pipeline simulating multi-epoch images of lensed quasars in cadenced surveys, accounting for quasar variabilities, quasar hosts, lens galaxies, and the PSF variation. Applying the simulation pipeline to the Hyper Suprime-Cam (HSC) transient survey, …
The cold dark matter scenario of hierarchical large-scale structure formation predicts the existence of abundant subhalos around large galaxies. However, the number of observed dwarf galaxies is far from this theoretical prediction, suggesting that most of the subhalos could be dark or quite faint. Gravitational lensing is a powerful tool to probe the mass distribution directly irrespective of whether it is visible or dark. Time delay anomalies in strongly lensed quasar systems are complementary to flux ratio anomalies in probing dark matter substructure in galaxies. Here we propose that lense…
We report the serendipitous discovery of the first gravitationally lensed quasar candidate from Pan-STARRS. The grizy images reveal four point-like images with magnitudes between 14.9 mag and 18.1 mag. The colors of the point sources are similar, and they are more consistent with quasars than with stars or galaxies. The lensing galaxy is detected in the izy bands, with an inferred photometric redshift of ~0.6, lower than that of the point sources. We successfully model the system with a singular isothermal ellipsoid with shear, using the relative positions of the five objects as constraints. W…
Semi-Supervised Learning for Lensed Quasar Detection
Donald Bren School of Information and Computer Sciences, University of California, Irvine（加州大学尔湾分校唐纳德布伦信息与计算机科学学院）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；CSIRO Data61（澳大利亚联邦科学与工业研究组织数据61）；California Institute of Technology（加州理工学院）；Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS（波尔多大学CNRS天体物理实验室）；Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo（圣保罗大学天文、地球物理与大气科学研究所）
We report on discovery results from a quasar lens search in the ATLAS public footprint, extending quasar lens searches to a regime without $u-$band or fiber-spectroscopic information, using a combination of data mining techniques on multi-band catalog magnitudes and image-cutout modelling. Spectroscopic follow-up campaigns, conducted at the 2.6m Nordic Optical Telescope (La Palma) and 3.6m New Technology Telescope (La Silla) in 2016, yielded seven pairs of quasars exhibiting the same lines at the same redshift and monotonic flux-ratios with wavelength (hereafter NIQs, Nearly Identical Quasar p…
We present a microlensing analysis of 61 Chandra observations of 14 quadruply lensed quasars. X-ray flux measurements of the individual quasar images give a clean determination of the microlensing effects in the lensing galaxy and thus offer a direct assessment of the local fraction of stellar matter making up the total integrated mass along the lines of sight through the lensing galaxy. A Bayesian analysis of the ensemble of lensing galaxies gives a most likely local stellar fraction of 7%, with the other 93% in a smooth, dark matter component, at an average impact parameter R_c of 6.6 kpc fr…
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, $θ$ $\sim$ 22$^{\prime\prime}\!\!$.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. (20…
Context. Strong gravitationally lensed quasars are among the most interesting and useful observable extragalactic phenomena. Because their study constitutes a unique tool in various fields of astronomy, they are highly sought, not without difficulty. Indeed, even in this era of all-sky surveys, their recognition remains a great challenge, with barely a few hundred currently known systems. Aims. In this work we aim to detect new strongly lensed quasar candidates in the recently published Gaia Data Release 2 (DR2), which is the highest spatial resolution astrometric and photometric all-sky surve…
In the framework of the Gravitational LENses and DArk MAtter (GLENDAMA) project, we present a database of nine gravitationally lensed quasars (GLQs) that have two or four images brighter than $r$ = 20 mag and are located in the northern hemisphere. This new database consists of a rich variety of follow-up observations included in the GLENDAMA global archive, which is publicly available online and contains 6557 processed astronomical frames of the nine lens systems over the period 1999$-$2016. In addition to the GLQs, our archive also incorporates binary quasars, accretion-dominated radio-loud …
The flux ratios in the multiple images of gravitationally lensed quasars can provide evidence for dark matter substructure in the halo of the lensing galaxy if the flux ratios differ from those predicted by a smooth model of the lensing galaxy mass distribution. However, it is also possible that baryonic structures in the lensing galaxy, such as edge-on discs, can produce flux-ratio anomalies. In this work, we present the first statistical analysis of flux-ratio anomalies due to baryons from a numerical simulation perspective. We select galaxies with various morphological types in the Illustri…
We observed six strongly lensed, radio-loud quasars (MG 0414+0534, CLASS B0712+472, JVAS B1030+074, CLASS B1127+385, CLASS B1152+199, and JVAS B1938+666) in order to identify systems suitable for measuring cosmological parameters using time delays between their multiple images. These systems are in standard two and four image configurations, with B1938 having a faint secondary pair of images. Two separate monitoring campaigns were carried out using the VLA and upgraded JVLA. Lightcurves were extracted for each individual lensed image and analyzed for signs of intrinsic variability. While it wa…
