Search

We present the discovery and preliminary characterisation of two high-redshift gravitationally lensed quasar systems in Gaia Data Release 2 (DR2). Candidates with multiple close-separation Gaia detections and quasar-like colours in WISE, Pan-STARRS, and DES are selected for follow-up spectroscopy with the New Technology Telescope. We confirm DES J215028.71−465251.3 as a $z$ = 4.130 ± 0.006 asymmetric, doubly imaged lensed quasar system and model the lensing mass distribution as a singular isothermal sphere. The system has an Einstein radius of 1.202 ± 0.005 arcsec and a predicted time delay of ∼122.0 d between the quasar images, assuming a lensing galaxy redshift of $z$ = 0.5, making this a priority system for future optical monitoring. We confirm PS J042913.17+142840.9 as a $z$ = 3.866 ± 0.003 four-image quasar system in a cusp configuration, lensed by two foreground galaxies. The system is well modelled using a singular isothermal ellipsoid for the primary lens and a singular isothermal sphere for the secondary lens with Einstein radii 0.704 ± 0.006 and 0.241 ± 0.030 arcsec, respectively. A maximum predicted time delay of 9.6 d is calculated, assuming lensing galaxy redshifts of $z$ = 1.0. Furthermore, PS J042913.17+142840.9 exhibits a large flux ratio anomaly, up to a factor of 2.66 ± 0.37 in i band, that varies across optical and near-infrared wavelengths. We discuss LSST and its implications for future high-redshift lens searches and outline an extension to the search using supervised machine learning techniques.

The generation-defining Vera C. Rubin Observatory will make state-of-the-art measurements of both the static and transient universe through its Legacy Survey for Space and Time (LSST). With such capabilities, it is immensely challenging to optimize the LSST observing strategy across the survey's wide range of science drivers. Many aspects of the LSST observing strategy relevant to the LSST Dark Energy Science Collaboration, such as survey footprint definition, single visit exposure time and the cadence of repeat visits in different filters, are yet to be finalized. Here, we present metrics used to assess the impact of observing strategy on the cosmological probes considered most sensitive to survey design; these are large-scale structure, weak lensing, type Ia supernovae, kilonovae and strong lens systems (as well as photometric redshifts, which enable many of these probes). We evaluate these metrics for over 100 different simulated potential survey designs. Our results show that multiple observing strategy decisions can profoundly impact cosmological constraints with LSST; these include adjusting the survey footprint, ensuring repeat nightly visits are taken in different filters and enforcing regular cadence. We provide public code for our metrics, which makes them readily available for evaluating further modifications to the survey design. We conclude with a set of recommendations and highlight observing strategy factors that require further research., Comment: 49 pages, 17 figures

The paper ‘Is every strong lens model unhappy in its own way? Uniform modelling of a sample of 13 quadruply+ imaged quasars’ was published in MNRAS, 483, 4, 5649–5671 (2019). The coordinate values of the image positions in table 4 were wrongly printed due to a clerical error. At a later stage of writing the manuscript, we have changed the zero-point definition of the lens coordinate systems, but the relative image positions were not accounted for this change of definition while printing out table 4. We provide the updated Table 4 below. This error does not impact any other results of the paper in any way, except for the table itself. We thank Collin Werner and Paul Schechter for helping us identify this error.

Vera C. Rubin Observatory is a ground-based astronomical facility under construction, a joint project of the National Science Foundation and the U.S. Department of Energy, designed to conduct a multi-purpose 10-year optical survey of the southern hemisphere sky: the Legacy Survey of Space and Time. Significant flexibility in survey strategy remains within the constraints imposed by the core science goals of probing dark energy and dark matter, cataloging the Solar System, exploring the transient optical sky, and mapping the Milky Way. The survey's massive data throughput will be transformational for many other astrophysics domains and Rubin's data access policy sets the stage for a huge potential users' community. To ensure that the survey science potential is maximized while serving as broad a community as possible, Rubin Observatory has involved the scientific community at large in the process of setting and refining the details of the observing strategy. The motivation, history, and decision-making process of this strategy optimization are detailed in this paper, giving context to the science-driven proposals and recommendations for the survey strategy included in this Focus Issue., Submitted as the opening paper of the Astrophysical Journal Focus Issue on Rubin LSST cadence and survey strategy

Gravitationally lensed quasars are valuable, but extremely rare, probes of observational cosmology and extragalactic astrophysics. Progress in these fields has been limited just by the paucity of systems with good ancillary data. Here we present a first spectroscopic confirmation of lenses discovered in the Southern Sky from the DES and KiDS-DR3 footprints. % optical ground based surveys in the Southern Hemisphere. We have targeted 7 high-graded candidates, selected with new techniques, with NTT-EFOSC2, and confirmed 5 of them. We provide source spectroscopic redshifts, image separations, $gri$ photometry and first lens model parameters. The success rate of ~70% confirms our forecasts, based on the comparison between the number of candidate doubles and quadruplets in our searches over a ~5000 sq.deg footprint and theoretical predictions., Comment: 6 pages, 5 figures. Accepted for publication to MNRAS

We present spectroscopic confirmation of three new two-image gravitationally lensed quasars, compiled from existing strong lens and X-ray catalogs. Images of HSC J091843.27$-$022007.5 show a red galaxy with two blue point sources at either side, separated by 2.26 arcsec. This system has a source and a lens redshifts $z_s=0.804$ and $z_{\ell}=0.459$, respectively, as obtained by our follow-up spectroscopic data. CXCO J100201.50$+$020330.0 shows two point sources separated by 0.85 arcsec on either side of an early-type galaxy. The follow-up spectroscopic data confirm the fainter quasar has the same redshift with the brighter quasar from the SDSS fiber spectrum at $z_s=2.016$. The deflecting foreground galaxy is a typical early-type galaxy at a redshift of $z_{\ell}=0.439$. SDSS J135944.21$+$012809.8 has two point sources with quasar spectra at the same redshift $z_s=1.096$, separated by 1.05 arcsec, and fits to the HSC images confirm the presence of a galaxy between these. These discoveries demonstrate the power of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP)'s deep imaging and wide sky coverage. Combined with existing X-ray source catalogues and follow-up spectroscopy, the HSC-SSP provides us unique opportunities to find multiple-image quasars lensed by a foreground galaxy., Comment: Accepted for publication in MNRAS, 7 pages, 3 figures (add credit to Claude Cornen)

We report the results of the STRong lensing Insights from the Dark Energy Survey (STRIDES) follow-up campaign of the late 2017/early 2018 season. We obtained spectra of 65 lensed quasar candidates either with EFOSC2 on the NTT or ESI on Keck, which confirm 10 new gravitationally lensed quasars and 10 quasar pairs with similar spectra, but which do not show a lensing galaxy in DES images. Eight lensed quasars are doubly imaged with source redshifts between 0.99 and 2.90, one is triply imaged by a group (DESJ0345-2545, $z=1.68$), and one is quadruply imaged (quad: DESJ0053-2012, $z=3.8$). Singular isothermal ellipsoid models for the doubles, based on high-resolution imaging from SAMI on SOAR or NIRC2 on Keck, give total magnifications between 3.2 and 5.6, and Einstein radii between 0.49 and 1.97 arcseconds. After spectroscopic follow-up, we extract multi-epoch $grizY$ photometry of confirmed lensed quasars and contaminant quasar+star pairs from the first 4 years of DES data using parametric multi-band modelling, and compare variability in each system's components. By measuring the reduced ${\chi}^2$ associated with fitting all epochs to the same magnitude, we find a simple cut on the less variable component that retains all confirmed lensed quasars, while removing 94 per cent of contaminant systems with stellar components. Based on our spectroscopic follow-up, this variability information can improve selection of lensed quasars and quasar pairs from 34-45 per cent to 51-70 per cent, with the majority of remaining contaminants being compact star-forming galaxies. Using mock lensed quasar lightcurves we demonstrate that selection based only on variability will over-represent the quad fraction by 10 per cent over a complete DES magnitude-limited sample (excluding microlensing differences), explained by the magnification bias and hence lower luminosity (more variable) sources in quads., Comment: 22 pages, 16 figures, submitted to MNRAS

The magnifications of compact-source lenses are extremely sensitive to the presence of low mass dark matter halos along the entire sight line from the source to the observer. Traditionally, the study of dark matter structure in compact-source strong gravitational lenses has been limited to radio-loud systems, as the radio emission is extended and thus unaffected by microlensing which can mimic the signal of dark matter structure. An alternate approach is to measure quasar nuclear-narrow line emission, which is free from microlensing and present in virtually all quasar lenses. In this paper, we double the number of systems which can be used for gravitational lensing analyses by presenting measurements of narrow-line emission from a sample of 8 quadruply imaged quasar lens systems, WGD J0405-3308, HS 0810+2554, RX J0911+0551, SDSS J1330+1810, PS J1606-2333, WFI 2026-4536, WFI 2033-4723 and WGD J2038-4008. We describe our updated grism spectral modelling pipeline, which we use to measure narrow-line fluxes with uncertainties of 2-10\%, presented here. We fit the lensed image positions with smooth mass models and demonstrate that these models fail to produce the observed distribution of image fluxes over the entire sample of lenses. Furthermore, typical deviations are larger than those expected from macromodel uncertainties. This discrepancy indicates the presence of perturbations caused by small-scale dark matter structure. The interpretation of this result in terms of dark matter models is presented in a companion paper., Accepted for publication in MNRAS

We present a tool to generate mock quasar microlensing light curves and sample them according to any observing strategy. An updated treatment of the fixed and random velocity components of observer, lens, and source is used, together with a proper alignment with the external shear defining the magnification map caustic orientation. Our tool produces quantitative results on high magnification events and caustic crossings, which we use to study three lensed quasars known to display microlensing, viz. RX J1131-1231, HE 0230-2130, and Q 2237+0305, as they would be monitored by The Rubin Observatory Legacy Survey of Space and Time (LSST). We conclude that depending on the location on the sky, the lens and source redshift, and the caustic network density, the microlensing variability may deviate significantly than the expected $\sim$20-year average time scale (Mosquera & Kochanek 2011, arXiv:1104.2356). We estimate that $\sim300$ high magnification events with $��$mag$>1$ mag could potentially be observed by LSST each year. The duration of the majority of high magnification events is between 10 and 100 days, requiring a very high cadence to capture and resolve them. Uniform LSST observing strategies perform the best in recovering microlensing high magnification events. Our web tool can be extended to any instrument and observing strategy, and is freely available as a service at http://gerlumph.swin.edu.au/tools/lsst_generator/, along with all the related code., 10 pages, 6 figures, 2 tables. Published in MNRAS. Updated Table 1

Full author list: A J Shajib, S Birrer, T Treu, A Agnello, E J Buckley-Geer, J H H Chan, L Christensen, C Lemon, H Lin, M Millon, J Poh, C E Rusu, D Sluse, C Spiniello, G C-F Chen, T Collett, F Courbin, C D Fassnacht, J Frieman, A Galan, D Gilman, A More, T Anguita, M W Auger, V Bonvin, R McMahon, G Meylan, K C Wong, T M C Abbott, J Annis, S Avila, K Bechtol, D Brooks, D Brout, D L Burke, A Carnero Rosell, M Carrasco Kind, J Carretero, F J Castander, M Costanzi, L N da Costa, J De Vicente, S Desai, J P Dietrich, P Doel, A Drlica-Wagner, A E Evrard, D A Finley, B Flaugher, P Fosalba, J García-Bellido, D W Gerdes, D Gruen, R A Gruendl, J Gschwend, G Gutierrez, D L Hollowood, K Honscheid, D Huterer, D J James, T Jeltema, E Krause, N Kuropatkin, T S Li, M Lima, N MacCrann, M A G Maia, J L Marshall, P Melchior, R Miquel, R L C Ogando, A Palmese, F Paz-Chinchón, A A Plazas, A K Romer, A Roodman, M Sako, E Sanchez, B Santiago, V Scarpine, M Schubnell, D Scolnic, S Serrano, I Sevilla-Noarbe, M Smith, M Soares-Santos, E Suchyta, G Tarle, D Thomas, A R Walker, Y Zhang, We present a blind time-delay cosmographic analysis for the lens system DES J0408-5354. This system is extraordinary for the presence of two sets of multiple images at different redshifts, which provide the opportunity to obtain more information at the cost of increased modelling complexity with respect to previously analysed systems. We perform detailed modelling of the mass distribution for this lens system using three band Hubble Space Telescope imaging. We combine the measured time delays, line-of-sight central velocity dispersion of the deflector, and statistically constrained external convergence with our lens models to estimate two cosmological distances. We measure the 'effective' time-delay distance corresponding to the redshifts of the deflector and the lensed quasar DΔ t eff=3382-115+146 Mpc and the angular diameter distance to the deflector Dd = 1711-280+376 Mpc, with covariance between the two distances. From these constraints on the cosmological distances, we infer the Hubble constant H0= 74.2-3.0+2.7 km s-1 Mpc-1 assuming a flat ΛCDM cosmology and a uniform prior for ωm as \Omega m ∼ \mathcal {U(0.05, 0.5). This measurement gives the most precise constraint on H0 to date from a single lens. Our measurement is consistent with that obtained from the previous sample of six lenses analysed by the H0 Lenses in COSMOGRAIL's Wellspring (H0LiCOW) collaboration. It is also consistent with measurements of H0 based on the local distance ladder, reinforcing the tension with the inference from early Universe probes, for example, with 2.2σ discrepancy from the cosmic microwave background measurement., TT acknowledges support by the Packard Foundation through a Packard Research fellowship and by the National Science Foundation through NSF grants AST-1714953 and AST-1906976. This project is partly funded by the Danish council for independent research under the project ‘Fundamentals of Dark Matter Structures’, DFF - 6108-00470. AA was supported by a grant from VILLUM FONDEN (project number 16599). JHHC, MM, CL, DS, FC, and AG acknowledge support from the Swiss National Science Foundation (SNSF) and by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (COSMICLENS: grant agreement No 787866). CS has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie actions grant agreement No 664931. GCFC acknowledges support from the Ministry of Education in Taiwan via Government Scholarship to Study Abroad (GSSA). CDF and GCFC acknowledge support for this work from the National Science Foundation under Grant No AST-1715611. TA acknowledges support from Proyecto FONDECYT N○ 1190335. KCW was supported by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan. This work used computational and storage services associated with the Hoffman2 Shared Cluster provided by UCLA Institute for Digital Research and Education’s Research Technology Group. This work used the Extreme Science and Engineering Discovery Environment (XSEDE) through allocation TG-AST190038, which is supported by National Science Foundation grant number ACI-1548562 (Towns et al. 2014). Specifically, this work used the Comet and Oasis system at the San Diego Supercomputer Center (SDSC), and the Bridges system, which is supported by NSF award number ACI-1445606, at the Pittsburgh Supercomputing Center (PSC, Nystrom et al. 2015). AJS thanks Smadar Naoz for providing access to additional computing nodes on the Hoffman2 Shared Cluster and Khalid Jawed for assisting with additional computational resources from the Structures–Computer Interaction Laboratory at UCLA. The DES data management system is supported by the National Science Foundation under Grant Numbers AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2015-71825, ESP2015-66861, FPA2015-68048, SEV-2016-0588, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Program (FP7/2007-2013) including ERC grant agreements 240672, 291329, and 306478. We acknowledge support from the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020, and the Brazilian Instituto Nacional de Ciência e Tecnologia (INCT) e-Universe (CNPq grant 465376/2014-2).

The DES Collaboration: et al., In time-delay cosmography, three of the key ingredients are (1) determining the velocity dispersion of the lensing galaxy, (2) identifying galaxies and groups along the line of sight with sufficient proximity and mass to be included in the mass model, and (3) estimating the external convergence κext from less massive structures that are not included in the mass model. We present results on all three of these ingredients for two time-delay lensed quad quasar systems, DES J0408–5354 and WGD 2038–4008 . We use the Gemini, Magellan, and VLT telescopes to obtain spectra to both measure the stellar velocity dispersions of the main lensing galaxies and to identify the line-of-sight galaxies in these systems. Next, we identify 10 groups in DES J0408–5354 and two groups in WGD 2038–4008 using a group-finding algorithm. We then identify the most significant galaxy and galaxy-group perturbers using the ‘flexion shift’ criterion. We determine the probability distribution function of the external convergence κext for both of these systems based on our spectroscopy and on the DES-only multiband wide-field observations. Using weighted galaxy counts, calibrated based on the Millennium Simulation, we find that DES J0408–5354 is located in a significantly underdense environment, leading to a tight (width ∼3 per cent⁠), negative-value κext distribution. On the other hand, WGD 2038–4008 is located in an environment of close to unit density, and its low source redshift results in a much tighter κext of ∼1 per cent⁠, as long as no external shear constraints are imposed., JP would like to thank Gourav Khullar for his help and insightful discussions that helped improve the analysis in this paper. This work made use of computing resources and support provided by the Research Computing Center at the University of Chicago. JP is supported in part by the Kavli Institute for Cosmological Physics at the University of Chicago through grant NSF PHY-1125897 and an endowment from the Kavli Foundation and its founder Fred Kavli. AJS was supported by the National Aeronautics and Space Administration (NASA) through the Space Telescope Science Institute (STScI) grant HST-GO-15320. AJS was also supported by the Dissertation Year Fellowship from the University of California, Los Angeles (UCLA) graduate division. TA acknowledges support from Proyecto FONDECYT N: 1190335. This work was supported by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan. CDF acknowledges support for this work from the National Science Foundation under Grant No. AST-1715611. SM acknowledges the funding from the European Research Council (ERC) under the EUs Horizon 2020 research and innovation program (COSMICLENS; grant agreement No. 787886). Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência, Tecnologia e Inovação, the Deutsche Forschungsgemeinschaft and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgenössische Technische Hochschule (ETH) Zürich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ciències de l’Espai (IEEC/CSIC), the Institut de Física d’Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universität München and the associated Excellence Cluster Universe, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, The Ohio State University, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, Texas A&M University, and the OzDES Membership Consortium. Based in part on observations at Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. The DES data management system is supported by the National Science Foundation under Grant Numbers AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2015-71825, ESP2015-88861, FPA2015-68048, SEV-2012-0234, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Program (FP7/2007-2013) including ERC grant agreements 240672, 291329, and 306478. We acknowledge support from the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020. This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.

The primary goals of the STRong lensing Insights into the Dark Energy Survey (STRIDES) collaboration are to measure the dark energy equation of state parameter and the free streaming length of dark matter. To this aim, STRIDES is discovering strongly lensed quasars in the imaging data of the Dark Energy Survey and following them up to measure time delays, high resolution imaging, and spectroscopy sufficient to construct accurate lens models. In this paper, we first present forecasts for STRIDES. Then, we describe the STRIDES classification scheme, and give an overview of the Fall 2016 follow-up campaign. We continue by detailing the results of two selection methods, the outlier selection technique and a morphological algorithm, and presenting lens models of a system that could possibly be a lensed quasar in an unusual configuration. We conclude with the summary statistics of the Fall 2016 campaign. Including searches presented in companion papers (Anguita et al.; Ostrovski et al.), STRIDES followed up 117 targets identifying 7 new strongly lensed systems, and 7 nearly identical quasars, which could be confirmed as lenses by the detection of the lens galaxy. 76 candidates were rejected and 27 remain otherwise inconclusive, for a success rate in the range of 6-35 per cent. This rate is comparable to that of previous searches like SDSS Quasar Lens Search even though the parent data set of STRIDES is purely photometric and our selection of candidates cannot rely on spectroscopic information., TT and VM acknowledge support by the David and Lucille Packard Foundation through a Packard Research Fellowship to TT. TT acknowledges support by the National Science Foundation through grants AST- 1450141 and AST-1714953. CDF and GCFC acknowledge support from the National Science Foundation through grants AST-1312329 and AST-1715611. TA and YA acknowledge support by proyecto FONDECYT 11130630 and by the Ministry for the Economy, Development, and Tourism’s Programa Inicativa Científica Milenio through grant IC 12009, awarded to The Millennium Institute of Astrophysics (MAS). FC, VB, and JC acknowledge support from the Swiss National Science Foundation. SHS thanks the Max Planck Society for support through the Max Planck Research Group

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 pairs). The quasar redshifts range between $\approx1.2$ and $\approx 2.7;$ contaminants are typically pairs of bright blue stars, quasar-star alignments along the line of sight, and narrow-line galaxies at $0.3, Comment: MNRAS subm. 14/09/17. Revised version after first referee report

One of the primary mission objectives for the Roman Space Telescope is to investigate the nature of dark energy with a variety of methods. Observations of Type Ia supernovae (SNIa) will be one of the principal anchors of the Roman cosmology program, through traditional luminosity distance measurements. This SNIa cosmology program can provide another valuable cosmological probe, without altering the mission strategy: time delay cosmography with gravitationally lensed SN. In this work, we forecast lensed SN cosmology constraints with the Roman Space Telescope, while providing useful tools for future work. Using anticipated characteristics of the Roman SNIa survey, we have constructed mock catalogs of expected resolved lensing systems, as well as strongly lensed Type Ia and core-collapse (CC) SN light curves, including microlensing effects. We predict Roman will find ~11 lensed SNIa and ~20 CCSN, dependent on the survey strategy. Next, we estimate the time delay precision obtainable with Roman (Ia: ~2 days, CC: ~3 days), and use a Fisher matrix analysis to derive projected constraints on $H_0$,$\Omega_m$, and the dark energy Equation of State (EOS), $w$, for each SNIa survey strategy. A strategy optimized for high-redshift SNIa discovery is preferred when considering the constraints possible from both SNIa and lensed SN cosmology, also delivering ~1.5 times more lensed SN than other proposed survey strategies., Comment: Accepted Version (ApJ, 1/4/21)

We present six new time-delay measurements obtained from Rc-band monitoring data acquired at the Max Planck Institute for Astrophysics (MPIA) 2.2 m telescope at La Silla observatory between October 2016 and February 2020. The lensed quasars HE 0047−1756, WG 0214−2105, DES 0407−5006, 2M 1134−2103, PSJ 1606−2333, and DES 2325−5229 were observed almost daily at high signal-to-noise ratio to obtain high-quality light curves where we can record fast and small-amplitude variations of the quasars. We measured time delays between all pairs of multiple images with only one or two seasons of monitoring with the exception of the time delays relative to image D of PSJ 1606−2333. The most precise estimate was obtained for the delay between image A and image B of DES 0407−5006, where τAB = −128.4−3.8+3.5 d (2.8% precision) including systematics due to extrinsic variability in the light curves. For HE 0047−1756, we combined our high-cadence data with measurements from decade-long light curves from previous COSMOGRAIL campaigns, and reach a precision of 0.9 d on the final measurement. The present work demonstrates the feasibility of measuring time delays in lensed quasars in only one or two seasons, provided high signal-to-noise ratio data are obtained at a cadence close to daily.

The Hubble Frontier Fields offer an exceptionally deep window into the high-redshift universe, covering a substantially larger area than the Hubble Ultra-Deep field at low magnification and probing 1--2 mags deeper in exceptional high-magnification regions. We aim to leverage Atacama Large Millimetre Array (ALMA) band 6 ($\approx$263\,GHz) mosaics in the central portions of five Frontier Fields to characterize the infrared (IR) properties of $1582$ ultraviolet (UV)-selected Lyman-Break Galaxies (LBGs) at redshifts of $z {\sim}$2--8. We investigated individual and stacked fluxes and IR excess (IRX) values of the LBG sample as functions of stellar mass ($\mathrm{M}_{\bigstar}$), redshift, UV luminosity and slope $\beta$, and lensing magnification. Two (2) LBG candidates were individually detected above a significance of $4.1{-}\sigma$, while stacked samples of the remaining LBG candidates yielded no significant detections. We investigated our detections and upper limits in the context of the IRX-$\mathrm{M}_{\bigstar}$ and IRX-$\beta$ relations, probing at least one dex lower in stellar mass than past studies have done. Our upper limits exclude substantial portions of parameter space and they are sufficiently deep in a handful of cases to create mild tension with the typically assumed attenuation and consensus relations. We observe a clear and smooth trend between $\mathrm{M}_{\bigstar}$ and $\beta$, which extends to low masses and blue (low) $\beta$ values, consistent with expectations from previous works., Comment: Accepted for publication in A&A, 28 pages and 20 figures. Full versions of Tables C.1, C.2, C.3, C.4, and C.5 are available for download at http://astro.puc.cl/~rcarvaja/docs/tables_ALMA_FF_V_RCP.tar.gz

We present time-delay estimates for the quadruply imaged quasar PG 1115+080. Our resuls are based on almost daily observations for seven months at the ESO MPIA 2.2m telescope at La Silla Observatory, reaching a signal-to-noise ratio of about 1000 per quasar image. In addition, we re-analyse existing light curves from the literature that we complete with an additional three seasons of monitoring with the Mercator telescope at La Palma Observatory. When exploring the possible source of bias we consider the so-called microlensing time delay, a potential source of systematic error so far never directly accounted for in previous time-delay publications. In fifteen years of data on PG 1115+080, we find no strong evidence of microlensing time delay. Therefore not accounting for this effect, our time-delay estimates on the individual data sets are in good agreement with each other and with the literature. Combining the data sets, we obtain the most precise time-delay estimates to date on PG 1115+080, with Dt(AB) = 8.3+1.5-1.6 days (18.7% precision), Dt(AC) = 9.9+1.1-1.1 days (11.1%) and Dt(BC) = 18.8+1.6-1.6 days (8.5%). Turning these time delays into cosmological constraints is done in a companion paper that makes use of ground-based Adaptive Optics (AO) with the Keck telescope., 15 pages, 6 figures, submitted to A&A. Comments welcome

Indexación: Scopus. DGG acknowledges support from the National Research Foundation of South Africa. Support for LFB and TA is provided by the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. LI and LFB are in part supported by CONICYT-Chile grant Basal-CATA PFB-06/2007. HKCYacknowledge support for this project from a Discovery Grant from the National Science and Engineering Research Council of Canada and grants from the Canada Research Chair Program. MC's research is supported by the Transregional Collaborative Research Centre TRR 33. This paper includes data gathered with the 6.5-m Magellan Telescopes located at Las Campanas Observatory, Chile. This paper also includes data based on observations obtained at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, University of Cambridge, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University. We present follow-up spectroscopic observations of galaxy clusters from the first Red-sequence Cluster Survey (RCS-1). This work focuses on two samples, a lower redshift sample of ~30 clusters ranging in redshift from z~0.2-0.6 observedwith multiobject spectroscopy (MOS) on 4-6.5-m class telescopes and a z ~ 1 sample of ~10 clusters 8-m class telescope observations. We examine the detection efficiency and redshift accuracy of the now widely used redsequence technique for selecting clusters via overdensities of red-sequence galaxies. Using both these data and extended samples including previously published RCS-1 spectroscopy and spectroscopic redshifts from SDSS, we find that the red-sequence redshift using simple twofilter cluster photometric redshifts is accurate to σz ≈ 0.035(1 + z) in RCS-1. This accuracy can potentially be improved with better survey photometric calibration. For the lower redshift sample, ~5 per cent of clusters show some (minor) contamination from secondary systems with the same red-sequence intruding into the measurement aperture of the original cluster. At z ~ 1, the rate rises to ~20 per cent. Approximately ten per cent of projections are expected to be serious, where the two components contribute significant numbers of their red-sequence galaxies to another cluster. Finally, we present a preliminary study of the mass-richness calibration using velocity dispersions to probe the dynamical masses of the clusters. We find a relation broadly consistent with that seen in the local universe from the WINGS sample at z ~ 0.05. © 2018 The Author(s). https://academic.oup.com/mnras/article/476/2/1991/4848316

Gravitationally lensed quasars are powerful and versatile astrophysical tools, but they are challengingly rare. In particular, only ~25 well-characterized quadruple systems are known to date. To refine the target catalogue for the forthcoming Taipan Galaxy Survey, the images of a large number of sources are being visually inspected in order to identify objects that are confused by a foreground star or galaxies that have a distinct multi-component structure. An unexpected by-product of this work has been the serendipitous discovery of about a dozen galaxies that appear to be lensing quasars, i.e. pairs or quartets of foreground stellar objects in close proximity to the target source. Here we report two diamond-shaped systems. Follow-up spectroscopy with the IMACS instrument on the 6.5m Magellan Baade telescope confirms one of these as a z = 1.975 quasar quadruply lensed by a double galaxy at z = 0.293. Photometry from publicly available survey images supports the conclusion that the other system is a highly sheared quadruply-imaged quasar. In starting with objects thought to be galaxies, our lens finding technique complements the conventional approach of first identifying sources with quasar-like colours and subsequently finding evidence of lensing., Comment: Accepted to MNRAS

We report the discovery, spectroscopic confirmation and first lens models of the first two, strongly lensed quasars from a combined search in WISE and Gaia over the DES footprint. The four-image lensWGD2038-4008 (r.a.=20:38:02.65, dec.=-40:08:14.64) has source- and lens-redshifts $z_{s}=0.777 \pm 0.001$ and $z_l = 0.230 \pm 0.002$ respectively. Its deflector has effective radius $R_{\rm eff} \approx 3.4^{\prime\prime}$, stellar mass $\log(M_{\star}/M_{\odot}) = 11.64^{+0.20}_{-0.43}$, and shows extended isophotal shape variation. Simple lens models yield Einstein radii $R_{\rm E}=(1.30\pm0.04)^{\prime\prime},$ axis ratio $q=0.75\pm0.1$ (compatible with that of the starlight) and considerable shear-ellipticity degeneracies. The two-image lensWGD2021-4115 (r.a.=20:21:39.45, dec.=--41:15:57.11) has $z_{s}=1.390\pm0.001$ and $z_l = 0.335 \pm 0.002$, and Einstein radius $R_{\rm E} = (1.1\pm0.1)^{\prime\prime},$ but higher-resolution imaging is needed to accurately separate the deflector and faint quasar image. We also show high-rank candidate doubles selected this way, some of which have been independently identified with different techniques, and discuss a DES+WISE quasar multiplet selection., Comment: MNRAS subm. 21/10/2017, awaiting reviewer selection. This paper has been approved by DES Collaboration-Wide Review

We present time-delay measurements for the new quadruple imaged quasar DES J0408-5354, the first quadruple imaged quasar found in the Dark Energy Survey (DES). Our result is made possible by implementing a new observational strategy using almost daily observations with the MPIA 2.2 m telescope at La Silla observatory and deep exposures reaching a signal-to-noise ratio of about 1000 per quasar image. This data qualityallows us to catch small photometric variations (a few mmag rms) of the quasar, acting on temporal scales much shorter than microlensing, and hence making the time delay measurement very robust against microlensing. In only seven months we very accurately measured one of the time delays in DES J0408-5354: ∆t(AB) = -112.1 ± 2.1 days (1.8%) using only the MPIA 2.2 m data. In combination with data taken with the 1.2 m Euler Swiss telescope, we also measured two delays involving the D component of the system ∆t(AD) = -155.5 ± 12.8 days (8.2%) and ∆t(BD) = -42.4 ± 17.6 days (41%), where all the error bars include systematics. Turning these time delays into cosmological constraints will require deep Hubble Space Telescope (HST) imaging or ground-based adaptive optics (AO), and information on the velocity field of the lensing galaxy. Lightcurves are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/609/A71

We report upon the follow up of 34 candidate lensed quasars found in the Dark Energy Survey using NTT-EFOSC, Magellan-IMACS, KECK-ESI and SOAR-SAMI. These candidates were selected by a combination of double component fitting, morphological assessment and color analysis. Most systems followed up are indeed composed of at least one quasar image and 13 with two or more quasar images: two lenses, four projected binaries and seven Nearly Identical Quasar Pairs (NIQs). The two systems confirmed as genuine gravitationally lensed quasars are one quadruple at zs=1.713 and one double at zs=1.515. Lens modeling of these two systems reveals that both systems require very little contribution from the environment to reproduce the image configuration. Nevertheless, small flux anomalies can be observed in one of the images of the quad. Further observations of 9 inconclusive systems (including 7 NIQs) will allow to confirm (or not) their gravitational lens nature., T. A. acknowledges support by proyecto FONDECYT 11130630 and by the Ministry for the Economy, Development, and Tourism's Programa Inicativa Científica Milenio through grant IC 12009, awarded to The Millennium Institute of Astrophysics (MAS). T.T. and V.M. acknowledge support by the Packard Foundation through a Packard Research Fellowship to T.T. T.T. acknowledges support by the National Science Foundation through grant AST-1450141. Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundacâo Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministerio da Ciência, Tecnologia e Inovacâo, the Deutsche Forschungsgemeinschaft and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas-Madrid, the University of Chicago, University College London, the DES Brazil Consortium, the University of Edinburgh, the Eidgen össische Technische Hochschule (ETH) Zürich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ciències de l'Espai (IEEC/CSIC), the Institut de Física d'Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig- Maximilians Universität München and the associated Excellence Cluster Universe, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, The Ohio State University, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, Texas A&M University, and the OzDES Membership Consortium

We report the discovery of a new gravitationally lensed quasar (double) from the Optical Gravitational Lensing Experiment (OGLE) identified inside the $\sim$670 sq. deg area encompassing the Magellanic Clouds. The source was selected as one of $\sim$60 "red W1-W2" mid-IR objects from WISE and having a significant amount of variability in OGLE for both two (or more) nearby sources. This is the first detection of a gravitational lens, where the discovery is made "the other way around", meaning we first measured the time delay between the two lensed quasar images of $-132, Comment: Accepted by MNRAS

[abridged] The Hubble and Spitzer Space Telescope surveys of the Frontier Fields (FF) provide extremely deep images around six massive, strong-lensing clusters of galaxies. The ALMA FF survey aims to cover the same fields at 1.1mm, with maps reaching (unlensed) sensitivities of $$5$\sigma$) sources in the first three FF clusters observed by ALMA, based on data from Hubble and Spitzer, the VLT and Herschel. We measure the total photometry in all available bands and determine the photometric redshifts and the physical properties of the counterparts via SED-fitting. In particular, we carefully estimate the FIR photometry using 1.1mm priors to limit the misidentification of blended FIR counterparts, which strongly affect some flux estimates in previous FIR catalogs. We identify robust near-infrared (NIR) counterparts for all 11 sources with K$_s$ detection, the majority of which are quite red, with eight having $F814W-K_s\gtrsim 4$ and five having $F160W-[4.5]\gtrsim3$. From the FIR point of view, all our objects have $z_{phot}$$\sim$1--3, whereas based on the optical SED one object prefers a high-$z$ solution ($z\geq\ $7). Five objects among our sample have spectroscopic redshifts from the GLASS survey for which we can reproduce their SEDs with existing templates. This verification confirms the validity of our photometric redshift methodology. The mean redshift of our sample is $z_{phot}$=1.99$\pm$0.27. All 1.1mm selected objects are massive (10.0$ \approx$1.6) and high dust contents (8.1 $, Comment: 18 pages, 11 figures, accepted for publication in A&A

We present V and R photometry of the gravitationally lensed quasars WFI2033-4723 and HE0047-1756. The data were taken by the MiNDSTEp collaboration with the 1.54 m Danish telescope at the ESO La Silla observatory from 2008 to 2012. Differential photometry has been carried out using the image subtraction method as implemented in the HOTPAnTS package, additionally using GALFIT for quasar photometry. The quasar WFI2033-4723 showed brightness variations of order 0.5 mag in V and R during the campaign. The two lensed components of quasar HE0047-1756 varied by 0.2-0.3 mag within five years. We provide, for the first time, an estimate of the time delay of component B with respect to A of $\Delta t= 7.6\pm1.8$ days for this object. We also find evidence for a secular evolution of the magnitude difference between components A and B in both filters, which we explain as due to a long-duration microlensing event. Finally we find that both quasars WFI2033-4723 and HE0047-1756 become bluer when brighter, which is consistent with previous studies., Comment: 16 pages, 15 figures, 10 tables. Accepted for publication in A&A

Gravitational microlensing is a powerful tool allowing one to probe the structure of quasars on sub-parsec scale. We report recent results, focusing on the broad absorption and emission line regions. In particular microlensing reveals the intrinsic absorption hidden in the P Cygni-type line profiles observed in the broad absorption line quasar H1413+117, as well as the existence of an extended continuum source. In addition, polarization microlensing provides constraints on the scattering region. In the quasar Q2237+030, microlensing differently distorts the H$\alpha$ and CIV broad emission line profiles, indicating that the low- and high-ionization broad emission lines must originate from regions with distinct kinematical properties. We also present simulations of the effect of microlensing on line profiles considering simple but representative models of the broad emission line region. Comparison of observations to simulations allows us to conclude that the H$\alpha$ emitting region in Q2237+030 is best represented by a Keplerian disk., Comment: in Proceedings of the conference "Quasars at all cosmic epochs", held in Padova, April 2-7, 2017; accepted for publication in Frontiers in Astronomy and Space Sciences, Research Topic "Quasars at all cosmic epochs"

We present the rationale for and the observational description of ASPECS: The ALMA SPECtroscopic Survey in the Hubble Ultra-Deep Field (UDF), the cosmological deep field that has the deepest multi-wavelength data available. Our overarching goal is to obtain an unbiased census of molecular gas and dust continuum emission in high-redshift (z$>$0.5) galaxies. The $\sim$1$'$ region covered within the UDF was chosen to overlap with the deepest available imaging from HST. Our ALMA observations consist of full frequency scans in band 3 (84-115 GHz) and band 6 (212-272 GHz) at approximately uniform line sensitivity ($L'_{\rm CO}\sim$2$\times$10$^{9}$ K km/s pc$^2$), and continuum noise levels of 3.8 $\mu$Jy beam$^{-1}$ and 12.7 $\mu$Jy beam$^{-1}$, respectively. The molecular surveys cover the different rotational transitions of the CO molecule, leading to essentially full redshift coverage. The [CII] emission line is also covered at redshifts $6.0, Comment: Submitted to the Astrophysical Journal, incorporating the first round of referee comments

In this paper we use ASPECS, the ALMA Spectroscopic Survey in the {\em Hubble} Ultra Deep Field (UDF) in band 3 and band 6, to place blind constraints on the CO luminosity function and the evolution of the cosmic molecular gas density as a function of redshift up to $z\sim 4.5$. This study is based on galaxies that have been solely selected through their CO emission and not through any other property. In all of the redshift bins the ASPECS measurements reach the predicted `knee' of the CO luminosity function (around $5\times10^{9}$ K km/s pc$^2$). We find clear evidence of an evolution in the CO luminosity function with respect to $z\sim 0$, with more CO luminous galaxies present at $z\sim 2$. The observed galaxies at $z\sim 2$ also appear more gas-rich than predicted by recent semi-analytical models. The comoving cosmic molecular gas density within galaxies as a function of redshift shows a factor 3-10 drop from $z \sim 2$ to $z \sim 0$ (with significant error bars), and possibly a decline at $z>3$. This trend is similar to the observed evolution of the cosmic star formation rate density. The latter therefore appears to be at least partly driven by the increased availability of molecular gas reservoirs at the peak of cosmic star formation ($z\sim2$)., Accepted for publication in the Astrophysical Journal

Aims: We present and study spatially resolved imaging obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) of multiple $^{12}$CO($J=$6$-$5, 8$-$7 and 9$-$8) and two H$_2$O(2$_{02}-$1$_{11}$ and 2$_{11}-$2$_{02}$) emission lines and cold dust continuum toward the gravitationally lensed dusty star forming galaxy SPT0346-52 at z=$5.656$. Methods: Using a visibility-domain source-plane reconstruction we probe the structure and dynamics of the different components of the interstellar medium (ISM) in this galaxy down to scales of 1 kpc in the source plane. Results: Measurements of the intrinsic sizes of the different CO emission lines indicate that the higher J transitions trace more compact regions in the galaxy. Similarly, we find smaller dust continuum intrinsic sizes with decreasing wavelength, based on observations at rest-frame 130, 300 and 450$\mu$m. The source shows significant velocity structure, and clear asymmetry where an elongated structure is observed in the source plane with significant variations in their reconstructed sizes. This could be attributed to a compact merger or turbulent disk rotation. The differences in velocity structure through the different line tracers, however, hint at the former scenario in agreement with previous [CII] line imaging results. Measurements of the CO line ratios and magnifications yield significant variations as a function of velocity, suggesting that modeling of the ISM using integrated values could be misinterpreted. Modeling of the ISM in SPT0346-52 based on delensed fluxes indicate a highly dense and warm medium, qualitatively similar to that observed in high redshift quasar hosts., Comment: 13 pages, 10 figures, accepted for publication in Astronomy and Astrophysics

[abridged] Characterizing the number counts of faint, dusty star-forming galaxies is currently a challenge even for deep, high-resolution observations in the FIR-to-mm regime. They are predicted to account for approximately half of the total extragalactic background light at those wavelengths. Searching for dusty star-forming galaxies behind massive galaxy clusters benefits from strong lensing, enhancing their measured emission while increasing spatial resolution. Derived number counts depend, however, on mass reconstruction models that properly constrain these clusters. We estimate the 1.1 mm number counts along the line of sight of three galaxy clusters, i.e. Abell 2744, MACSJ0416.1-2403 and MACSJ1149.5+2223, which are part of the ALMA Frontier Fields Survey. We perform detailed simulations to correct these counts for lensing effects. We use several publicly available lensing models for the galaxy clusters to derive the intrinsic flux densities of our sources. We perform Monte Carlo simulations of the number counts for a detailed treatment of the uncertainties in the magnifications and adopted source redshifts. We find an overall agreement among the number counts derived for the different lens models, despite their systematic variations regarding source magnifications and effective areas. Our number counts span ~2.5 dex in demagnified flux density, from several mJy down to tens of uJy. Our number counts are consistent with recent estimates from deep ALMA observations at a 3$\sigma$ level. Below $\approx$ 0.1 mJy, however, our cumulative counts are lower by $\approx$ 1 dex, suggesting a flattening in the number counts. In our deepest ALMA mosaic, we estimate number counts for intrinsic flux densities $\approx$ 4 times fainter than the rms level. This highlights the potential of probing the sub-10 uJy population in larger samples of galaxy cluster fields with deeper ALMA observations., Comment: 19 pages, 14 figures, 3 tables. Accepted for publication in A&A

Dusty star-forming galaxies are among the most prodigious systems at high redshift (z>1), characterized by high star formation rates and huge dust reservoirs. The bright end of this population has been well characterized in recent years, but considerable uncertainties remain for fainter dusty star-forming galaxies, which are responsible for the bulk of star formation at high redshift and thus play a key role in galaxy growth and evolution. In this first paper of our series, we describe our methods for finding high redshift faint dusty galaxies using millimeter observations with ALMA. We obtained ALMA 1.1 mm mosaic images for three strong-lensing galaxy clusters from the Frontier Fields survey. The 2'x2' mosaics overlap with the deep HST WFC3/IR footprints and encompass the high magnification regions of each cluster. The combination of extremely high ALMA sensitivity and the magnification power of these clusters allows us to systematically probe the sub-mJy population of dusty star-forming galaxies over a large surveyed area. We present a description of the reduction and analysis of the ALMA continuum observations for the galaxy clusters Abell 2744 (z=0.308), MACSJ0416.1-2403 (z=0.396) and MACSJ1149.5+2223 (z=0.543), for which we reach observed rms sensitivities of 55, 59 and 71 $��$Jy beam$^{-1}$ respectively. We detect 12 dusty star-forming galaxies at S/N>5.0 across the three clusters, all of them presenting coincidence with NIR detected counterparts in the HST images. None of the sources fall close to the lensing caustics, thus they are not strongly lensed. The observed 1.1 mm flux densities for the total sample of galaxies range from 0.41 to 2.82 mJy, with observed effective radii spanning, Accepted for publication in A&A. New version addressing last referee comments, 17 pages and 12 figures

We present an analysis of a deep (1$\sigma$=13 $\mu$Jy) cosmological 1.2-mm continuum map based on ASPECS, the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field. In the 1 arcmin$^2$ covered by ASPECS we detect nine sources at $>3.5\sigma$ significance at 1.2-mm. Our ALMA--selected sample has a median redshift of $z=1.6\pm0.4$, with only one galaxy detected at z$>$2 within the survey area. This value is significantly lower than that found in millimeter samples selected at a higher flux density cut-off and similar frequencies. Most galaxies have specific star formation rates similar to that of main sequence galaxies at the same epoch, and we find median values of stellar mass and star formation rates of $4.0\times10^{10}\ M_\odot$ and $\sim40~M_\odot$ yr$^{-1}$, respectively. Using the dust emission as a tracer for the ISM mass, we derive depletion times that are typically longer than 300 Myr, and we find molecular gas fractions ranging from $\sim$0.1 to 1.0. As noted by previous studies, these values are lower than using CO--based ISM estimates by a factor $\sim$2. The 1\,mm number counts (corrected for fidelity and completeness) are in agreement with previous studies that were typically restricted to brighter sources. With our individual detections only, we recover $55\pm4\%$ of the extragalactic background light (EBL) at 1.2 mm measured by the Planck satellite, and we recover $80\pm7\%$ of this EBL if we include the bright end of the number counts and additional detections from stacking. The stacked contribution is dominated by galaxies at $z\sim1-2$, with stellar masses of (1-3)$\times$10$^{10}$ M$_\odot$. For the first time, we are able to characterize the population of galaxies that dominate the EBL at 1.2 mm., Comment: Accepted for publication on the Astrophysical Journal

The microlensing event OGLE-2008-BLG-510 is characterised by an evident asymmetric shape of the peak, promptly detected by the ARTEMiS system in real time. The skewness of the light curve appears to be compatible both with binary-lens and binary-source models, including the possibility that the lens system consists of an M dwarf orbited by a brown dwarf. The detection of this microlensing anomaly and our analysis demonstrates that: 1) automated real-time detection of weak microlensing anomalies with immediate feedback is feasible, efficient, and sensitive, 2) rather common weak features intrinsically come with ambiguities that are not easily resolved from photometric light curves, 3) a modelling approach that finds all features of parameter space rather than just the `favourite model' is required, and 4) the data quality is most crucial, where systematics can be confused with real features, in particular small higher-order effects such as orbital motion signatures. It moreover becomes apparent that events with weak signatures are a silver mine for statistical studies, although not easy to exploit. Clues about the apparent paucity of both brown-dwarf companions and binary-source microlensing events might hide here.

We report the quadruple nature of the source WISE 025942.9-163543 as observed in the VST-ATLAS survey. Spectra of the two brightest images show quasar emission lines at z=2.16. The system was discovered by splitting ATLAS "cutouts" of WISE sources with W1-W2 > 0.7, when possible, into three components. Followup Magellan images were used to obtain astrometry and g and i photometry, with i=18.78 and 19.73, respectively, for the brightest and faintest components. Absorption lines are observed at z=0.905 but there is little evidence for a lensing galaxy after PSF fitting and subtraction. Saha and Williams (2003) would classify ATLAS 0259-1635 as a short-axis quad. The larger and smaller diameters are 1.57 and 1.32 arcseconds, respectively. Modeling the lensing galaxy as a singular isothermal sphere with external shear, the largest and smallest predicted magnifications are 10.8 and 6.4 respectively., 3 pages, 1 figure

We use the high magnification event seen in the 1999 OGLE campaign light curve of image C of the quadruply imaged gravitational lens Q2237+0305 to study the structure of the quasar engine. We have obtained g'- and r'-band photometry at the Apache Point Observatory 3.5m telescope where we find that the event has a smaller amplitude in the r'-band than in the g'- and OGLE V-bands. By comparing the light curves with microlensing simulations we obtain constraints on the sizes of the quasar regions contributing to the g'- and r'-band flux. Assuming that most of the surface mass density in the central kiloparsec of the lensing galaxy is due to stars and by modeling the source with a Gaussian profile, we obtain for the Gaussian width 1.20 x 10^15 sqrt(M/0.1M_sun)cm < sigma_g' < 7.96 x 10^15 sqrt(M/0.1Msun) cm, where M is the mean microlensing mass, and a ratio sigma_r'/sigma_g'=1.25^{+0.45}_{-0.15}. With the limits on the velocity of the lensing galaxy from Gil-Merino et al. (2005) as our only prior, we obtain 0.60 x 10^15 sqrt(M/0.1Msun) cm < sigma_g' < 1.57 x 10^15 sqrt(M/0.1Msun) cm and a ratio sigma_r'/sigma_g'=1.45^{+0.90}_{-0.25} (all values at 68 percent confidence). Additionally, from our microlensing simulations we find that, during the chromatic microlensing event observed, the continuum emitting region of the quasar crossed a caustic at >72 percent confidence., Accepted for publication in A&A, 8 pages, 4 figures. Slightly modified compared to the original version: qualitative results unchanged, constraints on the r'/g' source size ratio now tighter due to correction of an error in the numerical treatment of the simulated light curves

We present an extensive spectroscopic follow-up campaign of 29 strong lensing (SL) selected galaxy clusters discovered primarily in the Second Red-Sequence Cluster Survey (RCS-2). Our spectroscopic analysis yields redshifts for 52 gravitational arcs present in the core of our galaxy clusters, which correspond to 35 distinct background sources that are clearly distorted by the gravitational potential of these clusters. These lensed galaxies span a wide redshift range of $0.8 \le z \le 2.9$, with a median redshift of $z_s = 1.8 \pm 0.1 $. We also measure reliable redshifts for 1004 cluster members, allowing us to obtain robust velocity dispersion measurements for 23 of these clusters, which we then use to determine their dynamical masses by using a simulation-based $\sigma_{DM} - M_{200}$ scaling relation. The redshift and mass ranges covered by our SL sample are $0.22 \le z \le 1.01$ and $5 \times10^{13} \le M_{200}/h^{-1}_{70}M_{\odot} \le 1.9\times10^{15}$, respectively. We analyze and quantify some possible effects that might bias our mass estimates, such as the presence of substructure, the region where cluster members are selected for spectroscopic follow-up, the final number of confirmed members, and line-of-sight effects. We find that 10 clusters of our sample with $N_{mem} \gtrsim 20$ show signs of dynamical substructure. However, the velocity data of only one system is inconsistent with a uni-modal distribution. We therefore assume that the substructures are only marginal and not of comparable size to the clusters themselves. Consequently, our velocity dispersion and mass estimates can be used as priors for SL mass reconstruction studies and also represent an important step toward a better understanding of the properties of the SL galaxy cluster population., Comment: Accepted for publication in ApJ

BOMBOLO is a new multi-passband visitor instrument for the SOAR observatory. It is a three-arm imager covering the near-UV and optical wavelengths. The three arms work simultaneously and independently, providing synchronized imaging capability for rapid astronomical events. BOMBOLO leading science cases are: 1) Simultaneous Multiband Flickering Studies of Accretion Phenomena; 2) Near UV/Optical Diagnostics of Stellar Evolutionary Phases; 3) Exoplanetary Transits; 4) Microlensing Follow-Up and 5) Solar Systems Studies. The instrument is at the Conceptual Design stage, having been approved by the SOAR Board of Directors as a visitor instrument in 2012 and having been granted full funding from CONICYT, the Chilean State Agency of Research, in 2013. The Design Phase has begun and will be completed in late 2014, followed by a construction phase in 2015 and 2016A, with expected Commissioning in 2016B and 2017A.

Aims. Construction of a new quasar candidate catalog from the Red-Sequence Cluster Survey 2 (RCS-2), identified solely from photometric information using an automated algorithm suitable for large surveys. The algorithm performance is tested using a well-defined SDSS spectroscopic sample of quasars and stars. Methods. The Random Forest algorithm constructs the catalog from RCS-2 point sources using SDSS spectroscopically-confirmed stars and quasars. The algorithm identifies putative quasars from broadband magnitudes (g, r, i, z) and colours. Exploiting NUV GALEX measurements for a subset of the objects, we refine the classifier by adding new information. An additional subset of the data with WISE W1 and W2 bands is also studied. Results. Upon analyzing 542,897 RCS-2 point sources, the algorithm identified 21,501 quasar candidates, with a training-set-derived precision (the fraction of true positives within the group assigned quasar status) of 89.5% and recall (the fraction of true positives relative to all sources that actually are quasars) of 88.4%. These performance metrics improve for the GALEX subset; 6,530 quasar candidates are identified from 16,898 sources, with a precision and recall respectively of 97.0% and 97.5%. Algorithm performance is further improved when WISE data are included, with precision and recall increasing to 99.3% and 99.1% respectively for 21,834 quasar candidates from 242,902 sources. We compile our final catalog (38,257) by merging these samples and removing duplicates. An observational follow up of 17 bright (r < 19) candidates with long-slit spectroscopy at DuPont telescope (LCO) yields 14 confirmed quasars. Conclusions. The results signal encouraging progress in the classification of point sources with Random Forest algorithms to search for quasars within current and future large-area photometric surveys., Accepted for publication in A&A. 20 pages, 16 figures, 6 tables. Tables 1, 2 and 3 with the quasar candidates are only available in electronic format http://www.aanda.org/

Using infrared spectra of the z = 1.693 quadruply lensed quasar HE0435-1223 acquired in 2009 with the spectrograph SINFONI at the ESO Very Large Telescope, we have detected a clear microlensing effect in images A and D. While microlensing affects the blue and red wings of the H{\alpha} line profile in image D very differently, it de-magnifies the line core in image A. The combination of these different effects sets constraints on the line-emitting region; these constraints suggest that a rotating ring is at the origin of the H{\alpha} line. Visible spectra obtained in 2004 and 2012 indicate that the MgII line profile is microlensed in the same way as the H{\alpha} line. Our results therefore favour flattened geometries for the low-ionization line-emitting region, for example, a Keplerian disk. Biconical models cannot be ruled out but require more fine-tuning. Flux ratios between the different images are also derived and confirm flux anomalies with respect to estimates from lens models with smooth mass distributions., Comment: 6 pages, 4 figures, 3 tables, accepted by A&A on 10 April 2014

We present a search for [C II] line and dust continuum emission from optical dropout galaxies at z > 6 using ASPECS, our Atacama Large Millimeter submillimeter Array Spectroscopic Survey in the Hubble Ultra-deep Field (UDF). Our observations, which cover the frequency range of 212–272 GHz, encompass approximately the range of 6 4.5σ, two of which correspond to blind detections with no optical counterparts. At this significance level, our statistical analysis shows that about 60% of our candidates are expected to be spurious. For one of our blindly selected [C II] line candidates, we tentatively detect the CO(6-5) line in our parallel 3 mm line scan. None of the line candidates are individually detected in the 1.2 mm continuum. A stack of all [C II] candidates results in a tentative detection with S_(1.2 mm) = 14 ± 5 μJy. This implies a dust-obscured star-formation rate (SFR) of (3 ± 1) M⊙ yr^(-1). We find that the two highest-SFR objects have candidate [C II] lines with luminosities that are consistent with the low-redshift L_([C II]) versus SFR relation. The other candidates have significantly higher [C II] luminosities than expected from their UV-based SFR. At the current sensitivity, it is unclear whether the majority of these sources are intrinsically bright [C II] emitters, or spurious sources. If only one of our line candidates was real (a scenario greatly favored by our statistical analysis), we find a source density for [C II] emitters at 6 < z < 8 that is significantly higher than predicted by current models and some extrapolations from galaxies in the local universe.

Multiply-imaged quasars and AGNs observed in the mid-infrared (MIR) range are commonly assumed to be unaffected by the microlensing produced by the stars in their lensing galaxy. In this paper, we investigate the validity domain of this assumption. Indeed, that premise disregards microlensing of the accretion disc in the MIR range, and does not account for recent progress in our knowledge of the dusty torus. To simulate microlensing, we first built a simplified image of the quasar composed of an accretion disc, and of a larger ring-like torus. The mock quasars are then microlensed using an inverse ray-shooting code. We simulated the wavelength and size dependence of microlensing for different lensed image types and fraction of compact objects projected in the lens. This allows us to derive magnification probabilities as a function of wavelength, as well as to calculate the microlensing-induced deformation of the spectral energy distribution of the lensed images. We find that microlensing variations as large as 0.1 mag are very common at 11 microns (observer-frame). The main signal comes from microlensing of the accretion disc, which may be significant even when the fraction of flux from the disc is as small as 5 % of the total flux. We also show that the torus of sources with Lbol, Comment: Updated to match the version published in Astronomy and Astrophysics. 12 pages. Abridged version of the abstract. Microlensing maps and source profiles used in the simulations are available via CDS - http://vizier.cfa.harvard.edu/viz-bin/VizieR?-source=J/A+A/553/A53

With the aim of characterizing the flux and color variations of the multiple components of the gravitationally lensed quasar UM673 as a function of time, we have performed multi-epoch and multi-band photometric observations with the Danish 1.54m telescope at the La Silla Observatory. The observations were carried out in the VRi spectral bands during four seasons (2008--2011). We reduced the data using the PSF (Point Spread Function) photometric technique as well as aperture photometry. Our results show for the brightest lensed component some significant decrease in flux between the first two seasons (+0.09/+0.11/+0.05 mag) and a subsequent increase during the following ones (-0.11/-0.11/-0.10 mag) in the V/R/i spectral bands, respectively. Comparing our results with previous studies, we find smaller color variations between these seasons as compared with previous ones. We also separate the contribution of the lensing galaxy from that of the fainter and close lensed component., 7 pages, 8 figures, 4 tables

We investigate the kinematics and ionization structure of the broad emission line region of the gravitationally lensed quasar QSO2237+0305 (the Einstein cross) using differential microlensing in the high- and low-ionization broad emission lines. We combine visible and near-infrared spectra of the four images of the lensed quasar and detect a large-amplitude microlensing effect distorting the high-ionization CIV and low-ionization H$\alpha$ line profiles in image A. While microlensing only magnifies the red wing of the Balmer line, it symmetrically magnifies the wings of the CIV emission line. Given that the same microlensing pattern magnifies both the high- and low-ionization broad emission line regions, these dissimilar distortions of the line profiles suggest that the high- and low-ionization regions are governed by different kinematics. Since this quasar is likely viewed at intermediate inclination, we argue that the differential magnification of the blue and red wings of H$\alpha$ favors a flattened, virialized, low-ionization region whereas the symmetric microlensing effect measured in CIV can be reproduced by an emission line formed in a polar wind, without the need of fine-tuned caustic configurations., Comment: 11 pages, 4 figures, A&A

We precisely constrain the inner mass profile of Abell 2261 (z=0.225) for the first time and determine this cluster is not "over-concentrated" as found previously, implying a formation time in agreement with {\Lambda}CDM expectations. These results are based on strong lensing analyses of new 16-band HST imaging obtained as part of the Cluster Lensing and Supernova survey with Hubble (CLASH). Combining this with revised weak lensing analyses of Subaru wide field imaging with 5-band Subaru + KPNO photometry, we place tight new constraints on the halo virial mass M_vir = 2.2\pm0.2\times10^15 M\odot/h70 (within r \approx 3 Mpc/h70) and concentration c = 6.2 \pm 0.3 when assuming a spherical halo. This agrees broadly with average c(M,z) predictions from recent {\Lambda}CDM simulations which span 5

We have obtained spectropolarimetric observations of the four images of the gravitationally lensed broad absorption line quasar H1413+117. The polarization of the microlensed image D is significantly different both in the continuum and in the broad lines from the polarization of image A which is essentially unaffected by microlensing. The observations suggest that the continuum is scattered off two regions spatially separated and producing roughly perpendicular polarizations. These results are compatible with a model in which the microlensed polarized continuum comes from a compact region located in the equatorial plane close to the accretion disk and the non-microlensed continuum from an extended region located along the polar axis., Comment: Accepted for publication in Astronomy and Astrophysics; minor changes (language editing)

Testing the standard Shakura-Sunyaev model of accretion is a challenging task because the central region of quasars where accretion takes place is unresolved with telescopes. The analysis of microlensing in gravitationally lensed quasars is one of the few techniques that can test this model, yielding to the measurement of the size and of temperature profile of the accretion disc. We present spectroscopic observations of the gravitationally lensed broad absorption line quasar H1413+117, which reveal partial microlensing of the continuum emission that appears to originate from two separated regions: a microlensed region, corresponding to the compact accretion disc; and a non-microlensed region, more extended and contributing to at least 30\% of the total UV-continuum flux. Because this extended continuum is occulted by the broad absorption line clouds, it is not associated with the host galaxy, but rather with light scattered in the neighbourhood of the central engine. We measure the amplitude of microlensing of the compact continuum over the rest-frame wavelength range 1000-7000 \AA. Following a Bayesian scheme, we confront our measurements to microlensing simulations of an accretion disc with a temperature varying as $T \propto R^{-1/\nu}$. We find a most likely source half-light radius of $R_{1/2} = 0.61 \times 10^{16}\,$cm (i.e., 0.002\,pc) at 0.18\,$\mu$m, and a most-likely index of $\nu=0.4$. The standard disc ($\nu=4/3$) model is not ruled out by our data, and is found within the 95\% confidence interval associated with our measurements. We demonstrate that, for H1413+117, the existence of an extended continuum in addition to the disc emission only has a small impact on the inferred disc parameters, and is unlikely to solve the tension between the microlensing source size and standard disc sizes, as previously reported in the literature., Comment: Accepted for publication in Astronomy and Astrophysics. 12 pages. Minor changes w.r.t. v1 (language editing, Fig. 5-6)

Among the 100 strong lens candidates found in the COSMOS field, 20 with redshifts in the range [0.34,1.13], feature multiple images of background sources. Using the multi-wavelength coverage of the field and its spectroscopic follow-up, we characterize the evolution with redshift of the environment and of the dark-matter (DM) fraction of the lens galaxies. We present new redshift of the strong lens candidates. The lens environment is characterized by the projected 10 closest galaxies around each lens and by the number of galaxies with a projected distance less than 1Mpc at the lens galaxy redshift. In both cases, we perform similar measurements on a control sample of twin non-lens early type galaxies (ETGs). In addition, we identify group members and field galaxies in the X-ray and optical catalogs of galaxy groups. From those catalogs, we measure the external shear contribution at the lens galaxy positions. The systems are then modeled using a SIE plus the external shear due to the groups. We observe that the average stellar mass of lens galaxies increases with z and that the environment of lens galaxies is compatible with that of the twins. During the lens modeling, we notice that, when let free, the external shear points in a direction which is the mean direction of the external shear due to groups and of the closest galaxy to the lens. We notice that the DM fraction of the lens galaxies within the Einstein radius decreases as the redshift increases. Given these, we conclude that, while the environment of lens galaxies is compatible with that of non-lens ETGS, their mass properties evolves significantly with redshift: it is still not clear whether this advocates in favor of a stronger lensing bias toward massive objects at high redshift or is simply representative of the high proportion of massive and high stellar density galaxies at high redshift., Accepted for publication in A&A. Significant modifications in the paper but similar conclusions

Gravitational microlensing is not only a successful tool for discovering distant exoplanets, but it also enables characterization of the lens and source stars involved in the lensing event. In high magnification events, the lens caustic may cross over the source disk, which allows a determination of the angular size of the source and additionally a measurement of its limb darkening. When such extended-source effects appear close to maximum magnification, the resulting light curve differs from the characteristic Paczynski point-source curve. The exact shape of the light curve close to the peak depends on the limb darkening of the source. Dense photometric coverage permits measurement of the respective limb-darkening coefficients. In the case of microlensing event OGLE 2008-BLG-290, the K giant source star reached a peak magnification of about 100. Thirteen different telescopes have covered this event in eight different photometric bands. Subsequent light-curve analysis yielded measurements of linear limb-darkening coefficients of the source in six photometric bands. The best-measured coefficients lead to an estimate of the source effective temperature of about 4700 +100-200 K. However, the photometric estimate from colour-magnitude diagrams favours a cooler temperature of 4200 +-100 K. As the limb-darkening measurements, at least in the CTIO/SMARTS2 V and I bands, are among the most accurate obtained, the above disagreement needs to be understood. A solution is proposed, which may apply to previous events where such a discrepancy also appeared., Astronomy & Astrophysics in press