- ID:
- ivo://CDS.VizieR/J/MNRAS/466/3088
- Title:
- Lensed and extended quasars
- Short Name:
- J/MNRAS/466/3088
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Wide-field photometric surveys enable searches of rare yet interesting objects, such as strongly lensed quasars or quasars with a bright host galaxy. Past searches for lensed quasars based on their optical and near-infrared properties have relied on photometric cuts and spectroscopic preselection (as in the Sloan Quasar Lens Search), or neural networks applied to photometric samples. These methods rely on cuts in morphology and colours, with the risk of losing many interesting objects due to scatter in their population properties, restrictive training sets, systematic uncertainties in catalogue-based magnitudes and survey-to-survey photometric variations. Here, we explore the performance of a Gaussian mixture model to separate point-like quasars, quasars with an extended host and strongly lensed quasars using grizpsf and model magnitudes and WISEW1, W2. The choice of optical magnitudes is due to their presence in all current and upcoming releases of wide-field surveys, whereas UV information is not always available. We then assess the contamination from blue galaxies and the role of additional features such as W3 magnitudes or psf-model terms as morphological information. As a demonstration, we conduct a search in a random 10 per cent of the SDSS footprint, and provide the catalogue of the 43 SDSS object with the highest 'lens' score in our selection that survive visual inspection, and are spectroscopically confirmed to host active nuclei. We inspect archival data and find images of 5/43 objects in the Hubble Legacy Archive, including two known lenses.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/616/A118
- Title:
- Lensed QSOs light curves & spectral monitoring
- Short Name:
- J/A+A/616/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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=20mag 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 quasars, and other objects, where about 50% of the non-GLQs were observed as part of a campaign to identify GLQ candidates. Most observations of GLQs correspond to an ongoing long-term macro-programme with 2-10m telescopes at the Roque de los Muchachos Observatory, and these data provide information on the distribution of dark matter at all scales. We outline some previous results from the database, and we additionally obtain new results for several GLQs that update the potential of the tool for astrophysical studies.
- ID:
- ivo://CDS.VizieR/J/ApJ/792/76
- Title:
- Lensed z~6-8 galaxies behind CLASH clusters
- Short Name:
- J/ApJ/792/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We utilize 16 band Hubble Space Telescope (HST) observations of 18 lensing clusters obtained as part of the Cluster Lensing And Supernova survey with Hubble (CLASH) Multi-Cycle Treasury program to search for z ~ 6-8 galaxies. We report the discovery of 204, 45, and 13 Lyman-break galaxy candidates at z ~ 6, z ~ 7, and z ~ 8, respectively, identified from purely photometric redshift selections. This large sample, representing nearly an order of magnitude increase in the number of magnified star-forming galaxies at z ~ 6-8 presented to date, is unique in that we have observations in four WFC3/UVIS UV, seven ACS/WFC optical, and all five WFC3/IR broadband filters, which enable very accurate photometric redshift selections. We construct detailed lensing models for 17 of the 18 clusters to estimate object magnifications and to identify two new multiply lensed z >~ 6 candidates. The median magnifications over the 17 clusters are 4, 4, and 5 for the z ~ 6, z ~ 7, and z ~ 8 samples, respectively, over an average area of 4.5 arcmin^2^ per cluster. We compare our observed number counts with expectations based on convolving "blank" field UV luminosity functions through our cluster lens models and find rough agreement down to ~27 mag, where we begin to suffer significant incompleteness. In all three redshift bins, we find a higher number density at brighter observed magnitudes than the field predictions, empirically demonstrating for the first time the enhanced efficiency of lensing clusters over field surveys. Our number counts also are in general agreement with the lensed expectations from the cluster models, especially at z ~ 6, where we have the best statistics.
- ID:
- ivo://CDS.VizieR/J/ApJ/868/129
- Title:
- Lensing analysis in Abell 370
- Short Name:
- J/ApJ/868/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new gravitational lens model of the Hubble Frontier Fields cluster Abell 370 (z=0.375) using imaging and spectroscopy from Hubble Space Telescope and ground-based spectroscopy. We combine constraints from a catalog of 909 weakly lensed galaxies and 39 multiply imaged sources comprised of 114 multiple images, including a system of multiply imaged candidates at z=7.84+/-0.02, to obtain a best-fit mass distribution using the cluster lens modeling code strong and weak lensing united. As the only analysis of A370 using strong and weak lensing constraints from Hubble Frontier Fields (HFF) data, our method provides an independent check of assumptions on the mass distribution used in other methods. Convergence, shear, and magnification maps are made publicly available through the HFF website (http://www.stsci.edu/hst/campaigns/frontier-fields). We find that the model we produce is similar to models produced by other groups, with some exceptions due to the differences in lensing code methodology. In an effort to study how our total projected mass distribution traces light, we measure the stellar mass density distribution using Spitzer/Infrared array camera imaging. Comparing our total mass density to our stellar mass density in a radius of 0.3Mpc, we find a mean projected stellar to total mass ratio of <f*>=0.011+/-0.003 (stat.) using the diet Salpeter initial mass function. This value is in general agreement with independent measurements of <f*> in clusters of similar total mass and redshift.
- ID:
- ivo://CDS.VizieR/J/ApJ/723/1678
- Title:
- LensPerfect A1689 analysis
- Short Name:
- J/ApJ/723/1678
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a strong lensing (SL) mass model of A1689 which resolves substructures an estimated 25kpc across within the central ~400kpc diameter. We achieve this resolution by perfectly reproducing the observed (strongly lensed) input positions of 168 multiple images of 55 knots residing within 135 images of 42 galaxies. Our model makes no assumptions about light tracing mass, yet we reproduce the brightest visible structures with some slight deviations. A1689 remains one of the strongest known lenses on the sky, with an Einstein radius of R_E_=47.0+/-1.2" (143^+3^_-4_kpc) for a lensed source at z_s_=2. We find that a single Navarro-Frenk-White (NFW) or Sersic profile yields a good fit simultaneously (with only slight tension) to both our SL mass model and published weak lensing (WL) measurements at larger radius (out to the virial radius). Our SL model prefers slightly higher concentrations than previous SL models, bringing our SL+WL constraints in line with other recent derivations. Our results support those of previous studies which find A1689 has either an anomalously large concentration or significant extra mass along the line of sight (perhaps in part due to triaxiality).
- ID:
- ivo://CDS.VizieR/J/MNRAS/504/3662
- Title:
- Lya-UV Offsets in Galaxies at z~6
- Short Name:
- J/MNRAS/504/3662
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We study the projected spatial offset between the ultraviolet continuum and Lya emission for 65 lensed and unlensed galaxies in the Epoch of Reionization 5<=z<=7, the first such study at these redshifts, in order to understand the potential for these offsets to confuse estimates of the Lya properties of galaxies observed in slit spectroscopy. While we find that ~40% of galaxies in our sample show significant projected spatial offsets, |Delta_Lya-UV_|, we find a relatively modest average (median) projected offset of |Delta_Lya-UV_|=0.61+/-0.08 proper kpc for the entire sample. A small fraction of our sample, ~10%, exhibit offsets in excess of 2 proper kpc, with offsets seen up to ~4 proper kpc, sizes that are considerably larger than the effective radii of typical galaxies at these redshifts. An internal comparison and a comparison to studies at lower redshift yielded no significant evidence of evolution of Delta_Lya-UV with redshift. In our sample, UV-bright galaxies (with a median L_UV_/L*_UV_=0.67) showed offsets a factor of three greater than their fainter counterparts (median L_UV_/L*_UV_=0.10), 0.89 +/-0.18 vs. 0.27+/-0.05 proper kpc, respectively. The presence of companion galaxies and early-stage merging activity appeared to be unlikely causes of these offsets. Rather, these offsets appear consistent with a scenario in which internal anisotropic processes resulting from stellar feedback, which is stronger in UV-brighter galaxies, facilitate Lya fluorescence and/or backscattering from nearby or outflowing gas. The reduction in the Lya flux due to offsets was quantified. It was found that the differential loss of Lya photons for galaxies with average offsets is not, if corrected for, a limiting factor for all but the narrowest slit widths (<0.4"). However, for the largest offsets, if they are mostly perpendicular to the slit major axis, slit losses were found to be extremely severe in cases where slit widths of <=1" were employed, such as those planned for James Webb Space Telescope/NIRSpec observations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/443/1549
- Title:
- MACSJ0416.1-2403 strong-lensing analysis
- Short Name:
- J/MNRAS/443/1549
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high-precision mass model of the galaxy cluster MACSJ0416.1-2403, based on a strong-gravitational-lensing analysis of the recently acquired Hubble Space Telescope Frontier Fields (HFF) imaging data. Taking advantage of the unprecedented depth provided by HST/Advanced Camera for Survey observations in three passbands, we identify 51 new multiply imaged galaxies, quadrupling the previous census and bringing the grand total to 68, comprising 194 individual lensed images. Having selected a subset of the 57 most securely identified multiply imaged galaxies, we use the lenstool software package to constrain a lens model comprised of two cluster-scale dark-matter haloes and 98 galaxy-scale haloes. Our best-fitting model predicts image positions with an rms error of 0.68-arcsec, which constitutes an improvement of almost a factor of 2 over previous, pre-HFF models of this cluster. We find the total projected mass inside a 200kpc aperture to be (1.60+/-0.01)x10^14^M_{sun}_, a measurement that offers a three-fold improvement in precision, reaching the per cent level for the first time in any cluster. Finally, we quantify the increase in precision of the derived gravitational magnification of high-redshift galaxies and find an improvement by a factor of ~2.5 in the statistical uncertainty. Our findings impressively confirm that HFF imaging has indeed opened the domain of high-precision mass measurements for massive clusters of galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/404/325
- Title:
- Massive galaxy clusters lensing analyse
- Short Name:
- J/MNRAS/404/325
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a statistical analysis of a sample of 20 strong lensing clusters drawn from the Local Cluster Substructure Survey, based on high-resolution Hubble Space Telescope imaging of the cluster cores and follow-up spectroscopic observations using the Keck-I telescope.
- ID:
- ivo://CDS.VizieR/J/AJ/155/104
- Title:
- MEGaSaURA. I. The sample and the spectra
- Short Name:
- J/AJ/155/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We introduce Project MEGaSaURA: the Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas. MEGaSaURA comprises medium-resolution, rest-frame ultraviolet spectroscopy of N=15 bright gravitationally lensed galaxies at redshifts of 1.68<z<3.6, obtained with the MagE spectrograph on the Magellan telescopes. The spectra cover the observed-frame wavelength range 3200<{lambda}_o_<8280{AA}; the average spectral resolving power is R=3300. The median spectrum has a signal-to- noise ratio (S/N)=21 per resolution element at 5000{AA}. As such, the MEGaSaURA spectra have superior S/N and wavelength coverage compared to what COS/HST provides for starburst galaxies in the local universe. This paper describes the sample, the observations, and the data reduction. We compare the measured redshifts for the stars, the ionized gas as traced by nebular lines, and the neutral gas as traced by absorption lines; we find the expected bulk outflow of the neutral gas, and no systemic offset between the redshifts measured from nebular lines and the redshifts measured from the stellar continuum.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A108
- Title:
- MG B2016+112 radio images
- Short Name:
- J/A+A/630/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we exploit the gravitational lensing effect to detect proper motion in the highly magnified gravitationally lensed source MG B2016+112. We find positional shifts up to 6mas in the lensed images by comparing two very long baseline interferometric (VLBI) radio observations at 1.7GHz that are separated by 14.359 years, and provide an astrometric accuracy of the order of tens of as. From lens modelling, we exclude a shift in the lensing galaxy as the cause of the positional change of the lensed images, and we assign it to the background source. The source consists of four sub-components, separated by 175 pc, with proper motion of the order of tens {mu}as/yr for the two components at highest magnification ({mu}~350) and of the order of a few mas/yr for the two components at lower magnification ({mu}~2). We propose single Active Galactic Nuclei (AGN) and dual AGN scenarios to explain the source plane. Although, the latter interpretation is supported by the archival multi-wavelength properties of the object. In this case, MG B2016+112 would represent the highest redshift dual radio-loud AGN system discovered thus far, and would support the merger interpretation for such systems. Also, given the low probability (~10^-5^) of detecting a dual AGN system that is also gravitationally lensed, if confirmed, this would suggest that such dual AGN systems must be more abundant in the early Universe than currently thought.
