Three quasi-stellar objects acting as strong gravitational lenses

Courbin, F.; Fauré, C.; Djorgovski, S. G.; Rérat, F.; Tewes, M.; Meylan, G.; Stern, Daniel; Mahabal, A.; Boroson, Todd A.; Dheeraj, R Pasham; Sluse, Dominique

doi:10.1051/0004-6361/201118015

Cited by 23 publications

(19 citation statements)

References 28 publications

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“…Note that one result of this measurement is the fact that the mass range of host halos is significantly more extended in the exponential case than the lightbulb case. Thus, one way to break the degeneracy between the lightbulb and exponential models would be to measure the mass range of underlying host halos, perhaps through using gravitational lensing to independently find the mass of the dark matter halo (Courbin et al 2012). If the range of masses for quasar hosts is extended, then there would be observational evidence favoring an exponential model (or a model with evolution in the quasar light curve) as opposed to the lightbulb model.…”

Section: Mass Function and Duty Cycle Of Halo Hostsmentioning

confidence: 99%

Helium Reionization Simulations. I. Modeling Quasars as Radiation Sources

Plante

Trac

2016

ApJ

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We introduce a new project to understand helium reionization using fully coupled N -body, hydrodynamics, and radiative transfer simulations. This project aims to capture correctly the thermal history of the intergalactic medium (IGM) as a result of reionization and make predictions about the Lyman-α forest and baryon temperature-density relation. The dominant sources of radiation for this transition are quasars, so modeling the source population accurately is very important for making reliable predictions. In this first paper, we present a new method for populating dark matter halos with quasars. Our set of quasar models includes two different light curves, a lightbulb (simple on/off) and symmetric exponential model, and luminosity-dependent quasar lifetimes. Our method self-consistently reproduces an input quasar luminosity function given a halo catalog from an N -body simulation, and propagates quasars through the merger history of halo hosts. After calibrating quasar clustering using measurements from the Baryon Oscillation Spectroscopic Survey, we find that the characteristic mass of quasar hosts is M h ∼ 2.5 × 10 12 h −1 M for the lightbulb model, and M h ∼ 2.3 × 10 12 h −1 M for the exponential model. In the latter model, the peak quasar luminosity for a given halo mass is larger than that in the former model, typically by a factor of 1.5-2. The effective lifetime for quasars in the lightbulb model is 59 Myr, and in the exponential case, the effective time constant is about 15 Myr. We include semi-analytic calculations of helium reionization, and discuss how to include these quasars as sources of ionizing radiation for full hydrodynamics with radiative transfer simulations in order to study helium reionization.

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Section: Mass Function and Duty Cycle Of Halo Hostsmentioning

confidence: 99%

Helium Reionization Simulations. I. Modeling Quasars as Radiation Sources

Plante

Trac

2016

ApJ

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“…This has already been used to find lensed sources from PCA decomposition of quasar spectra (e.g. Courbin et al 2012;Boroson & Lauer 2010). We now adopt a similar strategy to analyse images.…”

Section: Principle Of the Algorithmmentioning

confidence: 99%

A PCA-based automated finder for galaxy-scale strong lenses

Joseph

Courbin

Metcalf

et al. 2014

A&A

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We present an algorithm using principal component analysis (PCA) to subtract galaxies from imaging data and also two algorithms to find strong, galaxy-scale gravitational lenses in the resulting residual image. The combined method is optimised to find full or partial Einstein rings. Starting from a pre-selection of potential massive galaxies, we first perform a PCA to build a set of basis vectors. The galaxy images are reconstructed using the PCA basis and subtracted from the data. We then filter the residual image with two different methods. The first uses a curvelet (curved wavelets) filter of the residual images to enhance any curved/ring feature. The resulting image is transformed in polar coordinates, centred on the lens galaxy. In these coordinates, a ring is turned into a line, allowing us to detect very faint rings by taking advantage of the integrated signal-to-noise in the ring (a line in polar coordinates). The second way of analysing the PCA-subtracted images identifies structures in the residual images and assesses whether they are lensed images according to their orientation, multiplicity, and elongation. We applied the two methods to a sample of simulated Einstein rings as they would be observed with the ESA Euclid satellite in the VIS band. The polar coordinate transform allowed us to reach a completeness of 90% for a purity of 86%, as soon as the signal-to-noise integrated in the ring was higher than 30 and almost independent of the size of the Einstein ring. Finally, we show with real data that our PCA-based galaxy subtraction scheme performs better than traditional subtraction based on model fitting to the data. Our algorithm can be developed and improved further using machine learning and dictionary learning methods, which would extend the capabilities of the method to more complex and diverse galaxy shapes.

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“…We now discuss the number of candidates obtained through our search across all SDSS-III QSOs, and compare it to the only previous search for such lenses. We first draw some parallels and differences between Courbin et al (2012) first 3 confirmed QSO-galaxy lenses and our 9 candidates. The two candidates samples do not overlap because we did not apply our algorithm to SDSS-I/-II.Indeed, our automated method is built around the PCA template for quasars which was introduced in SDSS-III.…”

Section: Number Of Qso-elg Systemsmentioning

confidence: 92%

“…Last but not least, the QSO outshines the lensed background source. This prevents the confirmation of the lensing systems with wide-field photometric data and highlights the crucial importance of high-resolution imaging to confirm such lenses (Courbin et al 2010(Courbin et al , 2012.…”

Section: Mining Boss For Candidate Qso Lensesmentioning

confidence: 99%

Quasi-stellar objects acting as potential strong gravitational lenses in the SDSS-III BOSS survey

Meyer

Delubac

Kneib

et al. 2019

A&A

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We present a sample of 12 Quasi-Stellar Objects (QSOs) potentially acting as strong gravitational lenses on background Emission Line Galaxies (ELG) or Lyman-α Emitters (LAEs) selected selected through a systematic search of the 297301 QSOs in the Sloan Digital Sky Survey (SDSS)-III Data Release 12. Candidates are identified by looking for compound spectra, where emission lines at a redshift larger than that of the quasar can be identified in the residuals after a QSO spectral template is subtracted from the observed spectra. The narrow diameter of BOSS fibers (2") then ensures that the object responsible for the additional emission lines must lie close to the line of sight of the QSO and hence provides a high probability of lensing. Among the 12 candidates identified, 9 have definite evidence for the presence of a background ELG identified by at least 4 higher-redshift nebular emission lines. The remaining 3 probable candidates present a strong asymmetrical emission line attributed to a background Lyman-α emitter (LAE). The QSO-ELG (QSO-LAE) lens candidates have QSO lens redshifts in the range 0.24 zQSO 0.66 (0.75 zQSO 1.23 ) and background galaxy redshifts in the range 0.48 zS,ELG 0.94 (2.17 zS,LAE 4.48). We show that the algorithmic search is complete at > 90 % for QSO-ELG systems, whereas it falls at 40 − 60% for QSO-LAE, depending on the redshift of the source. Upon confirmation of the lensing nature of the systems, this sample may quadruple the number of known QSOs acting as strong lenses. We have determined the completeness of our search, which allows future studies to compute lensing probabilities of galaxies by QSOs and differentiate between different QSO models. Future imaging of the full sample and lens modelling offers a unique approach to study and constrain key properties of QSOs.

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Three quasi-stellar objects acting as strong gravitational lenses

Cited by 23 publications

References 28 publications

Helium Reionization Simulations. I. Modeling Quasars as Radiation Sources

Helium Reionization Simulations. I. Modeling Quasars as Radiation Sources

A PCA-based automated finder for galaxy-scale strong lenses

Quasi-stellar objects acting as potential strong gravitational lenses in the SDSS-III BOSS survey

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