J1721+8842: a gravitationally lensed binary quasar with a proximate damped Lyman-<i>α</i> absorber

Lemon, C.; Millon, M.; Sluse, Dominique; Courbin, F.; Auger, Matthew W.; Chan, J. H. H.; Paic, E.; Agnello, Adriano

doi:10.1051/0004-6361/202142138

Cited by 13 publications

(14 citation statements)

References 106 publications

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“…The system was originally discovered by Lemon et al (2019) who confirmed the source to be at z≈2.37, with strong absorption features. Gaia DR2 catalogues 5 detections, and an in-depth study of this system by Lemon et al (2022) show that there are two quasar sources at similar redshifts, with one being lensed into four images, and one into two images. They provide several mass models for the system, which we will compare to in Section 4.2.…”

Section: J1721+8842mentioning

confidence: 92%

“…For several systems, mass models based on ground-based imaging exist in the literature (e.g. Rusu & Lemon 2018;Lemon et al 2018Lemon et al , 2019Lemon et al , 2020Lemon et al , 2022. Given the difference in data resolution and depth, modeling approaches, treatment of perturbers, and parameterization it is difficult to perform a detailed quantitative comparison.…”

Section: Comparison To Published Mass Modelsmentioning

confidence: 99%

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STRIDES: automated uniform models for 30 quadruply imaged quasars

Schmidt

Treu

Birrer

et al. 2022

Monthly Notices of the Royal Astronomical Society

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Gravitational time delays provide a powerful one step measurement of H0, independent of all other probes. One key ingredient in time delay cosmography are high accuracy lens models. Those are currently expensive to obtain, both, in terms of computing and investigator time (105 − 6 CPU hours and ∼0.5–1 year, respectively). Major improvements in modeling speed are therefore necessary to exploit the large number of lenses that are forecast to be discovered over the current decade. In order to bypass this roadblock, we develop an automated modeling pipeline and apply it to a sample of 31 lens systems, observed by the Hubble Space Telescope in multiple bands. Our automated pipeline can derive models for 30/31 lenses with few hours of human time and <100 CPU hours of computing time for a typical system. For each lens, we provide measurements of key parameters and predictions of magnification as well as time delays for the multiple images. We characterize the cosmography-readiness of our models using the stability of differences in Fermat potential (proportional to time delay) w.r.t. modeling choices. We find that for 10/30 lenses our models are cosmography or nearly cosmography grade (<3 per cent and 3-5 per cent variations). For 6/30 lenses the models are close to cosmography grade (5-10 per cent). These results utilize informative priors and will need to be confirmed by further analysis. However, they are also likely to improve by extending the pipeline modeling sequence and options. In conclusion, we show that uniform cosmography grade modeling of large strong lens samples is within reach.

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Section: J1721+8842mentioning

confidence: 92%

Section: Comparison To Published Mass Modelsmentioning

confidence: 99%

STRIDES: automated uniform models for 30 quadruply imaged quasars

Schmidt

Treu

Birrer

et al. 2022

Monthly Notices of the Royal Astronomical Society

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show abstract

“…The 2D spectra were bias-subtracted and cosmic rays masked, and a model for the sky background based on the 5 either side of the object was subtracted. We extract separate spectra using a forward-modelling process, as described fully in Lemon et al (2022). Briefly, we forward model the quasar images as Moffat profiles onto a pixelised grid, and derive the 1D spatial spread function after applying a slit of 1 in width.…”

Section: Spectroscopic Follow-upmentioning

confidence: 99%

Discovery of strongly lensed quasars in the Ultraviolet Near Infrared Optical Northern Survey (UNIONS)

Chan

Lemon

Courbin

et al. 2022

A&A

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We report the discovery of five new doubly imaged lensed quasars from the first 2500 square degrees of the ongoing Canada-France Imaging Survey (CFIS), which is a component of the Ultraviolet Near Infrared Optical Northern Survey. The systems are preselected in the initial catalogues of either Gaia pairs or MILLIQUAS quasars. We then take advantage of the deep, 0.6″median-seeing r-band imaging of CFIS to confirm the presence of multiple point sources with similar colour of u − r via convolution of the Laplacian of the point spread function. Requiring point sources of similar colour and with flux ratios of less than 2.5 mag in r-band, we reduce the number of candidates from 256 314 to 7815. After visual inspection, we obtain 30 high-grade candidates, and prioritise a spectroscopic follow-up analysis for those showing signs of a lensing galaxy upon subtraction of the point sources. We obtain long-slit spectra for 18 candidates with ALFOSC on the 2.56-m Nordic Optical Telescope, confirming five new doubly lensed quasars with 1.21 < z < 3.36 and angular separations from 0.8″ to 2.5″. One additional system is a probable lensed quasar based on the CFIS imaging and existing SDSS spectrum. We further classify six objects as nearly identical quasars, that is, possible lenses but without the detection of a lensing galaxy. Given our recovery rate (83%) of existing optically bright lenses within the CFIS footprint, we expect that a similar strategy, coupled with u − r colour-selection from CFIS alone, will provide an efficient and complete discovery of small-separation lensed quasars of source redshifts below z = 2.7 within the CFIS r-band magnitude limit of 24.1 mag.

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“…The main observational difficulty comes from insufficient resolution of the imaging surveys that limits the minimum sep-aration between the detected pairs of Active Galactic Nuclei (AGN) to a few kiloparsecs (see e.g. Tang et al 2021;Chen et al 2022a;Lemon et al 2022, for recent discoveries). The higher resolution of radio observations offers the possibility to detect closer pairs (Rodriguez et al 2006), but this technique remains limited to the nearest galaxies and to a minimal separation of ∼ 10 pc, leaving the sub-parsec separation SMBHBs undetected.…”

Section: Introductionmentioning

confidence: 99%

Evidence for a milliparsec-separation Supermassive Binary Black Hole with quasar microlensing

Millon,

Dalang,

Lemon

et al. 2022

Preprint

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We report periodic oscillations in the 15-year long optical light curve of the gravitationally lensed quasar Q J0158−4325 at z s = 1.29. The signal is enhanced during a high magnification microlensing event undergone by the fainter lensed image, B, of the quasar, between 2003 and 2010. We measure a period of P o = 172.6 ± 0.9 days, translating into 75.4 ± 0.4 days in the quasar frame. The oscillations have a maximum amplitude of 0.25 mag, and decrease concurrently with the smooth microlensing amplitude. We explore four scenarios to explain the origin of the periodicity: 1-the high magnification microlensing event is due to a binary star in the lensing galaxy, 2-Q J0158−4325 contains a massive binary black hole system in its final dynamical stage before merging, 3-the quasar accretion disk contains a bright inhomogeneity in Keplerian motion around the black hole, and 4-the accretion disk is in precession. Among these four scenarios, only a binary supermassive black hole can account for both the short observed period and the amplitude of the signal, through the oscillation of the accretion disk towards and away from high-magnification regions of a microlensing caustic. The short measured period implies that the semi-long axis of the orbit is ∼ 10 −3 pc, and the coalescence timescale is t coal ∼ 1000 years, assuming that the decay of the orbit is solely powered by the emission of gravitational waves. The probability of observing a system so close to coalescence, in a sample of only 30 monitored lensed quasars, suggests either a much larger population of supermassive black hole binaries than predicted, or, more likely, that some other mechanism significantly increases the coalescence timescale. Three tests of the binary black hole hypothesis include: i) the recurrence of oscillations in photometric monitoring during any future microlensing events in either image, ii) spectroscopic detection of Doppler shifts (up to ∼0.01c) associated to optical emission in the vicinity of the black holes, and iii) the detection of gravitational waves through Pulsar Timing Array experiments, such as the SKA, which will have the sensitivity to detect the ∼100 nano-hertz emission.

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J1721+8842: a gravitationally lensed binary quasar with a proximate damped Lyman-α absorber

Cited by 13 publications

References 106 publications

STRIDES: automated uniform models for 30 quadruply imaged quasars

STRIDES: automated uniform models for 30 quadruply imaged quasars

Discovery of strongly lensed quasars in the Ultraviolet Near Infrared Optical Northern Survey (UNIONS)

Evidence for a milliparsec-separation Supermassive Binary Black Hole with quasar microlensing

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