SDSS J1640+1932: a spectacular galaxy–quasar strong lens system

Wang, Lin; Shu, Y.; Li, Ran; Zhang, Zheng; Wen, Z. L.; Liu, Guilin

doi:10.1093/mnras/stx733

Cited by 6 publications

(6 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…with two or more emission or absorption lines falling at a different and concordant redshift, higher than the LRG redshift, and indicating the presence of a background galaxy. Two of them are already published as confirmed strong lens systems: PS1J2343−0030 as part of the SLACS sample (Auger et al 2009), and PS1J1640+1932 (lensed quasar from Wang et al 2017). Thirdly, we find eight LRG-like spectra overlaid with a single bright, high-redshift emission line consistent with [OII]λλ3727 from a background star-forming galaxy at Finding a vast majority of LRGs 15 and only 3/104 starforming galaxies at lower redshift demonstrates the validity of our method.…”

Section: Ancillary Spectroscopysupporting

confidence: 68%

See 1 more Smart Citation

Holismokes

Cañameras

Schuldt

Suyu

et al. 2020

A&A

View full text Add to dashboard Cite

We present a systematic search for wide-separation (with Einstein radius θE ≳ 1.5″), galaxy-scale strong lenses in the 30 000 deg2 of the Pan-STARRS 3π survey on the Northern sky. With long time delays of a few days to weeks, these types of systems are particularly well-suited for catching strongly lensed supernovae with spatially-resolved multiple images and offer new insights on early-phase supernova spectroscopy and cosmography. We produced a set of realistic simulations by painting lensed COSMOS sources on Pan-STARRS image cutouts of lens luminous red galaxies (LRGs) with redshift and velocity dispersion known from the sloan digital sky survey (SDSS). First, we computed the photometry of mock lenses in gri bands and applied a simple catalog-level neural network to identify a sample of 1 050 207 galaxies with similar colors and magnitudes as the mocks. Second, we trained a convolutional neural network (CNN) on Pan-STARRS gri image cutouts to classify this sample and obtain sets of 105 760 and 12 382 lens candidates with scores of pCNN > 0.5 and > 0.9, respectively. Extensive tests showed that CNN performances rely heavily on the design of lens simulations and the choice of negative examples for training, but little on the network architecture. The CNN correctly classified 14 out of 16 test lenses, which are previously confirmed lens systems above the detection limit of Pan-STARRS. Finally, we visually inspected all galaxies with pCNN > 0.9 to assemble a final set of 330 high-quality newly-discovered lens candidates while recovering 23 published systems. For a subset, SDSS spectroscopy on the lens central regions proves that our method correctly identifies lens LRGs at z ∼ 0.1–0.7. Five spectra also show robust signatures of high-redshift background sources, and Pan-STARRS imaging confirms one of them as a quadruply-imaged red source at zs = 1.185, which is likely a recently quenched galaxy strongly lensed by a foreground LRG at zd = 0.3155. In the future, high-resolution imaging and spectroscopic follow-up will be required to validate Pan-STARRS lens candidates and derive strong lensing models. We also expect that the efficient and automated two-step classification method presented in this paper will be applicable to the ∼4 mag deeper gri stacks from the Rubin Observatory Legacy Survey of Space and Time (LSST) with minor adjustments.

show abstract

Section: Ancillary Spectroscopysupporting

confidence: 68%

“…Finally, two of these 23 published systems are confirmed lensed quasars. PS1J2350+3654 (p CNN = 1.0 and grade of 2.25) was discovered in Gaia DR2 (Lemon et al 2019), and PS1J1640+1932 (p CNN = 1.0 and grade of 2.25) from SDSS (Wang et al 2017).…”

Section: Final Candidates From Visual Inspectionmentioning

confidence: 99%

Holismokes

Cañameras

Schuldt

Suyu

et al. 2020

A&A

View full text Add to dashboard Cite

show abstract

“…Only two lens systems have a component with no modelled W1 or W2 flux, both with Gaia detections separated by less than 1 arcsecond: SDSSJ1640+1932 (Wang et al 2017) and SDSSJ0248+1913 (Ostrovksi et al in prep., Delchambre et al 2018). However, 21 such examples exist in the quasar+star sample.…”

Section: Modelling Unwise Pixelsmentioning

confidence: 99%

Gravitationally lensed quasars in Gaia – II. Discovery of 24 lensed quasars

Lemon

Auger

McMahon

et al. 2018

Monthly Notices of the Royal Astronomical Society

106

View full text Add to dashboard Cite

We report the discovery and spectroscopic confirmation of 22 new gravitationally lensed quasars found using Gaia data release 2. The selection was made using several techniques: multiple Gaia detections around objects in quasar candidate catalogues, modelling of unWISE coadd pixels using Gaia astrometry, and Gaia detections offset from photometric and spectroscopic galaxies. Spectra of 33 candidates were obtained with the William Herschel Telescope, 22 of which are lensed quasars, 2 highly probably lensed quasars, 5 nearly identical quasar pairs, 1 inconclusive system, and 3 contaminants. Of the 3 confirmed quadruply imaged systems, J2145+6345 is a 2.1 arcsecond separation quad with 4 bright images (G=16. 86, 17.26, 18.34, 18.56), making it ideal for time delay monitoring. Analysing this new sample alongside known lenses in the Pan-STARRS footprint, and comparing to expected numbers of lenses, we show that, as expected, we are biased towards systems with bright lensing galaxies and low source redshifts. We discuss possible techniques to remove this bias from future searches. A |b|>20 complete sample of lensed quasars detected by Gaia and with image separations above 1 arcsecond will provide a valuable statistical sample of around 350 systems. Currently only 96 known lenses satisfy these criteria, yet promisingly, our unWISE modelling technique is able to recover all of these with simple WISE-Gaia colour cuts that remove ∼80 per cent of previously followed-up contaminants. Finally, we provide an online database of known lenses, quasar pairs, and contaminant systems.

show abstract

“…Here we present in greater detail the lensing probability calculation of Broadhurst et al (2018) and extend the discussion for the situation where microlenses are present.We do not discuss the case of QSO lensing since magnifications in this case are not as extreme as in the case of stars, SNe or GW. The magnifications involved in QSO lensing is normally modest reaching values of µ ∼ few hundred at most (Walsh et al 1979;Weymann et al 1980;Wang et al 2017). This limitation in the magnification follows from the much larger size of accretion discs which are orders of magnitude larger than stars or SNe (except for when QSOs are observed at X-ray wavelegths, in which case the size of the X-ray emitting region can be considerably smaller, and comparable to the size of a SNe Mosquera et al 2013).…”

mentioning

confidence: 99%

The Universe at extreme magnification

Diego

2019

A&A

View full text Add to dashboard Cite

Extreme magnifications of distant objects by factors of several thousand have recently become a reality. Small very luminous compact objects, such as supernovae (SNe), giant stars at z = 1 -2, Pop III stars at z > 7 and even gravitational waves from merging binary black holes near caustics of gravitational lenses can be magnified to many thousands or even tens of thousands thanks to their small size. We explore the probability of such extreme magnifications in a cosmological context including also the effect of microlenses near critical curves. We show how a natural limit to the maximum magnification appears due to the presence of microlenses near critical curves. We use a combination of state of the art halo mass functions, high-resolution analytical models for the density profiles and inverse ray tracing to estimate the probability of magnification near caustics. We estimate the rate of highly-magnified events in the case of SNe, GW and very luminous stars including Pop III stars. Our findings reveal that future observations will increase the number of events at extreme magnifications opening the door not only to study individual sources at cosmic distances but also to constrain compact dark matter candidates.A&A proofs: manuscript no. main of it), as well as the observation of the relatively abundant low frequency LIGO events. In this work we estimate the probability of observing, not only luminous stars at z > 1 but also discuss other very compact but intrinsically energetic phenomena, such as SNe, or GW.In order to observe distant gravitationally lensed objects, one needs large magnification factors that compensate for the increase in luminosity distance. The smaller probability of lensing is partially compensated by the larger volume which, between z ≈ 0.3 and z ≈ 1.3, grows approximately as (1 + z) 3 (and at a slower rate at higher redshifts). More precisely, the volume per redshift interval peaks at z ≈ 2.5 (with about 55 Gpc 3 in a redshift interval of thickness ∆z = 0.1). Regarding the probability of lensing, background objects at high redshifts have a higher probability of intersecting a gravitational lens along the line of sight. This probability is described by the optical depth. It is well known that the optical depth grows rapidly between z=0 and z=1. Between z=1 and z=3 it continues to grow although at a much slower pace. Beyond z =3 -5, the optical depth is still growing but much more slowly and beyond z =5 it only grows by percent values, specially if one considers large magnification factors where the presence of caustics is required (these caustics are expected to be rare for lenses beyond z ≈ 3). For sources (or events) that trace the star formation history, and at redshifts of the background source between 1 and 3, the small probability of magnification factors can be compensated by the larger volume element and increased volumetric density. In this redshift interval, the probability of seeing extremely magnified events can be maximum.Examples of extreme magnification are the aforementioned ...

show abstract

SDSS J1640+1932: a spectacular galaxy–quasar strong lens system

Cited by 6 publications

References 47 publications

Holismokes

Holismokes

Gravitationally lensed quasars in Gaia – II. Discovery of 24 lensed quasars

The Universe at extreme magnification

Contact Info

Product

Resources

About