Gravitationally Lensed Quasar SDSS J1442+4055: Redshifts of Lensing Galaxies, Time Delay, Microlensing Variability, and Intervening Metal System at z ∼ 2

Abstract

We present an r-band photometric monitoring of the two images A and B of the gravitationally lensed quasar SDSS J1442+4055 using the Liverpool Telescope (LT). From the LT light curves between 2015 December and 2018 August, we derive at once a time delay of 25.0 ± 1.5 days (1σ confidence interval; A is leading) and microlensing magnification gradients below 10 −4 mag day −1 . The delay interval is not expected to be affected by an appreciable microlensing-induced bias, so it can be used to estimate cosmological parameters. This paper also focuses on new Gran Telescopio Canarias (GTC) and LT spectroscopic observations of the lens system. We determine the redshift of two bright galaxies around the doubly imaged quasar using LT spectroscopy, while GTC data lead to low-noise individual spectra of A, B, and the main lensing galaxy G1. The G1 spectral shape is accurately matched to an earlytype galaxy template at z = 0.284, and it has potential for further relevant studies. Additionally, the quasar spectra show absorption by metal-rich gas at z ∼ 2. This dusty absorber is responsible for an extinction bump at a rest-frame wavelength of 2209 ± 2Å, which has strengths of ∼ 0.47 and 0.76 mag µm −1 for A and B, respectively. In such intervening system, the dust-to-gas ratio, gas-phase metallicity indicator [Zn/H], and dust depletion level [Fe/Zn] are relatively high.

Time-Delay Cosmography: Measuring the Hubble Constant and Other Cosmological Parameters with Strong Gravitational Lensing

“… 2007 ; Goicoechea and Shalyapin 2016 ; Giannini et al. 2017 ; Shalyapin and Goicoechea 2019 ), about 40 lensed quasars have now known time delays, although with variable precision, but the sample starts to be sufficiently large to vastly reduce the random uncertainties and to enable a statistical study of the time-delay lenses. In addition, three cluster-scale lensed quasars have measured time delays (Fohlmeister et al.…”

TDCOSMO II: 6 new time delays in lensed quasars from high-cadence monitoring at the MPIA 2.2m telescope

“…As a result, it typically requires 5 to 10 seasons of monitoring to obtain enough prominent features in the light curves to unambiguously match the intrinsic variations in the different multiple images without being affected by the extrinsic variations. This long-term strategy yielded several precise time-delay measurements (Tewes et al 2013b;Rathna Kumar et al 2013;Shalyapin & Goicoechea 2017;Bonvin et al 2017;Shalyapin & Goicoechea 2019;Millon et al 2020), but at a large observational cost. It is no longer sustainable in the era of wide field surveys such as DES, CFIS, PanSTARRS, Gaia, which are discovering dozens of new lensed quasars.…”