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

## TL;DR

This study measures the time delay, microlensing effects, and intervening metal absorption in the gravitationally lensed quasar SDSS J1442+4055, providing data useful for cosmology and galaxy evolution studies.

## Contribution

It presents new spectroscopic and photometric measurements of the lens system, including a precise time delay and characterization of the intervening metal-rich absorber.

## Key findings

- Time delay of 25.0 ± 1.5 days between images A and B.
- Detection of a dust extinction bump at 2209 Å in the intervening system.
- Spectroscopic confirmation of the lensing galaxy at z = 0.284.

## 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 $\pm$ 1.5 days (1$\sigma$ 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 early--type 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 $z \sim$ 2. This dusty absorber is responsible for an extinction bump at a rest--frame wavelength of 2209 $\pm$ 2 \AA, which has strengths of $\sim$ 0.47 and 0.76 mag $\mu$m$^{-1}$ 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.