Spectroscopy of lensing galaxies in the GTC era

TL;DR

This study uses GTC/OSIRIS spectroscopy to analyze faint galaxies near gravitationally lensed quasars, providing insights into the lensing galaxies' contributions and challenging simple lens models.

Contribution

It presents new spectroscopic data of galaxies near lens systems, revealing complexities in lens composition and external shear contributions.

Findings

One galaxy in the Cloverleaf field has negligible external shear contribution.

Spectra suggest the main lens in SDSS 1116+4118 is not a single galaxy.

Spectroscopic analysis constrains the nature of lensing galaxies.

Abstract

We are using OSIRIS at the 10.4-m Gran Telescopio CANARIAS (GTC) to obtain spectra of faint galaxies close to multiply imaged quasars. We initially focused on the fields of HE 1413+117 (Cloverleaf quasar) and SDSS 1116+4118. In this contribution, we present long-slit spectroscopy of two galaxies in the southwest of the Cloverleaf, and show that one of them makes a negligible contribution to the external shear of the gravitational lens system. Spectra of the main lensing galaxy candidate in SDSS 1116+4118 are also analysed and discused. If gravitational lensing is causing the quasar image splitting, our spectra reveal that the main lens can not consist of only one dominant galaxy.