High-resolution imaging follow-up of doubly imaged quasars

TL;DR

This study presents three years of follow-up imaging of 57 quasar lens candidates, confirming 15 new lenses, modeling their properties, and analyzing flux ratio deviations to aid future astrophysical research.

Contribution

It provides a new sample of 15 confirmed quasar lenses, detailed modeling of their properties, and insights into flux ratio deviations in lens systems.

Findings

15 new quasar lenses confirmed

Flux ratio deviations are similar in double and quadruple lenses

Provides lens properties and predicted time delays for follow-up studies

Abstract

We report upon three years of follow-up and confirmation of doubly imaged quasar lenses through imaging campaigns from 2016-2018 with the Near-Infrared Camera2 (NIRC2) on the W. M. Keck Observatory. A sample of 57 quasar lens candidates are imaged in adaptive-optics-assisted or seeing-limited $K^\prime$-band observations. Out of these 57 candidates, 15 are confirmed as lenses. We form a sample of 20 lenses adding in a number of previously-known lenses that were imaged with NIRC2 in 2013-14 as part of a pilot study. By modelling these 20 lenses, we obtain $K^\prime$-band relative photometry and astrometry of the quasar images and the lens galaxy. We also provide the lens properties and predicted time delays to aid planning of follow-up observations necessary for various astrophysical applications, e.g., spectroscopic follow-up to obtain the deflector redshifts for the newly confirmed systems. We compare the departure of the observed flux ratios from the smooth-model predictions between doubly and quadruply imaged quasar systems. We find that the departure is consistent between these two types of lenses if the modelling uncertainty is comparable.