A Mock Catalog of Gravitationally Lensed Quasars for the LSST Survey

TL;DR

This paper creates a detailed simulated catalog of gravitationally lensed quasars for LSST, predicting their numbers, properties, and observational features to aid future searches.

Contribution

It introduces a comprehensive mock catalog of lensed quasars for LSST, incorporating recent quasar and galaxy data, and estimates their detectability and characteristics.

Findings

LSST will discover approximately 2,400 lensed quasars.

About 200 of these will be quadruply-lensed systems.

Most lensed quasars will have image separations >0.5 arcseconds.

Abstract

We present a mock catalog of gravitationally lensed quasars at $z_\text{qso}<7.5$ with simulated images for the Rubin Observatory Legacy Survey of Space and Time (LSST). We adopt recent measurements of quasar luminosity functions to model the quasar population, and use the CosmoDC2 mock galaxy catalog to model the deflector galaxies, which successfully reproduces the observed galaxy velocity dispersion functions up to $z_d\sim1.5$. The mock catalog is highly complete for lensed quasars with Einstein radius $\theta_E>0\farcs07$ and quasar absolute magnitude $M_{i}<-20$. We estimate that there are $\sim10^3$ lensed quasars discoverable in current imaging surveys, and LSST will increase this number to $\sim2.4\times10^3$. Most of the lensed quasars have image separation $\Delta \theta>0\farcs5$, which will at least be marginally resolved in LSST images with seeing of $\sim0\farcs7$. There will be $\sim200$ quadruply-lensed quasars discoverable in the LSST. The fraction of quad lenses among all discoverable lensed quasars is about $\sim10\%-15\%$, and this fraction decreases with survey depth. This mock catalog shows a large diversity in the observational features of lensed quasars, in terms of lensing separation and quasar-to-deflector flux ratio. We discuss possible strategies for a complete search of lensed quasars in the LSST era.