The Magellanic Quasars Survey. III. Spectroscopic Confirmation of 758 AGNs Behind the Magellanic Clouds

TL;DR

The Magellanic Quasars Survey significantly increased the known quasars behind the Magellanic Clouds, providing a valuable resource for variability, motion, and interstellar medium studies through spectroscopic confirmation of 758 quasars.

Contribution

This study is the first large-scale spectroscopic confirmation of quasars behind the Magellanic Clouds, expanding the known sample by nearly tenfold and enabling diverse astrophysical research.

Findings

Confirmed 758 quasars behind the Magellanic Clouds.

94% of these quasars are newly identified.

Provided a dense grid for proper motion and absorption studies.

Abstract

The Magellanic Quasars Survey (MQS) has now increased the number of quasars known behind the Magellanic Clouds by almost an order of magnitude. All survey fields in the Large Magellanic Cloud (LMC) and 70% of those in the Small Magellanic Cloud (SMC) have been observed. The targets were selected from the third phase of the Optical Gravitational Lensing Experiment (OGLE-III) based on their optical variability, mid-IR and/or X-ray properties. We spectroscopically confirmed 758 (565 LMC and 193 SMC) quasars behind the Clouds, of which 94% (527 LMC and 186 SMC) are newly identified. The MQS quasars have long-term (12 years and growing for OGLE), high-cadence light curves, enabling unprecedented variability studies of quasars. The MQS quasars also provide a dense reference grid for measuring both the internal and bulk proper motions of the Clouds, and 50 quasars are bright enough (I<18 mag) for absorption studies of the interstellar/galactic (ISM/IGM) medium of the Clouds.