The Discovery of QSOs Behind M31 and M33

Abstract

We report the discovery of 11 newly found quasars behind the stellar disks of the spiral galaxies M31 and M33 in the fields covered by the Local Group Galaxy Survey. Their redshifts range from 0.37 to 2.15. Most are X-ray, UV, and IR sources. We also report the discovery of 5 normal background galaxies. Most of these objects were observed owing to their anomalous colors, as part of a program (reported elsewhere) to confirm spectroscopically candidate red supergiant plus B star binaries; others were discovered as part of our identification of early-type massive stars based upon their optical colors. There are 15 previously known quasars in the same fields, for a grand total of 26, 15 behind M31 and 11 behind M33. Of these, only eight were discovered as part of surveys for quasars; the rest were found accidentally. The quasars are well distributed in the M31 and M33 fields, except for the inner regions, and have the potential for being good probes of the interstellar medium in these stellar disks, as well as serving as zero-point calibrators for Gaia parallaxes.

Accepted by the Astronomical Journal

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Cited by in corpus (10)

• DESI Observations of the Andromeda Galaxy: Revealing the Immigration History of our Nearest Neighbor
• The Red Supergiant Content of M31 and M33
• Anomaly detection in Hyper Suprime-Cam galaxy images with generative adversarial networks
• The Red Supergiant Binary Fraction as a Function of Metallicity in M31 and M33
• A machine-learning photometric classifier for massive stars in nearby galaxies I. The method
• Astronomaly at scale: searching for anomalies amongst 4 million galaxies
• Searching for Anomalies in the ZTF Catalog of Periodic Variable Stars
• A machine-learning photometric classifier for massive stars in nearby galaxies II. The catalog
• The Stripped-Star Ultraviolet Magellanic Cloud Survey (SUMS): The UV Photometric Catalog and Stripped Star Candidate Selection
• Quasars behind the disk of M31 galaxy