20 cm VLA Radio-Continuum Study of M31 - Images and Point Source Catalogues

TL;DR

This paper presents high-resolution, high-sensitivity radio-continuum images of M31 at 20 cm, cataloging 864 discrete sources, analyzing their properties, and comparing them with previous surveys to understand their nature.

Contribution

The study provides a comprehensive catalog of radio sources in M31 using merged VLA data, with improved sensitivity and resolution, and compares these sources to previous surveys for spectral analysis.

Findings

Identified 864 discrete radio sources in M31.

Detected a prominent ring feature with 706 mJy flux.

Found 61% of sources have non-thermal spectral indices.

Abstract

We present a series of new high-sensitivity and high-resolution radio-continuum images of M31 at \lambda=20 cm (\nu=1.4 GHz). These new images were produced by merging archived 20 cm radio-continuum observations from the Very Large Array (VLA) telescope. Images presented here are sensitive to rms=60 \mu Jy and feature high angular resolution (<10"). A complete sample of discrete radio sources have been catalogued and analysed across 17 individual VLA projects. We identified a total of 864 unique discrete radio sources across the field of M31. One of the most prominent regions in M31 is the ring feature for which we estimated total integrated flux of 706 mJy at \lambda=20 cm. We compare here, detected sources to those listed in Gelfand et al. (2004) at \lambda=92 cm and find 118 sources in common to both surveys. The majority (61%) of these sources exhibit a spectral index of \alpha <-0.6 indicating that their emission is predominantly non-thermal in nature. That is more typical for background objects.