Australia Telescope Compact Array observations of Fermi unassociated sources

TL;DR

This study used the Australia Telescope Compact Array to observe gamma-ray sources detected by Fermi, identifying radio counterparts and cataloging their properties to aid in source association.

Contribution

First radio observations of Fermi unassociated sources at 5 and 9 GHz, providing a catalog of potential counterparts and their spectral characteristics.

Findings

Detected 424 radio sources within gamma-ray error regions.

Identified 84 sources with flat spectral indices.

Approximately one-third of sources have high association probability.

Abstract

We report results of the first phase of observations with the Australia Telescope Compact Array (ATCA) at 5 and 9 GHz of the fields around 411 gamma-ray sources with declinations < +10 deg detected by Fermi but marked as unassociated in the 2FGL catalogue. We have detected 424 sources with flux densities in a range of 2 mJy to 6 Jy that lie within the 99 per cent localisation uncertainty of 283 gamma-ray sources. Of these, 146 objects were detected in both the 5 and 9 GHz bands. We found 84 sources in our sample with a spectral index flatter than -0.5. The majority of detected sources are weaker than 100 mJy and for this reason were not found in previous surveys. Approximately 1/3 of our sample, 128 objects, have the probability of being associated by more than 10 times than the probability of being a background source found in the vicinity of a gamma-ray object by chance. We present the catalogue of positions of these sources, estimates of their flux densities and spectral indices where available.