Fermi Unassociated Sources in the MeerKAT Absorption Line Survey

TL;DR

This study uses MeerKAT radio data to identify steep spectrum radio sources within Fermi unassociated gamma-ray sources, leading to potential pulsar and high-redshift galaxy candidates, demonstrating the survey's high sensitivity and future potential.

Contribution

The paper presents a new method combining radio spectral data and optical/infrared classification to identify pulsar and galaxy candidates among Fermi unassociated sources.

Findings

Identified nine pulsar candidates for follow-up pulsation searches.

Reported 41 steep spectrum radio galaxy candidates, potential high-redshift objects.

Showed MeerKAT's capability to detect 80% of known pulsars.

Abstract

Over 2000 Gamma ray sources identified by the Large Area Telescope (LAT) on NASA's Fermi Gamma-ray Space Telescope are considered unassociated, meaning that they have no known counterparts in any other frequency regime. We have carried out an image-based search for steep spectrum radio sources, with in-band spectral index less than -1.4, within the error regions of Fermi unassociated sources using 1 to 1.4 GHz radio data from the MeerKAT Absorption Line Survey (MALS) Data Release. MALS DR1 with a median rms noise of 22 to 25 microJy and 735,649 sources is a significant advance over past image-based searches with improvements in sensitivity, resolution and bandwidth. Steep spectrum candidates were identified using a combination of in-band spectral indices from MALS and existing radio surveys. We developed an optical and infrared source classification scheme in order to distinguish between galactic pulsars and radio galaxies. In total, we identify nine pulsar candidates towards six Fermi sources that are worthy of follow-up for pulsation searches. We also report 41 steep spectrum radio galaxy candidates that may be of interest in searches for high-redshift radio galaxies. We show that MALS due to its excellent continuum sensitivity can detect 80 percent of the known pulsar population. This exhibits the promise of identifying exotic pulsar candidates with future image-based surveys with the Square Kilometre and its precursors.