A 325-MHz GMRT survey of the Herschel-ATLAS/GAMA fields

TL;DR

This paper presents a comprehensive 325-MHz radio survey of the Herschel-ATLAS/GAMA fields using GMRT, resulting in a catalog of over 5000 sources and insights into their spectral properties, aiding studies of galaxy evolution.

Contribution

It provides the first large-area 325-MHz GMRT survey of the H-ATLAS/GAMA fields with automated data processing and source cataloging, expanding low-frequency radio data for galaxy studies.

Findings

Cataloged 5263 sources brighter than 5 sigma.

Spectral indices broadly agree with previous results.

No flattening of spectral index below 10 mJy at 1.4 GHz.

Abstract

We describe a 325-MHz survey, undertaken with the Giant Metrewave Radio Telescope (GMRT), which covers a large part of the three equatorial fields at 9, 12 and 14.5 h of right ascension from the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) in the area also covered by the Galaxy And Mass Assembly survey (GAMA). The full dataset, after some observed pointings were removed during the data reduction process, comprises 212 GMRT pointings covering ~90 deg^2 of sky. We have imaged and catalogued the data using a pipeline that automates the process of flagging, calibration, self-calibration and source detection for each of the survey pointings. The resulting images have resolutions of between 14 and 24 arcsec and minimum rms noise (away from bright sources) of ~1 mJy/beam, and the catalogue contains 5263 sources brighter than 5 sigma. We investigate the spectral indices of GMRT sources which are also detected at 1.4 GHz and find them to agree broadly with previously published results; there is no evidence for any flattening of the radio spectral index below S_1.4=10 mJy. This work adds to the large amount of available optical and infrared data in the H-ATLAS equatorial fields and will facilitate further study of the low-frequency radio properties of star formation and AGN activity in galaxies out to z~1.