Spectral index properties of milliJansky radio sources

TL;DR

This study investigates the spectral index properties of faint radio sources at 843 MHz, finding no significant flattening trend at lower flux densities and exploring their redshift and infrared characteristics.

Contribution

It provides a new catalogue of 843 MHz radio sources with spectral index distributions and examines their properties across flux densities and redshifts.

Findings

No significant spectral index flattening at lower flux densities.

Spectral index distribution analyzed as a function of redshift.

Initial properties of faint Compact Steep Spectrum sources presented.

Abstract

At the faintest radio flux densities (S_1.4 < 10 mJy), conflicting results have arisen regarding whether there is a flattening of the average spectral index between a low radio frequency (325 or 610 MHz), and e.g. 1.4 GHz. We present a new catalogue of 843 MHz radio sources in the ELAIS-S1 field that contains the sources, their ATLAS counterparts, and the spectral index distributions of the sources as a function of flux density. We do not find any statistically significant evidence for a trend towards flatter spectral indices with decreasing flux density. We then investigate the spectral index distribution with redshift for those sources with reliable redshifts and explore the infrared properties. An initial sample of faint Compact Steep Spectrum sources in ATLAS is also presented, with a brief overview of their properties.