The remnant radio galaxy associated with NGC 1534

TL;DR

This paper reports on the discovery and analysis of a remnant radio galaxy associated with NGC 1534, revealing its spectral age, magnetic field structure, and star-formation history through new radio observations.

Contribution

It provides detailed radio observations and spectral analysis of a remnant radio galaxy, highlighting its age, magnetic field, and star-formation rate, which enhances understanding of such rare objects.

Findings

Spectral age of 203 Myr for the emission

Radio-derived star-formation rate of 0.38 M_sun/yr

Unusual circular magnetic field pattern in the northern lobe

Abstract

We present new observations of the large-scale radio emission surrounding the lenticular galaxy NGC~1534 with the Australia Telescope Compact Array and Murchison Widefield Array. We find no significant compact emission from the nucleus of NGC 1534 to suggest an active core, and instead find low-power radio emission tracing its star-formation history with a radio-derived star-formation rate of $0.38\pm0.03$ M$_\odot$ yr$^{-1}$. The spectral energy distribution of the extended emission is well-fit by a continuous injection model with an 'off' component, consistent with dead radio galaxies. We find the spectral age of the emission to be 203 Myr, having been active for 44 Myr. Polarimetric analysis points to both a large-scale magneto-ionic Galactic foreground at $+33$ rad m$^{-2}$ and a component associated with the northern lobe of the radio emission at $-153$ rad m$^{-2}$. The magnetic field of the northern lobe shows an unusual circular pattern of unknown origin. While such remnant sources are rare, combined low- and high-frequency radio surveys with high surface-brightness sensitivities are expected to greatly increase their numbers in the coming decade, and combined with new optical and infrared surveys should provide a wealth of information on the hosts of the emission.