MeerKAT discovery of a high-redshift strongly-lensed hydroxyl gigamaser

TL;DR

This paper reports the discovery of the most distant hydroxyl megamaser at redshift 1.027 using MeerKAT, demonstrating the potential of new radio telescopes to explore high-redshift galaxy mergers and starbursts.

Contribution

First detection of a high-redshift hydroxyl megamaser at z=1.027 with detailed spectral analysis using MeerKAT, expanding the observable universe of OHMs.

Findings

Discovered a luminous OHM at z=1.027

Detected complex spectral components in the OHM

Identified a new H I absorption line

Abstract

At low redshifts, hydroxyl megamasers (OHMs) have been shown to trace galaxy mergers, obscured starbursts, high molecular gas densities, and candidate dual supermassive black hole systems. Given this astrophysical utility, exploring these sources at larger cosmological look-back times is therefore of key interest. While previous OHM surveys have been limited to redshifts of $z \lesssim 0.25$, the ability to expand the OHM frontier is significantly enhanced with new high-sensitivity radio facilities such as MeerKAT. In this Letter, we report the discovery of an OHM in the gravitational lens system HATLAS J142935.3-002836 at $z = 1.027$, the most distant OHM source yet detected. The spectrum has blended 1667 and 1665 MHz emission and exhibits a highly complex profile, with spectral components ranging in widths of $<8$ km s$^{-1}$ to $\sim300$ km s$^{-1}$. The integrated (magnification uncorrected) luminosity of log($L_{\rm OH} / L_{\odot}$) = 5.51 $\pm$ 0.67 makes this the most apparently luminous OHM known to date. In the same wide-band dataset, we have also detected a previously unknown ${\rm H I}$ absorption line. The signal-to-noise ratio of over 150 with just a 4.7 h observation highlights the potential that MeerKAT and the future Square Kilometre Array mid-frequency array offer to explore the high-redshift OHM universe.