Looking at the Distant Universe with the MeerKAT Array: Discovery of a Luminous OH Megamaser at z > 0.5

Marcin Glowacki , Jordan D. Collier , Amir Kazemi-Moridani , Bradley Frank , Hayley Roberts , Jeremy Darling , Hans-Rainer Klöckner , Nathan Adams , Andrew J. Baker , Matthew Bershady , Tariq Blecher , Sarah-Louise Blyth , Rebecca Bowler , Barbara Catinella , Laurent Chemin , Steven M. Crawford , Catherine Cress , Romeel Davé , Roger Deane , Erwin de Blok , Jacinta Delhaize , Kenneth Duncan , Ed Elson , Sean February , Eric Gawiser , Peter Hatfield , Julia Healy , Patricia Henning , Kelley M. Hess , Ian Heywood , Benne W. Holwerda , Munira Hoosain , John P. Hughes , Zackary L. Hutchens , Matt Jarvis , Sheila Kannappan , Neal Katz , Dušan Kereš , Marie Korsaga (1) , Renée C. Kraan-Korteweg , Philip Lah , Michelle Lochner , Natasha Maddox , Sphesihle Makhathini , Gerhardt R. Meurer , Martin Meyer , Danail Obreschkow , Se-Heon Oh , Tom Oosterloo , Joshua Oppor , Hengxing Pan , D. J. Pisano , Nandrianina Randriamiarinarivo , Swara Ravindranath , Anja C. Schröder , Rosalind Skelton , Oleg Smirnov , Mathew Smith (2) , Rachel S. Somerville , Raghunathan Srianand , Lister Staveley-Smith , Masayuki Tanaka , Mattia Vaccari , Wim van Driel (3) , Marc Verheijen , Fabian Walter , John F. Wu , Martin A. Zwaan

1 ObAS - Observatoire astronomique de Strasbourg
2 IP2I Lyon - Institut de Physique des 2 Infinis de Lyon
3 GEPI - Galaxies, Etoiles, Physique, Instrumentation

In the local universe, OH megamasers (OHMs) are detected almost exclusively in infrared-luminous galaxies, with a prevalence that increases with IR luminosity, suggesting that they trace gas-rich galaxy mergers. Given the proximity of the rest frequencies of OH and the hyperfine transition of neutral atomic hydrogen (H I), radio surveys to probe the cosmic evolution of H I in galaxies also offer exciting prospects for exploiting OHMs to probe the cosmic history of gas-rich mergers. Using observations for the Looking At the Distant Universe with the MeerKAT Array (LADUMA) deep H I survey, we report the first untargeted detection of an OHM at z > 0.5, LADUMA J033046.20-275518.1 (nicknamed "Nkalakatha"). The host system, WISEA J033046.26-275518.3, is an infrared-luminous radio galaxy whose optical redshift z ≍ 0.52 confirms the MeerKAT emission-line detection as OH at a redshift z _OH = 0.5225 ± 0.0001 rather than H I at lower redshift. The detected spectral line has 18.4σ peak significance, a width of 459 ± 59 km s^-1, and an integrated luminosity of (6.31 ± 0.18 [statistical] ± 0.31 [systematic]) × 10³ L _⊙, placing it among the most luminous OHMs known. The galaxy's far-infrared luminosity L _FIR = (1.576 ±0.013) × 10¹² L _⊙ marks it as an ultraluminous infrared galaxy; its ratio of OH and infrared luminosities is similar to those for lower-redshift OHMs. A comparison between optical and OH redshifts offers a slight indication of an OH outflow. This detection represents the first step toward a systematic exploitation of OHMs as a tracer of galaxy growth at high redshifts.

Keywords: Megamasers; Hydroxyl masers; Radio loud quasars; Galaxy mergers; Starburst galaxies; Ultraluminous infrared galaxies

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]

Marcin Glowacki, Jordan D. Collier, Amir Kazemi-Moridani, Bradley Frank, Hayley Roberts, et al.. Looking at the Distant Universe with the MeerKAT Array: Discovery of a Luminous OH Megamaser at z > 0.5. The Astrophysical journal letters, 2022, 931, pp.L7. ⟨10.3847/2041-8213/ac63b0⟩. ⟨insu-03707835⟩