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

Publication date: 
Main author: 
Glowacki, Marcin
IAA authors: 
Hess, Kelley M.
Glowacki, Marcin;Collier, Jordan D.;Kazemi-Moridani, Amir;Frank, Bradley;Roberts, Hayley;Darling, Jeremy;Klöckner, Hans-Rainer;Adams, Nathan;Baker, Andrew J.;Bershady, Matthew;Blecher, Tariq;Blyth, Sarah-Louise;Bowler, Rebecca;Catinella, Barbara;Chemin, Laurent;Crawford, Steven M.;Cress, Catherine;Davé, Romeel;Deane, Roger;de Blok, Erwin;Delhaize, Jacinta;Duncan, Kenneth;Elson, Ed;February, Sean;Gawiser, Eric;Hatfield, Peter;Healy, Julia;Henning, Patricia;Hess, Kelley M.;Heywood, Ian;Holwerda, Benne W.;Hoosain, Munira;Hughes, John P.;Hutchens, Zackary L.;Jarvis, Matt;Kannappan, Sheila;Katz, Neal;Kereš, Dušan;Korsaga, Marie;Kraan-Korteweg, Renée C.;Lah, Philip;Lochner, Michelle;Maddox, Natasha;Makhathini, Sphesihle;Meurer, Gerhardt R.;Meyer, Martin;Obreschkow, Danail;Oh, Se-Heon;Oosterloo, Tom;Oppor, Joshua;Pan, Hengxing;Pisano, D. J.;Randriamiarinarivo, Nandrianina;Ravindranath, Swara;Schröder, Anja C.;Skelton, Rosalind;Smirnov, Oleg;Smith, Mathew;Somerville, Rachel S.;Srianand, Raghunathan;Staveley-Smith, Lister;Tanaka, Masayuki;Vaccari, Mattia;van Driel, Wim;Verheijen, Marc;Walter, Fabian;Wu, John F.;Zwaan, Martin A.
The Astrophysical Journal
Publication type: 
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 &gt; 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 <SUB>OH</SUB> = 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<SUP>-1</SUP>, and an integrated luminosity of (6.31 ± 0.18 [statistical] ± 0.31 [systematic]) × 10<SUP>3</SUP> L <SUB>⊙</SUB>, placing it among the most luminous OHMs known. The galaxy's far-infrared luminosity L <SUB>FIR</SUB> = (1.576 ±0.013) × 10<SUP>12</SUP> L <SUB>⊙</SUB> 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.
ADS Bibcode: 
Megamasers;Hydroxyl masers;Radio loud quasars;Galaxy mergers;Starburst galaxies;Ultraluminous infrared galaxies;1023;771;1349;608;1570;1735;Astrophysics - Astrophysics of Galaxies