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Abstract OH megamasers (OHMs) are extragalactic masers found primarily in gas-rich galaxy major mergers. To date, only ∼120 OHMs have been cataloged since their discovery in 1982, and efforts to identify distinct characteristics of OHM host galaxies have remained inconclusive. As radio astronomy advances with next-generation telescopes and extensive 21 cm Hisurveys, precursors to the Square Kilometre Array are expected to detect the 18 cm OH masing line with significantly increased frequency, potentially expanding the known OHM population tenfold. These detections, however, risk confusion with lower-redshift Hiemitters unless accompanied by independent spectroscopic redshifts. Building on methods proposed by Roberts et al. for distinguishing these interloping OHMs via near- to mid-IR photometry and emission line frequencies, we apply these techniques to data from the Arecibo Legacy Fast ALFA [AreciboL-band Feed Array] (ALFALFA) survey and a preliminary Aperture Tile In Focus (Apertif) Hiemission line catalog from the Westerbork Synthesis Radio Telescope. Our study, utilizing the Apache Point Observatory 3.5 m telescope to obtain optical spectroscopic redshifts of 142 candidates (107 from ALFALFA and 35 from Apertif), confirms five new OHM host galaxies and reidentifies two previously catalogued OHMs misclassified as Hiemitters in ALFALFA. These findings support the predictions from Roberts et al. and underscore the evolving landscape of radio astronomy in the context of next-generation telescopes. 

Abstract MeerKAT observations of the recently discovered, extremely low mass galaxy Pavo have revealed a neutral gas (Hi) reservoir that was undetected in archival Hisingle dish data. We measure Pavo’s Himass as $\log M_{\mathrm{HI}}/M_{\odot }=5.79\pm 0.05$, making it the lowest mass Hireservoir currently known in an isolated galaxy (with a robust distance measurement). Despite Pavo’s extreme isolation, with no known neighbor within over 700 kpc, its Hireservoir is highly disturbed. It does not show clear signs of rotation, and its center of mass is offset from the stellar body center by 320 pc, while its peak is offset by 82 pc (both in projection). Despite this disturbed morphology, Pavo still appears to be consistent with the Hisize–mass relation, although it is not possible to accurately determine a suitable inclination correction. Such disturbed, offset, and disorganized Hireservoirs are predicted by simulations of low-mass, star-forming dwarfs in which supernova-driven outflows efficiently disrupt the interstellar medium after a star formation (SF) event. It is likely that we are witnessing Pavo in precisely this period, tens to a few hundred Myr after a SF episode, when internal feedback has disrupted its gas reservoir.