frequencies just above 1420 MHz, sensitive sky surveys might detect OH masers, which could be mistaken for a population of “infalling, compact High Velocity Clouds” but would ultimately be traced to luminous FIR background galaxies at $z \approx 0.17$ once optical and IR follow-up has been performed.
author:
- 'F. H. Briggs'
date: 'Received 30 September 1997; accepted 20 May 1998'
title: 'Cosmologically distant OH megamasers: A test of the galaxy merging rate at $Z \approx 2$ and a contaminant of blind HI surveys in the 21cm line'
---

Introduction
============

The detectability of OH megamaser and gigamaser galaxies at cosmological distances has been noted by several authors (Baan 1989, Baan et al 1992a, Norman & Braun 1996, Baan 1997). So far, the sample of known megamasers has been assembled from targeted observations of luminous galaxies for which redshifts are known (cf. Baan et al 1992b, Martin et al 1989, Stavely-Smith et al 1992). The receiving systems are tuned to the predicted frequencies of the redshifted OH lines whose rest frequencies fall at 1665 and 1667 MHz. The greatest success rate for discovery of megamasers occurs in galaxy samples that are selected for having the highest far infrared (FIR) 60 