the OH masers from the HI lines from normal galaxies of low redshift would be straightforward. High spatial resolution radio observations would show OH masers to have high brightness temperature and would identify the sources with compact optical sources for which emission lines would provide an unambiguous redshift. OH megamasers are strong emitters of 60 $\mu$m infrared, but sources at $z\approx 0.17$ (or greater), selected for OH line strength around 1 mJy, will have 60 $\mu$m flux densities approximately equal or less than the 0.2 Jy sensitivity level of the IRAS 60 $\mu$m Faint Source Survey (Moshir et al 1992). Since the infrared spectrum of the OH megamasers falls steeply from 60 $\mu$m to 25 $\mu$m, suitable megamaser host galaxies at moderate to high redshift may become increasingly difficult to detect at infrared wavelengths as the 60 $\mu$m flux is redshifted toward still longer wavelengths.

Redshift dependent merging rate
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The importance of merging small galaxies to build the large galaxies that we observe at the present is a topic of considerable controversy, since the question addresses the foundations for theories of galaxy formation. In this section, it is demonstrated that surveys sensitive to OH masers at $z\approx 2$ may 