Searching for new OH megamasers out to redshifts z>1

Abstract

We have carried out a search for 18-cm OH megamaser (OHM) emission with the Green Bank Telescope. The targeted galaxies comprise a sample of 121 ULIRGs at 0.09 0.25. Nine new detections of OHMs are reported, all at redshifts z<0.25. For the remainder of the galaxies, observations constrain the upper limit on OH emission; this rules out OHMs of moderate brightness (LOH >103 L) for 26% of the sample, and extremely bright OHM emission (LOH >104 L) for 73% of the sample. Losses from RFI result in the OHM detection fraction being significantly lower than expected for galaxies with LIR >1012 L. The new OHM detections are used to calculate an updated OH luminosity function, with LOH -0.66; this slope is in agreement with previous results. Non-detections of OHMs in the COSMOS field constrain the predicted sky density of OHMs; the results are consistent with a galaxy merger rate evolving as (1+z)m, where 6. Copyright © International Astronomical Union 2012.