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<z<1.5, making this is the first large, systematic search for OHMs at z>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.
|Original language||English (US)|
|Title of host publication||Cosmic Masers - from OH to H0|
|Editors||Roy S. Booth, Elizabeth M. L. Humphreys, Wouter H.T. Vlemmings|
|Number of pages||5|
|State||Published - Jul 2012|
|Name||Proceedings of the International Astronomical Union|
Bibliographical noteFunding Information:
This work was part of the Ph.D. thesis of KWW at the University of Colorado, and will be submitted in early 2012 as Willett, Darling, Kent, & Braatz (2012). Observations were funded in part by student support grants from NRAO. We are indebted to the staff of the Green Bank Telescope, whose expertise and assistance made these observations possible. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
- galaxies: interactions
- infrared: galaxies
- radio lines: galaxies