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Published February 11, 2015 | Submitted + Published
Journal Article Open

Observations of hydroxyl in early-type galaxies

Abstract

We used Arecibo Observatory and the Green Bank Telescope to observe OH in twelve early type galaxies with known reservoirs of dense gas. We present three new detections of OH in absorption in the 1667 MHz line. One objective of our survey was to find evidence of molecular outflows, but our sensitivity, and the strength of the OH absorption, were insufficient to detect outflows. The detected sources have infrared luminosities and dust temperatures among the lowest of any galaxy detected in OH absorption. The ratio L_(HCN)=L_(CO), a measure of the dense gas fraction in galaxies, is a powerful selector of OH megamasers for galaxies with high infrared luminosity. In early-type galaxies, which have much lower infrared luminosities, L_(HCN)=L_(CO) is also a promising tool for discovering OH, but in absorption rather than in maser emission. In addition to dense molecular gas, a radio continuum source and a favorable line-of-sight to the observer are likely key factors in detecting OH absorbers.

Additional Information

© 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2014 November 19. Received 2014 November 18; in original form 2014 September 8. First published online December 16, 2014. We are grateful to the referee for thoughtful comments that improved the content and clarity of the paper. We thank Andrew Siemion for assistance observing remotely with the GBT, and Carl Heiles and Leo Blitz for useful discussions. JM received support from a National Science Foundation Graduate Research Fellowship. KA is supported by funding through Herschel, a European Space Agency Cornerstone Mission with significant participation by NASA, through an award issued by JPL/Caltech. This research used NASA Astrophysics Data System Bibliographic Services, the SIMBAD data base, operated at CDS, Strasbourg, France, and the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.

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Published - MNRAS-2015-McBride-392-9.pdf

Submitted - 1411.7409v1.pdf

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