$Herschel$/PACS OH Spectroscopy of Seyfert, LINER, and Starburst
  Galaxies
  We investigated the 65$\mu$m, 71$\mu$m, 79$\mu$m, 84$\mu$m, 119$\mu$m, and
163$\mu$m OH doublets of 178 local (0 < $z$ < 0.35) galaxies. They were
observed using the $Herschel$/PACS spectrometer, including Seyfert galaxies,
LINERs, and star-forming galaxies. We observe these doublets exclusively in
absorption (OH71), primarily in absorption (OH65, OH84), mostly in emission
(OH79), only in emission (OH163) and an approximately even mix of the both
(OH119). In 19 galaxies we find P-Cygni or reverse P-Cygni line profiles in the
OH doublets. We use several galaxy observables to probe spectral
classification, brightness of a central AGN/starburst component, and radiation
field strength. We find that OH79, OH119, and OH163 are more likely to display
strong emission for bright, unobscured AGN. For less luminous, obscured AGN and
non-active galaxies, we find populations of strong absorption (OH119), weaker
emission (OH163), and a mix of weak emission and weak absorption (OH79). For
OH65, OH71 and OH84, we do not find significant correlations with the
observables listed above. We do find relationships between OH79 and OH119 with
both the 9.7$\mu$m silicate feature and Balmer decrement dust extinction
tracers in which more dust leads to weaker emission / stronger absorption. The
origin of emission for the observed OH doublets, whether from collisional
excitation, or from radiative pumping by infrared photons, is discussed.
