| Description |
H2O and OH are key tracers of the structure, kinematics, and activityin the nuclear regions of (Ultra) Luminous Infrared Galaxies (ULIRGs): with their excitation dominated by pumping by far-infrared continuumradiation, they probe the nuclear source of the far-IR radiation and itsassociated structures (disks, torus); their P-Cygni, absorption, andemission profiles trace massive molecular outflows and possibly inflows, andthe astrophysically important associated energetics involved in the (negative)feedback from star formation and/or AGN on the molecular gas; they probe thephysical and radiative environments (X-rays, cosmic rays, hot cores) wherethey reside. In order to distinguish among the above scenarios, we propose PACS spectroscopy of key transitions of H2O and OH in a sample of 9bright (U)LIRGs where submillimeter H2O lines have been detected with SPIRE,as well as key diagnostic lines of NH3 and OH+ to ascertain the formationmechanism and implied physical processes. The proposed observations will serveas a crucial benchmark for future routine observations of H2O with ALMA in thedistant Universe. |
