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