Water comma Molecular Ions comma and a Massive Molecular Outflow in Arp 220

The archetypal ultraluminous infrared galaxy Arp 220 revealed aremarkably rich spectrum in Herschel SPIRE FTS observations, includingluminous emission from warm CO and water. The spectrum also revealedthe presence of a massive molecular outflow, traced by P Cygni lineprofiles in the molecular ions OH+ and H2O+, and possiblyH2O. Comparison of the column densities of these ions relative towater (and the absence of the ion H3O+) indicated that only an XDRpowered by an Xrayluminous AGN is capable of explaining the relativeabundances; that these molecular ions are the same species that areparticipating in the outflow suggests there may be a connectionbetween the AGN and the outflow.Because the FTS did not resolve the lines, only limited informationregarding the outflow and the column densities could be derived fromthe saturated lines. To much more accurately characterize both thephysical and chemical state of the gas (in particular the waterchemistry) and the mass and energetics of the outflow, we propose toobtain HIFI observations of a number of H2O, H2O+, and OH+ emissionand absorption lines (including those exhibiting P Cygni profiles). Inaddition, we propose to observe two fairly strong unidentifiedemission lines, which fall quite close to the expected frequencies ofthe HCN and HCO+ J65 rotation lines. Lowerlying transitions of bothspecies have been measured from the ground; the apparent velocityoffsets from the expected positions may be the consequence of complexemission and/or absorption profiles. In the case of HCN, the FTS datahave established that the J1312 line and above are seen inabsorption. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]