We have investigated the water abundance in shock-heated molecular gas , making use of Herschel measurements of far-infrared CO and H _ { 2 } O line emissions in combination with Spitzer measurements of mid-IR H _ { 2 } rotational emissions .
We present far-infrared line spectra obtained with Herschel ’ s PACS instrument in range spectroscopy mode towards two positions in the protostellar outflow NGC 2071 and one position each in the supernova remnants W28 and 3C391 .
These spectra provide unequivocal detections , at one or more positions , of 12 rotational lines of water , 14 rotational lines of CO , 8 rotational lines of OH ( 4 lambda doublets ) , and 7 fine-structure transitions of atoms or atomic ions .
We first used a simultaneous fit to the CO line fluxes , along with H _ { 2 } rotational line fluxes measured previously by Spitzer , to constrain the temperature and density distribution within the emitting gas ; and we then investigated the water abundances implied by the observed H _ { 2 } O line fluxes .
The water line fluxes are in acceptable agreement with standard theoretical models for nondissociative shocks that predict the complete vaporization of grain mantles in shocks of velocity v \sim 25 km/s , behind which the characteristic gas temperature is \sim 1300 K and the H _ { 2 } O/CO ratio is 1.2