| Description |
Water is a key molecule for determining the physical and chemicalstructure of star-forming regions because of its large abundancevariations --both in the gas and in the ice-- between warm and coldregions. In this HIFI-led Key Program, we propose a comprehensive setof water observations toward a large sample of well-characterizedprotostars, covering a wide range of masses and luminosities -- from thelowest to the highest mass protostars -- and a large range ofevolutionary stages -- from the first stages represented by thepre-stellar cores to the last stages represented by the pre-mainsequence stars surrounded only by their protostellar disks. Lines ofH2O, H218O, H217O and chemically related hydrideswill be observed. In addition, selected high-frequency lines of COisotopes, O I as well as dust continuum maps will be obtained withHIFI and PACS, and will be complemented by ground-based HDO, CO andcontinuum maps to ensure a self-consistent data set for analysis.Limited mapping information on arcmin scale provides information onlocal variations due to outflows and clustered starformation. Together, the data will elucidate the physical processesresponsible for the warm gas, probe dynamical processes associatedwith forming stars and planets, reveal the chemical evolution of waterand the oxygen-reservoir, and test basic gas-grain chemicalinteractions. They will form an unique legacy for the community as acomplement to future ground-based programs and for planning futurespace missions. |
