| Description |
Water, as a dominant form of oxygen, the most abundant element in the universe after H and He, controls the chemistry of many otherspecies. It is a unique diagnostic of warm gas and energetic processestaking place during star formation.We therefore propose to exploit the unique opportunity of Herschel to study water in large, statistically significant, flux limited samples of massivestar forming regions detected in the recently completed ATLASGAL submm dust continuum survey of the inner Galactic plane.In the last years, our view of massive star forming regions hasdramatically changed by Galactic plane surveys covering cmto IR wavelengths. These surveys enable us for the first time tostudy ALL evolutionary stages of massive star formation (MSF) in anunbiased way. Water, acting as a natural filter for warm, dense gas, allows to probe the chemical and physical conditions in all of these stages close to where the massive stars are forming or just have been formed.ATLASGAL observed submm dust continuum emission as best tracer of the earliest phases of MSF since it is directly probingthe material from which the stars form. As a large unbiased surveyit provide the statistical base to study the scarce and short-livingprotoclusters as the origin of the massive stars and the richestclusters in the Galaxy and supplies us with a legacy value sampleof MSF regions for the water follow ups.Water is typically seen with strongly increasedabundances in broad line wings, providing a new, sensitive probe ofshocked outflowing gas. In addition, the envelope is probed in acombination of absorption and emission with a clear jump inabundance in the warm inner regions close to the forming massivestars. Only Herschel can provide a water survey of a large sample of ATLASGAL selected sources to study water through the evolution of massive star forming regions with a statistically significant sample size. |
