Water as a powerful probe of energetic interactions
Key Programme: Water In Star-forming regions with Herschel (WISH)
Principal Investigator: Ewine van Dishoeck (Sterrewacht Leiden)
Water has been detected in three young stellar objects observed with PACS during the Herschel Science Demonstration Phase. These are from a sample of almost 90 young stellar objects that will be observed as part of the Water In Star-forming regions with Herschel (WISH) key programme.
WISH will investigate the physical and chemical structure of star forming regions by focussing on the distribution of water and its related species in regions in which new stars are forming. This process takes place deep inside dark clouds and cannot be studied at optical wavelengths. Spectroscopy with HIFI and PACS provide the best diagnostic tools for this type of investigation.
Young stars produce powerful jets during their birth, in a process which is not yet fully understood. In the first PACS observations of L1157 (a low mass young stellar object comparable to our Sun when it was a toddler), the water distribution in the environment of this young protostar clearly traces regions along the jets where shocks deposit energy into the clouds surrounding the protostar.
This is the first water map of such a region and beautifully illustrates the power of PACS to 'light up' the interaction of the young star with its surroundings.
Herbig-Haro 46, a classic example of a low mass young stellar object, was also observed with PACS.
Here, the forbidden excitation lines of [OI] were resolved showing that most of this emission is found along the outflow in the high velocity jets. These [OI] lines, which can only be resolved with Herschel, trace regions of shock-excited gas.
Strong water lines were also detected in NGC 7129 (an intermediate mass young stellar object), along with other related trace lines (OH, CO and [OI]). These new observations challenge the current models describing the environment of this object.
The first preliminary results of this small sample of the WISH objects have clearly demonstrated the power of Herschel to probe these poorly understood regions and the role of water in shaping them.