Water in molecular outflows and shocks: Studies with Odin and Herschel

University dissertation from Chalmers University of Technology

Abstract: This thesis describes observations and analyses of water in molecular outflows from young stellar objects. The abundance of this molecule (with respect to molecular hy- drogen) is deduced from observations carried out with primarily the Odin and Herschel telescopes. The large spatial extents of molecular outflows allow for mapping obser- vations to be done with both facilities, but in addition to this, spectroscopy also allow for the investigation of the kinematics. The observations discussed in this thesis were acquired over the years 2002 to 2011. In the first appended research paper, observations of 15 different shocked regions are reported. The targets were primarily molecular outflows, but two supernova rem- nants were also observed. This study shows that the water abundance in the gas is elevated in the presence of shock waves. Furthermore, the water abundance seems to correlate with the maximum velocity of the shocked gas. In the second paper, previously published observations of the Herbig-Haro object HH 54 are followed up, using APEX, Odin and Herschel. In this work we investigate the relative cooling contribution from CO and H2O and we compare the results with most recent shock models. CO dominates the cooling and we conclude that planar shock models do not explain the observations satisfactorily. Instead we find that a curved geometry can completely account for the observed line profile shapes in the two species. The inferred water abundance is lower than what was previously expected. In the third paper, Herschel mapping observations of VLA 1623 are presented. The ground-state transitions of o-H2O were mapped using the HIFI and PACS instruments but also higher energy transitions were observed towards selected positions in the out- flow lobes. The observed H2O(110 −101) line profiles show a variety of shapes over the observed region and also from this work, we conclude that the water abundance is lower than expected. In addition to this, it is now clear that the regions responsible for the emission in water are warmer than the regions traced by CO. A comparison with H2 data obtained with Spitzer allows us to estimate the physical parameters of the flow. This leads us to conclude, that it does not matter which molecular tracer we use when we infer the force and the power of the VLA 1623 outflow. The analysis is followed up in a letter where we include also the L 1448 and L 1157 outflows.