H2O spectra of 29 nearby Class 0/I protostars

Abstract

Outflows are an important part of the star formation process as both the result of ongoing active accretion and one of the main sources of mechanical feedback on small scales. Water is the ideal tracer of these effects because it is present in high abundance for the conditions expected in various parts of the protostar, particularly the outflow. We constrain and quantify the physical conditions probed by water in the outflow-jet system for Class 0 and I sources. We present velocity-resolved Herschel HIFI spectra of multiple water-transitions observed towards 29 nearby Class 0/I protostars as part of the WISH guaranteed time key programme. The lines are decomposed into different Gaussian components, with each component related to one of three parts of the protostellar system; quiescent envelope, cavity shock and spot shocks in the jet and at the base of the outflow. We then use non-LTE radex models to constrain the excitation conditions present in the two outflow-related components. This sample was the target of a series of observations of gas-phase water transitions with the Heterodyne Instrument for the Far-Infrared (HIFI) on Herschel between March 2010 and October 2011. Three of the Class I sources (IRAS3A, RCrA-IRS5A and HH100-IRS) were only observed in the 557GHz H2O 110-101 line, which was presented for all sources by Kristensen et al. All other sources were observed in between four and seven H216O transitions and between one and four H218O transitions. Additional data from two OT2 programmes, OT2rvisser2 and OT2evandish4, are also included to augment the WISH data.