Physical properties of outflows: Comparing CO and H2O based parameters in Class 0 sources

TL;DR

This study compares physical outflow parameters derived from CO and H2O tracers in Class 0 sources, finding consistent results within a factor of a few, thus validating the use of different molecular tracers in outflow analysis.

Contribution

It provides a direct comparison of outflow properties derived from CO and H2O, demonstrating their consistency and validating the use of multiple tracers in outflow studies.

Findings

Outflow parameters from CO and H2O are spatially co-located.

Flow widths are comparable when using both tracers.

Momentum rate and luminosity estimates agree within a factor of 4 and 3, respectively.

Abstract

Context. The observed physical properties of outflows from low-mass sources put constraints on possible ejection mechanisms. Historically, these quantities have been derived from CO using ground-based observations. It is thus important to investigate whether parameters such as momentum rate (thrust) and mechanical luminosity (power) are the same when different molecular tracers are used. Aims. We aim at determining the outflow momentum, dynamical time-scale, thrust, energy and power using CO and H2O as tracers of outflow activity. Methods. Within the framework of the WISH key program, three molecular outflows from Class 0 sources have been mapped using the HIFI instrument aboard Herschel. We use these observations together with previously published H2 data to infer the physical properties of the outflows. We compare the physical properties derived here with previous estimates based on CO observations. Results. Inspection of the spatial distribution of H2O and H2 confirms that these molecules are co-spatial. The most prominent emission peaks in H2 coincide with strong H2O emission peaks and the estimated widths of the flows when using the two tracers are comparable. Conclusions. For the momentum rate and the mechanical luminosity, inferred values are independent of which tracer that is used, i.e., the values agree to within a factor of 4 and 3 respectively.