Water emission from the high-mass star-forming region IRAS 17233-3606. High water abundances at high velocities

TL;DR

This study uses Herschel observations and shock modeling to analyze water emission in a high-mass star-forming region, revealing high water abundance and consistent shock conditions in outflows.

Contribution

It presents the first combined modeling of water and SiO emission in a high-mass protostellar outflow using Herschel data.

Findings

Water abundance in outflows is similar to low-mass star-forming regions.

A single shock model explains both water and SiO emissions.

Estimated water mass in the outflow is approximately 12.5 Earth masses.

Abstract

We investigate the physical and chemical processes at work during the formation of a massive protostar based on the observation of water in an outflow from a very young object previously detected in H2 and SiO in the IRAS 17233-3606 region. We estimated the abundance of water to understand its chemistry, and to constrain the mass of the emitting outflow. We present new observations of shocked water obtained with the HIFI receiver onboard Herschel. We detected water at high velocities in a range similar to SiO. We self-consistently fitted these observations along with previous SiO data through a state-of-the-art, one-dimensional, stationary C-shock model. We found that a single model can explain the SiO and H2O emission in the red and blue wings of the spectra. Remarkably, one common area, similar to that found for H2 emission, fits both the SiO and H2O emission regions. This shock model subsequently allowed us to assess the shocked water column density, N(H2O)=1.2x10^{18} cm^{-2}, mass, M(H2O)=12.5 M_earth, and its maximum fractional abundance with respect to the total density, x(H2O)=1.4x10^{-4}. The corresponding water abundance in fractional column density units ranges between 2.5x10^{-5} and 1.2x10^{-5}, in agreement with recent results obtained in outflows from low- and high-mass young stellar objects.