Disk Wind Feedback from High-mass Protostars. III. Synthetic CO Line Emission

TL;DR

This study uses synthetic CO line emission from MHD simulations of massive protostars to evaluate observational estimates of outflow properties and compare them with theoretical models, aiding interpretation of ALMA data.

Contribution

It introduces a detailed method for generating synthetic CO emission from simulations and assesses the accuracy of observationally derived outflow parameters.

Findings

Mass and momentum estimates can be uncertain by up to a factor of four.

Kinetic energy is significantly underestimated from molecular line observations.

Synthetic spectra can effectively match observed protostars, constraining their properties.

Abstract

To test theoretical models of massive star formation it is important to compare their predictions with observed systems. To this end, we conduct CO molecular line radiative transfer post-processing of 3D magneto-hydrodynamic (MHD) simulations of various stages in the evolutionary sequence of a massive protostellar core, including its infall envelope and disk wind outflow. Synthetic position-position-velocity (PPV) cubes of various transitions of CO, 13CO, and C18O emission are generated. We also carry out simulated Atacama Large Millimeter/submillimeter Array (ALMA) observations of this emission. We compare the mass, momentum and kinetic energy estimates obtained from molecular lines to the true values, finding that the mass and momentum estimates can have uncertainties of up to a factor of four. However, the kinetic energy estimated from molecular lines is more significantly underestimated. Additionally, we compare the mass outflow rate and momentum outflow rate obtained from the synthetic spectra with the true values. Finally, we compare the synthetic spectra with real examples of ALMA-observed protostars and determine the best fitting protostellar masses and outflow inclination angles. We then calculate the mass outflow rate and momentum outflow rate for these sources, finding that both rates agree with theoretical protostellar evolutionary tracks.