Radiation-Hydrodynamic Simulations of Protostellar Outflows: Synthetic Observations and Data Comparisons

TL;DR

This study uses 3D radiation-hydrodynamic simulations to analyze low-mass protostellar outflows, creating synthetic CO observations to compare with real data, revealing effects of resolution, orientation, and measurement methods on inferred properties.

Contribution

It introduces a quantitative method for measuring outflow opening angles and demonstrates their evolution, highlighting the impact of observational biases and gas interactions on outflow property estimates.

Findings

Outflow opening angles broaden over time in simulations and observations.

Significant asymmetry exists between red and blue lobes due to core interactions.

Mass estimates can be significantly underestimated when using velocity cutoffs or optically thick emission.

Abstract

We present results from three-dimensional, self-gravitating, radiation-hydrodynamic simulations of low-mass protostellar outflows. We construct synthetic observations in 12CO in order to compare with observed outflows and evaluate the effects of beam resolution and outflow orientation on inferred outflow properties. To facilitate the comparison, we develop a quantitative prescription for measuring outflow opening angles. Using this prescription, we demonstrate that, in both simulations and synthetic observations, outflow opening angles broaden with time similarly to observed outflows. However, the interaction between the outflowing gas and the turbulent core envelope produces significant asymmetry between the red and blue shifted outflow lobes. We find that applying a velocity cutoff may result in outflow masses that are underestimated by a factor 5 or more, and masses derived from optically thick CO emission further underpredict the mass of the high-velocity gas by a factor of 5-10. Derived excitation temperatures indicate that outflowing gas is hotter than the ambient gas with temperature rising over time, which is in agreement with the simulation gas temperatures. However, excitation temperatures are otherwise not well correlated with the actual gas temperature.