Molecular Line Emission from Massive Protostellar Disks: Predictions for ALMA and the EVLA

TL;DR

This paper predicts molecular line emissions from massive protostellar disks using simulations, demonstrating that next-generation telescopes like ALMA and EVLA can detect and analyze their structure, rotation, and instabilities.

Contribution

It provides detailed predictions for molecular line emissions from massive protostellar disks based on radiation-hydrodynamic simulations, aiding future observational studies.

Findings

Disks show brightness temperatures of hundreds of Kelvin.

Telescopes like ALMA and EVLA can detect disks and measure rotation curves.

Disks exhibit sub-structure, non-axisymmetry, and velocity offsets due to gravitational instability.

Abstract

We compute the molecular line emission of massive protostellar disks by solving the equation of radiative transfer through the cores and disks produced by the recent radiation-hydrodynamic simulations of Krumholz, Klein, & McKee. We find that in several representative lines the disks show brightness temperatures of hundreds of Kelvin over velocity channels ~10 km s^-1 wide, extending over regions hundreds of AU in size. We process the computed intensities to model the performance of next-generation radio and submillimeter telescopes. Our calculations show that observations using facilities such as the EVLA and ALMA should be able to detect massive protostellar disks and measure their rotation curves, at least in the nearest massive star-forming regions. They should also detect significant sub-structure and non-axisymmetry in the disks, and in some cases may be able to detect star-disk velocity offsets of a few km s^-1, both of which are the result of strong gravitational instability in massive disks. We use our simulations to explore the strengths and weaknesses of different observational techniques, and we also discuss how observations of massive protostellar disks may be used to distinguish between alternative models of massive star formation.