The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars VI. Insights from Radiative Transfer Modeling

TL;DR

This study uses radiative transfer modeling on ALMA and VLA data of 97 Orion protostars to analyze disk properties, revealing small, stable disks with no clear evolutionary trend in dust mass, and highlighting the importance of magnetic effects.

Contribution

It provides the first comprehensive radiative transfer analysis of a large protostellar sample in Orion, offering new insights into disk sizes, masses, and stability across different protostellar classes.

Findings

Disks are small with median dust radius ~29 au.

No significant difference in properties between Class 0, I, and Flat Spectrum sources.

Disks are broadly gravitationally stable.

Abstract

We present Markov Chain Monte Carlo radiative transfer modeling of a joint ALMA 345 GHz and spectral energy distribution dataset for a sample of 97 protostellar disks from the VLA and ALMA Nascent Disk and Multiplicity Survey of Orion Protostars. From this modeling, we derive disk and envelope properties for each protostar, allowing us to examine the bulk properties of a population of young protostars. We find that disks are small, with a median dust radius of $ 29.4^{+ 4.1}_{- 2.7}$ au and a median dust mass of $ 5.8^{+ 4.6}_{- 2.7}$ M$_{\oplus}$. We find no statistically significant difference between most properties of Class 0, I, and Flat Spectrum sources with the exception of envelope dust mass and inclination. The distinction between inclination is an indication that the Class 0/I/Flat Spectrum system may be difficult to tie uniquely to the evolutionary state of protostars. When comparing with Class II disk dust masses in Taurus from similar radiative transfer modeling, we further find that the trend of disk dust mass decreasing from Class 0 to Class II disks is no longer present, though it remains unclear whether such a comparison is fair due to differences in star forming region and modeling techniques. Moreover, the disks we model are broadly gravitationally stable. Finally, we compare disk masses and radii with simulations of disk formation and find that magnetohydrodynamical effects may be important for reproducing the observed properties of disks.