Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud

TL;DR

This study measures the masses of disks around early-stage Class I protostars in Taurus, revealing they are initially more massive than later stages, with significant dust grain growth occurring early in star formation.

Contribution

First measurement of disk masses for Class I protostars in Taurus using radiative transfer modeling and multi-wavelength data, highlighting early dust processing.

Findings

Median disk mass is 0.018 M_sun, higher than Class II disks.

Dust grains grow by a factor of 75 by the Class II stage.

Dust processing begins during the Class I stage.

Abstract

Class I protostars are thought to represent an early stage in the lifetime of protoplanetary disks, when they are still embedded in their natal envelope. Here we measure the disk masses of 10 Class I protostars in the Taurus Molecular Cloud to constrain the initial mass budget for forming planets in disks. We use radiative transfer modeling to produce synthetic protostar observations and fit the models to a multi-wavelength dataset using a Markov Chain Monte Carlo fitting procedure. We fit these models simultaneously to our new CARMA 1.3 mm observations that are sensitive to the wide range of spatial scales that are expected from protostellar disks and envelopes so as to be able to distinguish each component, as well as broadband spectral energy distributions compiled from the literature. We find a median disk mass of 0.018 M$_{\odot}$ on average, more massive than the Taurus Class II disks, which have median disk mass of $\sim$0.0025 M$_{\odot}$. This decrease in disk mass can be explained if dust grains have grown by a factor of 75 in grain size, indicating that by the Class II stage, at a few Myr, a significant amount of dust grain processing has occurred. However, there is evidence that significant dust processing has occurred even during the Class I stage, so it is likely that the initial mass budget is higher than the value quoted here.