Disk Masses at the end of the main accretion phase: CARMA Observations and Multi-Wavelength Modeling of Class I Protostars

TL;DR

This study uses CARMA millimeter observations combined with multi-wavelength data to estimate the disk masses of Class I protostars, revealing they are higher than in more evolved stars but still insufficient for giant planet formation.

Contribution

First detailed multi-wavelength modeling of Class I protostellar disks to constrain their masses and structures, highlighting differences from more evolved star systems.

Findings

Disk masses range from <0.01 to >0.1 Msun.

Class I disks have higher masses than Class II but are still too low for giant planet formation.

Substantial particle growth may hide disk mass in larger bodies.

Abstract

We present imaging observations at 1.3 mm wavelength of Class I protostars in the Taurus star forming region, obtained with the CARMA interferometer. Of an initial sample of 10 objects, we detected and imaged millimeter wavelength emission from 9. One of the 9 is resolved into two sources, and detailed analysis of this binary protostellar system is deferred to a future paper. For the remaining 8 objects, we use the CARMA data to determine the basic morphology of the millimeter emission. Combining the millimeter data with 0.9 micron images of scattered light, Spitzer IRS spectra, and broadband SEDs (all from the literature), we attempt to determine the structure of the circumstellar material. We consider models including both circumstellar disks and envelopes, and constrain the masses (and other structural parameters) of each of these components. We show that the disk masses in our sample span a range from <0.01 to >0.1 Msun. The disk masses for our sample are significantly higher than for samples of more evolved Class II objects. Thus, Class I disk masses probably provide a more accurate estimate of the initial mass budget for star and planet formation. However, the disk masses determined here are lower than required by theories of giant planet formation. The masses also appear too low for gravitational instability, which could lead to high mass accretion rates. Even in these Class I disks, substantial particle growth may have hidden much of the disk mass in hard-to-see larger bodies.