Global Models for the Evolution of Embedded, Accreting Protostellar Disks

TL;DR

This paper introduces a simple one-zone model for embedded, accreting protostellar disks, predicting their properties and evolution across different stellar masses, with implications for disk fragmentation, binary formation, and spiral structures.

Contribution

It presents a novel, self-consistent model incorporating temperature and angular momentum transport mechanisms to study early protostellar disk evolution.

Findings

Gravitational instabilities dominate angular momentum transport in stars >1 solar mass.

Disk fragmentation and binary formation increase with stellar mass.

Predicted disk properties will be testable by future surveys.

Abstract

Most analytic work to date on protostellar disks has focused on those in isolation from their environments. However, observations are now beginning to probe the earliest, most embedded phases of star formation, during which disks are rapidly accreting from their parent cores and cannot be modeled in isolation. We present a simple, one-zone model of protostellar accretion disks with high mass infall rates. Our model combines a self-consistent calculation of disk temperatures with an approximate treatment of angular momentum transport via two mechanisms. We use this model to survey the properties of protostellar disks across a wide range of stellar masses and evolutionary times, and make predictions for disks' masses, sizes, spiral structure, and fragmentation that will be directly testable by future large-scale surveys of deeply embedded disks. We define a dimensionless accretion-rotation parameter which, in conjunction with the disk's temperature, controls the disk evolution. We track the dominant mode of angular momentum transport, and demonstrate that for stars with final masses greater than roughly one solar mass, gravitational instabilities are the most important mechanism as most of the mass accumulates. We predict that binary formation through disk fission, fragmentation of the disk into small objects, and spiral arm strength all increase in importance to higher stellar masses.