Transit Flow Models for Low‐ and High‐Mass Protostars

Abstract

In this work, the gas infall and the formation of outflows around low- and high-mass protostars are investigated. A radial self-similar approach to model the transit of the molecular gas around the central object is employed. We include gravitational and radiative fields to produce heated pressure-driven outflows with magnetocentrifugal acceleration and collimation. Outflow solutions with negligible or vanishing magnetic fields are reported. They indicate that thermodynamics is a sufficient engine to generate an outflow. The magnetized solutions show dynamically significant differences in the axial region, precisely where the radial velocity and collimation are the largest. They compare quantitatively well with observations. The influence of the opacity on the transit solutions is also studied. It is found that, when dust is not the dominant coolant, such as in the primordial universe, mass infall rates have substantial larger values in the equatorial region. This suggests that stars forming in a dust-free environment should be able to accrete much more mass and become more massive than present-day protostars. It is also suggested that molecular outflows may be dominated by the global transit of material around the protostar during the very early stages of star formation, especially in the case of massive or dust-free star formation. © 2006. The American Astronomical Society. All rights reserved.