A grid of 1D low-mass star formation models

A large set of 143 calculations of the gravitational collapse of an isolated sphere of gas with uniform temperature and a Bonnor-Ebert-like density profile was undertaken using a 1D fully implicit Lagrangian radiation hydrodynamics code. The parameter space covered initial masses from 0.2 to 8M_{sun}_, temperatures of 5-30K, and radii 3000-30,000AU. A spread due to differing initial conditions and optical depths, was found in the thermal evolutionary tracks of the runs.

Within less than an order of magnitude, all first and second Larson cores had masses and radii essentially independent of the initial conditions. Radial profiles of the gas density, velocity, and temperature were found to vary much more outside of the first core than inside. The time elapsed between the formation of the first and second cores was found to strongly depend on the first core mass accretion rate, and no first core in our grid of models lived for longer than 2000 years before the onset of the second collapse.

The end product of a protostellar cloud collapse, the second Larson core, is at birth a canonical object with a mass and radius of about 3M_jup_ and 8R_jup_, independent of its initial conditions. The evolution sequence which brings the gas to stellar densities can, however, proceed in a variety of scenarios, on different timescales or along different isentropes, but each story line can largely be predicted by the initial conditions.