A grid of one-dimensional low-mass star formation collapse models

Abstract

The current study was developed to provide a database of relatively simple numerical simulations of protostellar collapse, as a template library for observations of cores and very young protostars, and for researchers who wish to test their chemical modeling under dynamic astrophysical conditions. It was also designed to identify statistical trends that may appear when running many models of the formation of low-mass stars by varying the initial conditions. 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 8 Msun, temperatures of 5-30 K and radii between 3000 and 30,000 AU. A spread in the thermal evolutionary tracks of the runs was found, due to differing initial conditions and optical depths. Within less than an order of magnitude, all first and second Larson cores had masses and radii independent of the initial conditions. 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 3 Mjup and 8 Rjup, 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, along different isentropes, but each story line can largely be predicted by the initial conditions. All the data from the simulations are publicly available at this address: http://starformation.hpc.ku.dk/grid-of-protostars.