Star-forming gas in young clusters

TL;DR

This paper estimates initial conditions for star formation in young clusters, revealing that protostellar infall and accretion properties differ from isolated star formation, with implications for observed densities and luminosities.

Contribution

It provides a model for initial gas conditions in cluster-forming regions, incorporating feedback-driven infall stopping and matching observed densities and luminosities.

Findings

Infall duration increases with protostar mass from 0.01 to 0.3 Myr.

Typical accretion luminosity is around 5 solar luminosities.

Initial conditions are denser and warmer than isolated star formation environments.

Abstract

Initial conditions for star formation in clusters are estimated for protostars whose masses follow the initial mass function (IMF) from 0.05 to 10 solar masses. Star-forming infall is assumed equally likely to stop at any moment, due to gas dispersal dominated by stellar feedback. For spherical infall, the typical initial condensation must have a steep density gradient, as in low-mass cores, surrounded by a shallower gradient, as in the clumps around cores. These properties match observed column densities in cluster-forming regions when the mean infall stopping time is 0.05 Myr and the accretion efficiency is 0.5. The infall duration increases with final protostar mass, from 0.01 to 0.3 Myr, and the mass accretion rate increases from 3 to 300 x 10^(-6) solar masses/yr. The typical spherical accretion luminosity is ~5 solar luminosities, reducing the luminosity problem to a factor ~3. The initial condensation density gradient changes from steep to shallow at radius 0.04 pc, enclosing 0.9 solar masses, with mean column density 2 x 10^(22) cm^(-2), and with effective central temperature 16 K. These initial conditions are denser and warmer than those for isolated star formation.