Environmental Effects of Star-Forming Cores on Mass Accretion Rate

TL;DR

This study models how the environment surrounding star-forming cores influences the rate at which protostars accumulate mass, revealing that external gas inflow from dense envelopes can significantly boost protostellar growth.

Contribution

It introduces simulations of core evolution considering environmental effects, highlighting the role of outer envelope density in mass accretion rates, which was not previously emphasized.

Findings

Mass accretion rate decreases with core depletion in low-density environments.

High-density envelopes temporarily enhance accretion rates.

External gas inflow significantly contributes to protostellar mass growth.

Abstract

We calculate the evolution of cloud cores embedded in different envelopes to investigate environmental effects on the mass accretion rate onto protostars. As the initial state, we neglect the magnetic field and cloud rotation, and adopt star-forming cores composed of two parts: a centrally condensed core and an outer envelope. The inner core has a critical Bonnor-Ebert density profile and is enclosed by the outer envelope. We prepare 15 star-forming cores with different outer envelope densities and gravitational radii, within which the gas flows into the collapsing core, and calculate their evolution until $\sim 2 \times10^5$ yr after protostar formation. The mass accretion rate decreases as the core is depleted when the outer envelope density is low. In contrast, the mass accretion rate is temporarily enhanced when the outer envelope density is high and the resultant protostellar mass exceeds the initial mass of the centrally condensed core. Some recent observations indicate that the mass of prestellar cores is too small to reproduce the stellar mass distribution. Our simulations show that the mass inflow from outside the core contributes greatly to protostellar mass growth when the core is embedded in a high-density envelope, which could explain the recent observations.