Environmental effects of star-forming cores on mass accretion rate

We calculate the evolution of cloud cores embedded in different envelopes to investigate environmental effects on the mass accretion rate on to 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 similar to 2 x 10(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 pre-stellar 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.

Automated summary

We calculated the evolution of cloud cores embedded in different envelopes to study the effects of the environment on the mass accretion rate onto protostars. The simulations showed that the mass accretion rate decreases when the outer envelope density is low, but temporarily increases when the outer envelope density is high and the protostellar mass exceeds the initial mass of the core. These findings could explain recent observations that suggest the mass of pre-stellar cores is too small to reproduce the stellar mass distribution.