The observable prestellar phase of the IMF

TL;DR

This paper investigates the relationship between prestellar core mass functions and the stellar initial mass function, revealing differences in core and star masses, and providing insights into star formation efficiency and brown dwarf progenitors.

Contribution

It demonstrates that the prestellar core mass function differs from the IMF and proposes a method to estimate star formation efficiency using core selection criteria.

Findings

Prestellar core masses are smaller than resulting stellar system masses.

The CMF shows a slope change around 3-5 solar masses.

Selecting cores above half their Bonnor-Ebert mass aligns the CMF with the IMF.

Abstract

The observed similarities between the mass function of prestellar cores (CMF) and the stellar initial mass function (IMF) have led to the suggestion that the IMF is already largely determined in the gas phase. However, theoretical arguments show that the CMF may differ significantly from the IMF. In this Letter, we study the relation between the CMF and the IMF, as predicted by the IMF model of Padoan and Nordlund. We show that 1) the observed mass of prestellar cores is on average a few times smaller than that of the stellar systems they generate; 2) the CMF rises monotonically with decreasing mass, with a noticeable change in slope at approximately 3-5 solar masses, depending on mean density; 3) the selection of cores with masses larger than half their Bonnor-Ebert mass yields a CMF approximately consistent with the system IMF, rescaled in mass by the same factor as our model IMF, and therefore suitable to estimate the local efficiency of star formation, and to study the dependence of the IMF peak on cloud properties; 4) only one in five pre-brown-dwarf core candidates is a true progenitor to a brown dwarf.