Do tides play a role in the determination of the pre-stellar core mass function?

TL;DR

This study investigates the influence of tidal forces on the collapse of density perturbations in pre-stellar cores, concluding that tides have a limited effect on star formation and the initial mass function.

Contribution

The paper introduces a tensorial virial approach to assess tidal effects on core collapse, accounting for anisotropy and dynamical factors, which refines previous models.

Findings

Tides only slightly increase the collapse threshold for low-mass perturbations.

Tides are unlikely to significantly influence the characteristic mass of the IMF.

A new collapse condition considering anisotropic tidal effects is proposed.

Abstract

Recent studies have examined the role of tides in the star formation process. They suggest, notably, that the tides determine the characteristic mass of the stellar initial mass function (IMF) by preventing the collapse of density fluctuations that would become gravitationally unstable in the absence of the tidal field generated by a neighboring central mass. However, most of these studies consider the tidal collapse condition as a 1D process or use a scalar virial condition and thus neglect the anisotropy of the tidal field and its compressive effects. In the present paper, we consider a turbulence-induced density perturbation formed in the envelope of a central core. This perturbation is subject to a tidal field generated by the central core. We study its evolution taking dynamical effects and the anisotropy of the tides into account. Based on the general tensorial virial equations, we determine a new collapse condition that takes these mechanisms into account. We identify two regimes: (i) a weak tidal regime in which the dynamics of the perturbation is only slightly modified by the action of the tides and (ii) a strong tidal regime in which the density threshold for collapse can potentially be increased due to the combined effects of the tides and the rotational support generated by the tidal synchronization of the perturbation with the orbital motion. In the case of a turbulence-induced density perturbation formed in the vicinity of a first Larson core, we show that the density threshold above which the perturbation collapses is increased only for low-mass perturbations (less than 2.7 solar mass) and only by at most a factor of 1.5. We conclude that tides likely do not play a major role in the process of star formation or in the determination of the characteristic mass of the IMF. We propose an alternative explanation for the observed value of the characteristic mass of the IMF.