A discontinuity in the low-mass IMF - the case of high multiplicity

TL;DR

This paper investigates how high multiplicity of brown dwarfs affects the initial mass function's discontinuity, finding that the discontinuity persists even with a BD binary fraction as high as 60%, and that the BD IMF remains consistent across different star-forming regions.

Contribution

It demonstrates that the IMF discontinuity in the low-mass regime persists despite high brown dwarf multiplicity, challenging previous assumptions about the IMF's shape.

Findings

Discontinuity remains even with 60% BD binary fraction.

No variation of BD IMF across different star-forming regions.

BDs form about two per 10 low-mass stars with a power-law index of +0.3.

Abstract

The empirical binary properties of brown dwarfs (BDs) differ from those of normal stars suggesting BDs form a separate population. Recent work by Thies & Kroupa revealed a discontinuity of the initial mass function (IMF) in the very-low-mass star regime under the assumption of a low multiplicity of BDs of about 15 per cent. However, previous observations had suggested that the multiplicity of BDs may be significantly higher, up to 45 per cent. This contribution investigates the implication of a high BD multiplicity on the appearance of the IMF for the Orion Nebula Cluster, Taurus-Auriga, IC 348 and the Pleiades. We show that the discontinuity remains pronounced even if the observed MF appears to be continuous, even for a BD binary fraction as high as 60%. We find no evidence for a variation of the BD IMF with star-forming conditions. The BD IMF has a power-law index alpha = +0.3 and about two BDs form per 10 low-mass stars assuming equal-mass pairing of BDs.