Helium preenrichment in the star-forming regions

TL;DR

This paper proposes that element diffusion in star-forming clouds can cause significant helium abundance variations, potentially explaining observed anomalies in globular clusters.

Contribution

It introduces a mechanism where helium diffusion in neutral gas clouds leads to initial abundance fluctuations, addressing discrepancies in globular cluster observations.

Findings

Helium diffusion timescales can be less than 10^8 years in certain clouds.

Diffusion can produce large helium abundance fluctuations.

Explains observed helium inhomogeneities in globular clusters.

Abstract

We show that element diffusion can produce large fluctuations in the initial helium abundance of the star-forming clouds. Diffusion time-scale, which in stars is much larger than the Hubble time, can fall below 10^8 years in the neutral gas clouds dominated by collisionless dark matter or with dynamically important radiation or magnetic pressure. Helium diffusion may therefore explain the recent observations of globular clusters, which are inconsistent with initially homogeneous helium distribution.