Massive star feedback - from the first stars to the present

TL;DR

This paper reviews how mass loss in massive stars depends on metallicity and highlights overlooked physics that could significantly increase mass-loss rates in the early universe, impacting cosmic reionization and chemical enrichment.

Contribution

It introduces new considerations for mass-loss predictions in massive stars near the Eddington limit and with enriched atmospheres, crucial for understanding early cosmic evolution.

Findings

Mass-loss rates decrease steeply with lower metallicity (Z^{0.7-0.85}).

Stars near the Eddington limit may have enhanced mass loss.

Primarily enriched atmospheres can significantly boost mass-loss rates.

Abstract

The amount of mass loss is of fundamental importance to the lives and deaths of very massive stars, the input of chemical elements and momentum into the interstellar and intergalactic media, as well as the emitted ionizing radiation. I review mass-loss predictions for hot massive stars as a function of metal content for groups of OB stars, Luminous Blue Variables, and Wolf-Rayet stars. Although it is found that the predicted mass-loss rates drop steeply with decreasing metal content (Mdot ~ Z^{0.7-0.85}), I highlight two pieces of physics that are often overlooked: (i) mass-loss predictions for massive stars approaching the Eddington limit, and for (ii) stars that have enriched their own atmospheres with primary elements such as carbon. Both of these effects may significantly boost the mass-loss rates of the first stars - relevant for the reionization of the Universe, and a potential pre-enrichment of the intergalactic medium - prior to the first supernova explosions.