Signatures of Rapidly Rotating Stars with Chemically Homogeneous Evolution in the First Galaxies

TL;DR

This paper explores how rapidly rotating stars undergoing chemically homogeneous evolution can explain the unexpectedly high UV luminosity of early galaxies observed by JWST, suggesting a significant role for CHE in early galaxy formation.

Contribution

It demonstrates that CHE stars can boost galaxy UV luminosity, helping reconcile observations with galaxy formation models, a novel application of CHE in early universe studies.

Findings

CHE stars increase UV luminosity by a factor of 3-6.

Reproduces high-redshift UV luminosity functions with less extreme star formation parameters.

Highlights CHE's importance in early galaxy evolution and related phenomena.

Abstract

The James Webb Space Telescope (JWST) has revealed an unexpectedly high abundance of UV luminous galaxies at redshifts $z\gtrsim 10$, challenging `standard' galaxy formation models. This study investigates the role of rapidly rotating (massive) stars undergoing chemically homogeneous evolution (CHE) in reconciling this potential tension. These stars are more compact, hotter, and exhibit enhanced UV emission. We find that the rest-frame UV luminosity of star-forming galaxies can be significantly enhanced by a factor of $\sim 3-6$ when CHE stars above a minimum initial mass of $m_{\star,\min}^{\rm CHE}\sim 2-10\ \rm M_\odot$ account for more than half of the total stellar mass following a Salpeter initial mass function. As a result, the UV luminosity functions observed at $z\sim 12-16$ can be reproduced with less extreme values of star formation efficiency and UV luminosity stochastic variability. Our results highlight the potential of CHE in explaining the UV-bright galaxy populations detected by JWST and call for future work to explore the broader astrophysical implications of CHE and its associated phenomena in the early universe, such as gamma-ray bursts, compact object binaries, and metal enrichment.