Signatures of Rapidly Rotating Stars with Chemically Homogeneous Evolution in the First Galaxies
Boyuan Liu, Yves Sibony, G. Meynet, Volker Bromm
Abstract
Abstract The James Webb Space Telescope (JWST) has revealed an unexpectedly high abundance of UV luminous galaxies at redshifts z ≳ 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 ∼3−6 when CHE stars above a minimum initial mass of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mi>m</mml:mi> <mml:mrow> <mml:mo>⋆</mml:mo> <mml:mo>,</mml:mo> <mml:mi>min</mml:mi> </mml:mrow> <mml:mi>CHE</mml:mi> </mml:msubsup> <mml:mo>∼</mml:mo> <mml:mn>2</mml:mn> <mml:mo>–</mml:mo> <mml:mn>10</mml:mn> <mml:mspace width="0.25em"/> <mml:msub> <mml:mi>M</mml:mi> <mml:mo>⊙</mml:mo> </mml:msub> </mml:math> 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 ∼ 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.