Eruptive Mass Loss in Massive Stars: From Stellar Evolution to Galaxies

Abstract

Among the uncertain ingredients in massive star evolution, mass loss is especially central. It determines how much hydrogen envelope survives to core collapse, whether a star ends its life as a red, yellow, or blue supergiant, and what compact remnant it leaves behind. Yet the physical mechanisms driving mass loss, particularly its eruptive component, remain poorly constrained, and standard prescriptions are increasingly in tension with observations. This thesis develops a physically motivated model for eruptive, super-Eddington mass loss and traces its consequences across several scales. We begin by asking whether stellar mass loss in star-forming quasar accretion disks can explain why quasar broad-line region metallicities appear to saturate near 9 solar metallicity. We then develop and implement in MESA a one-dimensional model in which envelope material is ejected wherever local super-Eddington radiative luminosity exceeds the gravitational binding energy of the overlying layers. We calibrate this prescription against red supergiant luminosity functions in the SMC, LMC, and M31, finding that the preferred eruptive efficiency increases systematically with metallicity. Finally, we show that these calibrated models leave measurable imprints on the integrated light of unresolved stellar populations, with the strongest signatures in the near-infrared. Together, the results connect envelope physics to chemical enrichment, the demographics of evolved massive stars, and the light of galaxies and quasars.