October 2025
Abstract
The discovery of high ionization emission lines in both high-redshift galaxies and nearby, metal-poor dwarf galaxies has questioned the origin of He II ionizing radiation. Current stellar population synthesis models consistently fail to reproduce the necessary ionizing fluxes, pointing to a fundamental gap in our understanding of stellar feedback and its role in cosmic reionization. Classical Wolf-Rayet (WR) stars are hot, evolved massive stars with depleted hydrogen. WR stars with prominent Nitrogen emission lines in their spectra are called WN type, further sub-divided as 'early' (WNE) when showing emission from high ionization species (e.g., He II, N V). WNE stars at low metallicity are huge contributors to the HeII ionizing flux of their host galaxy. However, the presence of WNE stars in integrated environments can be diluted, making their direct spectroscopic detection challenging. In this talk, I will directly compare stellar spectral diagnostics for the resolved WNE stars in our nearest low-metallicity dwarf galaxy, the SMC, with integrated nebular diagnostics from the Local Volume Mapper integral field survey. I will discuss the implications of our unexpected findings for population synthesis models and galaxy evolution.