New Models for Wolf-Rayet and O Star Populations in Young Starbursts

摘要: Using the latest stellar evolution models, theoretical spectra, and a compilation of observed emission line strengths from Wolf-Rayet (W-R) stars, we construct evolutionary synthesis models for young starbursts. We explicitly distinguish between various W-R subtypes (WN, WC, WO), whose relative frequency is strong function metallicity, treat O Of stars separately. calculate numbers produced during starburst provide detailed predictions UV optical both lines major nebular hydrogen helium lines, as several input parameters related to episode. also derive W-R-rich Our predict that He II λ4686 low-metallicity should be associated with presence WC/WO and/or hot WN evolving become stars. In addition, contribute broad components beneath Balmer lines; component may constitute percent total flux in line. review techniques used star content integrated assess their accuracy, propose two new formulae estimate W-R/O number ratio or spectra. explore implications formation through mass transfer close binary systems instantaneous bursts. While Roche lobe overflow prolongs W-R-dominated phase, there are clear observational signatures allow us phases which formed predominantly single channels. particular at low metallicities, when massive binaries significantly binary-dominated phase expected occur ages corresponding relatively Hβ equivalent widths. The features predicted by our quantitative determination population region (particularly so-called "W-R galaxies") its spectrum means deriving burst properties (e.g., duration age) initial model most reliable determinations date. They can test current theories atmospheres investigate variation metallicity.