Single-Star HII Regions as a Probe of Massive Star SEDs
Department of Astronomy, 500 Church Street, University of Michigan, Ann Arbor, MI, 48109, USA
Department of Astronomy, 500 Church Street, University of Michigan, Ann Arbor, MI, 48109, USA
Department of Astronomy, 500 Church Street, University of Michigan, Ann Arbor, MI, 48109, USA
Abstract
We critically examine stellar atmosphere models by exploiting the strong dependence of HII region optical spectra on the SED of the ionizing source. To accomplish this, we compare spatially resolved, longslit observations of LMC single-star HII regions to photoionization simulations based on observed nebular and stellar properties. We select stellar atmosphere models from the CoStar (Schaerer & de Koter, 1997), TLUSTY (Lanz & Hubeny, 2003), WM-basic (Pauldrach et al. 2001) and Smith et. al. (2002) grids to define the ionizing source in our simulations. Gas density fluctuations are necessary to simultaneously fit the emission from high and low excitation ions. We evaluate the atmospheres relative to each other and overall, find atmosphere models using the WM-basic code have the best agreement with our observations.