Photoionization models of NGC 346

Abstract

We have compared direct estimates of the ionizing photon flux from the stars observed within the H II region NGC 346 in the Small Magellanic Cloud with its observed Hα luminosity using a series of photoionization models of the region. The tests were based on the use of the photoionization code Cloudy (Ferland 2000), aided by H, He, N, O, Ne, S, Ar, and Fe emission line observations of Peimbert, Peimbert, & Ruiz (2000, hereinafter PPR). A key result is that some 46% of the Lyman continuum photons escape from the region. The abundances of N, O, Ne, S, Ar, and Fe relative to H were determined using the ionization structure of the best model, and are compared with those derived from empirical ionization correction factors.