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We present the warpfield emission predictor, warpfield-emp , which couples the 1D stellar feedback code warpfield with the cloudy H  ii region/PDR code and the polaris radiative transfer code, in order to make detailed predictions for the time-dependent line and continuum emission arising from the H  ii region and PDR surrounding an evolving star cluster. warpfield-emp accounts for a wide range of physical processes (photoionization, stellar winds, supernovae, radiation pressure, gravity, thermal conduction, radiative cooling, dust extinction etc.) and yet runs quickly enough to allow us to explore broad ranges of different model parameters. We compare the results of an extensive set of models with SITELLE observations of a large sample of H  ii regions in NGC 628 and find very good agreement, particularly for the highest signal-to-noise observations. We show that our approach of modelling individual clouds from first principles (instead of in terms of dimensionless quantities such as the ionization parameter) allows us to avoid long-standing degeneracies in the interpretation of H  ii region diagnostics and enables us to relate these diagnostics to important physical parameters such as cloud mass or cluster age. Finally, we explore the implications of our models regarding the reliability of simple metallicity diagnostics, the properties of long-lived embedded clusters, and the role played by winds and supernovae in regulating H  ii region and PDR line emission. [ABSTRACT FROM AUTHOR]

The shape of OB-star ionizing spectral energy distributions (SEDs) is a critical component in many diagnostics of galaxy and interstellar medium properties. To quantitatively examine the shape of the OB-star SED, we compare long slit observations of single-star, Large Magellanic Cloud H II regions to the predictions from CLOUDY photoionization simulations that use CoStar, TLUSTY, and WM-basic stellar atmosphere models as the ionizing source. For each atmosphere model, we run grids of Hii region simulations with the effective temperature (Teff ) of the star as a free parameter. The best SEDs from each atmosphere code are found by matching the predicted emission-line spectra with those observed from the nebulae. By assuming a clumpy gas distribution, all atmosphere codes are able to reproduce the observed emission lines, except at the highest energy transitions ≳40 eV. Taking into account both low and high energy transitions, we find that simulations usingWM-basic produce the best agreement with the observed line ratios. The rates of ionizing photons from different atmosphere models vary systematically with the relative hardness of the SEDs. However, in general the rates produced by the model SEDs, for standard log(g) = 4.0 models, are consistent with the rates derived from the Hα luminosities. We find that our effective temperatures inferred from the nebular ionization balance are consistent with those predicted by conventional photospheric-based calibrations from the literature. We suggest that future spectral type to Teff calibrations can be constructed from nebular data. [ABSTRACT FROM AUTHOR]

We use our new optical-imaging and spectrophotometric survey of key diagnostic emission lines in 30 Doradus, together with CLOUDY photoionization models, to study the physical conditions and ionization mechanisms along over 4000 individual lines of sight at points spread across the face of the extended nebula, out to a projected radius 75 pc from RI36 at the center of the ionizing cluster NGC 2070. We focus on the physical conditions, geometry, and importance of radiation pressure on a point-by-point basis, with the aim of setting observational constraints on important feedback processes. We find that the dynamics and large-scale structure of 30 Dor are set by a confined system of X-ray bubbles in rough pressure equilibrium with each other and with the confining molecular gas. Although the warm (10,000 K) gas is photoionized by the massive young stars in NGC 2070, the radiation pressure does not currently play a major role in shaping the overall structure. The completeness of our survey also allows us to create a composite spectrum of 30 Doradus, simulating the observable spectrum of a spatially unresolved, distant giant extragalactic H n region. We find that the highly simplified models used in the "strong line" abundance technique do in fact reproduce our observed line strengths and deduced chemical abundances, in spite of the more than one order of magnitude range in the ionization parameter and density of the actual gas in 30 Dor. [ABSTRACT FROM AUTHOR]

We develop the technique of ionization parameter mapping (IPM) to probe the optical depth of Hii regions, applying our method to the Magellanic Clouds. Our results dramatically clarify the radiative transfer in these galaxies. Based on Sii, Oiii, and Hα imaging from the Magellanic Clouds Emission Line Survey, we find that the frequency of optically thin objects correlates strongly with Hα luminosity and correlates inversely with Hi column density. The aggregate escape fraction for the Lyman continuum is sufficient to ionize the diffuse, warm ionized medium, but the galactic escape fraction is dominated by the few largest Hii regions. The quantitative trends are similar in both the LMC and SMC in spite of their different star formation and Hi properties. [ABSTRACT FROM AUTHOR]