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Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2007

The effects of spatially distributed ionization sources on the temperature structure of HII regions

Résumé

Spatially resolved studies of star-forming regions show that the assumption of spherical geometry is not realistic in most cases, with a major complication posed by the gas being ionized by multiple non-centrally located stars or star clusters. Geometrical effects including the spatial configuration of ionizing sources affect the temperature and ionization structure of these regions. We try to isolate the effects of multiple non-centrally located stars via the construction of 3D photoionization models using the 3D Monte Carlo photoionization code MOCASSIN with very simple gas density distributions, but various spatial configurations for the ionization sources. Our first aim is to study the resulting temperature structure of the gas and investigate the behaviour of temperature fluctuations within the ionized region. We show that geometry affects the temperature structures in our models differently according to metallicity. For the geometries and stellar populations considered in our study, at intermediate and high metallicities, models with ionizing sources distributed in the full volume, whose Strömgren spheres rarely overlap, show smaller temperature fluctuation than their central ionization counterparts, with fully overlapping concentric Strömgren spheres. The reverse is true at low metallicities. Finally, the true temperature fluctuations due to the stellar distribution (as opposed to the large-scale temperature gradients due to other gas properties) are small in all cases and not a significant cause of error in metallicity studies.
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Dates et versions

hal-03732878 , version 1 (08-09-2022)

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Barbara Ercolano, Nate Bastian, Grazyna Stasinska. The effects of spatially distributed ionization sources on the temperature structure of HII regions. Monthly Notices of the Royal Astronomical Society, 2007, 379, pp.945-955. ⟨10.1111/j.1365-2966.2007.12002.x⟩. ⟨hal-03732878⟩
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