Extinction Variations in the H II Regions Sharpless 156 and 162

156-162 RAZVODOSKY.indd

Dust extinction of H ii regions in NGC 598 and NGC 5457 ⋆

The dust extinction towards bright H ii region-sin NGC 598 and NGC 5457 has been studied in detail by forming line ratios of Balmer and Paschen emission lines covering a large wavelength range. Three homogeneous models of the geometrical distribution of the emitting sources and the obscuring dust have been tested. Only for low extinctions can the data be fit by a homogeneous slab. For most of t...

Ultracompact H Ii Regions

RESUMEN Discutimos algunos resultados observacionales recientes sobre regiones H II ultracompactas. En particular, discutimos la emisión extendida de algunas regiones H II UC y el descubrimiento de una nueva clase, denominada regiones H II " hipercompactas ". Además, describimos la obtención de la estructura de densidad usando la técnica del análisis deí ındice espectral. ABSTRACT We discuss so...

Lyman Continuum Extinction by Dust in H Ii Regions of Galaxies

We examine Lyman continuum extinction (LCE) in H II regions by comparing infrared fluxes of 49 H II regions in the Galaxy, M31, M33, and the LMC with estimated production rates of Lyman continuum photons. A typical fraction of Lyman continuum photons that contribute to hydrogen ionization in the H II regions of three spiral galaxies is . 50 %. The fraction may become smaller as the metallicity ...

There’s Life in H Ii Regions Yet!

We give an overview of the literature on ionization front structure and propagation and comment on recombination front structures. We discuss the formation of cometary tails by photoionization of globules and note the importance of including the diffuse component of the ionizing radiation field. We finally briefly comment on the formation of small scale structures in H II regions.