On the hardening of the ionizing radiation in HII regions across galactic discs through softness parameters - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate




On the hardening of the ionizing radiation in HII regions across galactic discs through softness parameters - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We carry out a study of the hardness of the radiation of ionizing clusters inHII regions. Firstly, we explore the applicability of the softness parameter,originally defined in the optical for pairs of consecutive ionization stages ofthe same species. With the advent of the infrared space observatories, thisdefinition has been extended to the mid-infrared. We show that the softnessparameters, as determined both in the optical and the mid-infrared wavelengths,are sensitive to the effective temperature using a sample of data in bothspectral regimes. This is confirmed by comparing the data with a grid ofphotoionization models, although no complete agreement has been found even fordifferent stellar model atmospheres. Finally, we show that both softnessparameters are consistent in the search for radial variations of the hardnessof the ionizing radiation of HII regions in the discs of spiral galaxies. Wefind a range of trends, from galaxies showing pronounced gradients to thoseshowing very flat ones. Although the detectability and slope of these gradientscan be altered by the size and luminosity of the studied HII regions, it looksthat their existence is related to the mass and type of the galaxies and,hence, to the roperties of the entire disc.



Author: Enrique Perez-Montero IAA-CSIC, Jose M. Vilchez IAA-CSIC

Source: https://arxiv.org/







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