Global photometric analysis of Galactic HII regions

Abstract

Total infrared fluxes are estimated for 99 HII regions around massive stars. The following wavebands have been used for the analysis: 8 and 24 μm, based on data from the Spitzer Space Telescope (IRAC and MIPS, respectively); 70, 160, 250, 350 and 500 μm, based on data from the Herschel Space Observatory (PACS and SPIRE). The estimated fluxes are used to evaluate the polycyclic aromatic hydrocarbon (PAH) mass fraction (q PAH) and the intensity of ultraviolet emission in the studied objects. It is shown that the PAH mass fraction, q PAH, is much lower in these objects than the average Galactic value, implying effective destruction of aromatic particles in HII regions. Estimated radiation field intensities (U) are close to those derived for extragalactic HII complexes. Color indices [F 24/F 8], [F 70/F 24], [F 160/F 24] and [F 160/F 70] are compared to criteria proposed to distinguish between regions of ionized hydrogen and planetary nebulae. Also, we relate our results to analogous color indices for extragalactic complexes of ionized hydrogen. © 2018 National Astronomical Observatories, CAS and IOP Publishing Ltd..