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ON THE ORIGINS OF THE HIGH-LATITUDE H{alpha} BACKGROUND
Ist Teil von
The Astrophysical journal, 2010-12, Vol.724 (2)
Ort / Verlag
United States
Erscheinungsjahr
2010
Link zum Volltext
Quelle
EZB Free E-Journals
Beschreibungen/Notizen
The diffuse high-latitude H{alpha} background is widely believed to be predominantly the result of in situ recombination of ionized hydrogen in the warm interstellar medium of the Galaxy. Instead, we show that both a substantial fraction of the diffuse high-latitude H{alpha} intensity in regions dominated by Galactic cirrus dust and much of the variance in the high-latitude H{alpha} background are the result of scattering by interstellar dust of H{alpha} photons originating elsewhere in the Galaxy. We provide an empirical relation, which relates the expected scattered H{alpha} intensity to the IRAS 100 {mu}m diffuse background intensity, applicable to about 81% of the entire sky. The assumption commonly made in reductions of cosmic microwave background observations, namely that the observed all-sky map of diffuse H{alpha} light is a suitable template for Galactic free-free foreground emission, is found to be in need of reexamination.