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arXiv · 1010.4361

On the Origins of the High-Latitude H-alpha Background

A. N. Witt·B. Gold·F. S. Barnes III·C. T. DeRoo·U. P. Vijh·G. J. Madsen
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Abstract

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 100um diffuse background intensity, applicable to about 81% of the entire sky. The assumption commonly made in reductions of CMB 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.

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A. N. Witt, B. Gold, F. S. Barnes III, C. T. DeRoo, U. P. Vijh, G. J. Madsen. 2010-10-21. On the Origins of the High-Latitude H-alpha Background. https://doi.org/10.1088/0004-637x%2F724%2F2%2F1551

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