On the Origins of the High-Latitude H-alpha Background
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.
Keywords
Cite
@article{arxiv.1010.4361,
title = {On the Origins of the High-Latitude H-alpha Background},
author = {A. N. Witt and B. Gold and F. S. Barnes and C. T. DeRoo and U. P. Vijh and G. J. Madsen},
journal= {arXiv preprint arXiv:1010.4361},
year = {2015}
}
Comments
26 pages, 5 figures, Accepted for publication in ApJ