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Galactic Free-free and H-alpha Emission

George F. Smoot
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Abstract

This document provides a brief summary estimate of Galactic free-free emission and H-alpha emission and their relationship. Particular emphasis is placed on estimating the potential free-free emission in the region of significant confusion for CMB anisotropy measurements. Existing x-ray, ultraviolet and H$α$ emission provide limits on the radio free-free emission and vice versa. These limits are generally somewhat smaller than the observed ``free-free'' (signal proportional to frequency^{-2.15}) microwave signal. If this remains true, then some previously neglected source may be present. Physics argues that H-alpha emission is still the best tracer for Galactic free-free emission and thus a tool for diagnosing if there is a previously neglected emssion source.

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George F. Smoot. 1998-01-14. Galactic Free-free and H-alpha Emission. https://arxiv.org/abs/astro-ph/9801121

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