Journal article
A comparison of H-alpha intensity and radio wave scattering on eight low-latitude lines of sight
The Astrophysical journal, Vol.361(1), pp.116-120
09/1990
DOI: 10.1086/169173
Abstract
We have measured the Hα emission in the directions of eight extragalactic radio sources for which measurements of interstellar scattering have been made. We find that the diameter of the radio scattering disk at 1 GHz (θ_1 GHz_, a measure of the strength of scattering) is correlated with emission measure as determined from the Hα measurements. We also find that strong radio scattering characterized by θ_1 GHz_, 30 milliarcseconds is produced in regions with emission measures EM <~ 10^2^ cm^-6^ pc. The slope of the θ_1 GHz_-EM correlation is steeper than would be the case if all lines of sight were characterized by the same turbulent outer scale and "modulation index" (σ_n_/n_0_). A plausible interpretation of the observations is as follows: The lines of sight to unscattered or lightly scattered sources traverse only a diffuse medium, which is revealed by Hα observations at high latitudes. Heavily scattered sources are viewed through an additional component of interstellar H II, which has turbulence of different properties as regards rms density variation, outer scale, or both. Our results are consistent with a recent suggestion by Anatharamaiah and Narayan that strong radio wave scattering originates in extended, relatively low density envelopes of H II regions.
Details
- Title: Subtitle
- A comparison of H-alpha intensity and radio wave scattering on eight low-latitude lines of sight
- Creators
- Steven R SpanglerRonald J Reynolds
- Resource Type
- Journal article
- Publication Details
- The Astrophysical journal, Vol.361(1), pp.116-120
- DOI
- 10.1086/169173
- ISSN
- 0004-637X
- eISSN
- 1538-4357
- Publisher
- University of Chicago Press
- Language
- English
- Date published
- 09/1990
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199801602771
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