期刊
ASTROPHYSICAL JOURNAL
卷 805, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/805/2/180
关键词
ISM: structure; Galaxy: nucleus; radio continuum: ISM; scattering; techniques: interferometric
资金
- U.S. National Science Foundation [AST-1008865]
- Gordon and Betty Moore Foundation [GBMF-3561]
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1008865] Funding Source: National Science Foundation
At radio wavelengths, scattering in the interstellar medium distorts the appearance of astronomical sources. Averaged over a scattering ensemble, the result is a blurred image of the source. However, Narayan & Goodman and Goodman & Narayan showed that for an incomplete average, scattering introduces refractive substructure in the image of a point source that is both persistent and wideband. We show that this substructure is quenched but not smoothed by an extended source. As a result, when the scatter-broadening is comparable to or exceeds the unscattered source size, the scattering can introduce spurious compact features into images. In addition, we derive efficient strategies to numerically compute realistic scattered images, and we present characteristic examples from simulations. Our results show that refractive substructure is an important consideration for ongoing missions at the highest angular resolutions, and we discuss specific implications for RadioAstron and the Event Horizon Telescope.
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