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A Review of Radio Interferometric Imaging of Comets

Published online by Cambridge University Press:  12 April 2016

Imke de Pater ,
Patrick Palmer  and
Lewis E. Snyder
Imke de Pater
Affiliation:
Astronomy Department 601 Campbell, Hall University of California, Berkeley, CA 94720
Patrick Palmer
Affiliation:
Department of Astronomy and, Astrophysics University of Chicago 5640 South Ellis Ave. Chicago, IL 60637
Lewis E. Snyder
Affiliation:
Department of Astronomy, University of Illinois 349 Astronomy Bldg. 1011 W. Springfield Ave. Urbana, IL 61801

Abstract

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We present an overview of cometary observations carried out with the VLA. These include OH imaging observations, studies of other molecules and searches for continuum emission. Primarily, we discuss the OH observations obtained of Comet Halley, a periodic comet, and Comet Wilson, a “new” comet. The emission from Comet Halley is confined to a region a few times 105 km. The emission from Comet Wilson shows sporadic blobs at large distances (∼ 106 km from the center), which vary abruptly in both position and velocity. The generally accepted picture of excitation by UV pumping in a spherical outflow of cometary gas explains the coarse phenomenology, but other effects seem to cause significant modulations of the OH emission. We suggest that for Comet Halley, collisional effects near the edge of the quenching region, which is coincidently the approximate distance to the cometopause, may be important, and that for Comet Wilson, outgassing from cometesimals ejected from the nucleus may be significant. We further show that asymmetric line profiles are more common than previously thought. Lengthening integration times and lowering the velocity resolution results in a smooth, round shape for the comet’s brightness distribution. In addition, spectral profiles become broader and more symmetric after long integration times and after integration over larger spatial regions. In addition to the OH observations we summarize the H2CO detection experiments for comets Halley and Machholz.

Type
Section I: Observing Techniques and Interpretation
Information
International Astronomical Union Colloquium , Volume 116 , Issue 1: Comets in the Post-Halley Era , 1989 , pp. 175 - 207
Copyright
Copyright © Kluwer 1991

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