NCSA Astronomy Digital Image Library
Project Abstract and Description
Relativistic electron populations in Cassiopeia A
M. Anderson, L. Rudnick, P. Leppik, R. Perley, and R. Braun
Contact: R. Perley
Email: rperley@nrao.edu
Number of images in project: 1
References: 1991ApJ...373..146A
Abstract
The radio structure of the galactic supernova remnant Cas A is complex
and is distributed over a variety of spatial scales. A few major
components are apparent. The most prominent is a bright ring of radio
emission at a radius of approximately 110" (1.7 pc at a distance of 2.9 pc).
This bright ring is generally associated with a region of high magnetic
field, amplified through Rayleigh-Taylor instabilities which develop at
the contact surface between the comparatively dense supernova ejecta
and the shock-heated interstellar medium as the remnant begins to
decelerate. The bright ring has an expansion age of 950 yr, much
longer than that of the fast-moving optical knots situated at a similar
radius (300 yr), indicating that a substantial deceleration of the
radio-emitting ejecta has already occurred. A plateau, or outer shell,
of material is seen out to a radius of 140". A set of eleven
paraboloidal features or bow shocks may indicate clumps of fast-moving
ejecta which have penetrated the decelerated shell and are generating
bow shocks in the material beyond the shells. The remnant is also
covered by a network of faint filamentation, the nature of which is
still unclear. These may be actual filaments of compressed gas,
condensed under some type of cooling or dynamical instability, or
perhaps they are features of numerous intersecting shock waves
propagating through the remnant.
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