Subarcminute resolution images of Cas A at 74 and 333 MHz are presented. Comparison with each other and with higher frequency observations indicates that the spectral index of its nonthermal emission flattens below 333 MHz and that the effect is confined toward the central 1' of the source and is maximum at its center. The source of the flattening is unknown, although we show that the data are consistent with absorption by ionized gas inside the radio shell. Such a component may be related to unshocked ejecta still freely expanding within the boundaries of the reverse shock as delineated by X-ray observations. © 1995. The American Astronomical Society. All rights reserved. Printed in U.S.A.

Item Type:	Refereed Article
Research Division:	Physical Sciences
Research Group:	Astronomical and Space Sciences
Research Field:	Galactic Astronomy
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in the Physical Sciences
UTAS Author:	Erickson, WC (Professor William Erickson)
ID Code:	4828
Year Published:	1995
Web of Science® Times Cited:	31
Deposited By:	Physics
Deposited On:	1995-08-01
Last Modified:	2011-08-24
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