\title{HII Structures in the Middle Disk of M31}

\author{W. Ashman, J. S. Gallagher, E. Wilcots} \affil{University of Wisconsin---Madison} \begin{abstract} We present a deep, narrow-band H$\alpha +$ [N II] image that shows a variety of emission line objects in the middle disk of M31 along the minor axis. The observations were obtained with the WIYN 3.5-m telescope under excellent conditions with 0.7 arcsec FWHM images. These data include the large HII regions 405 and 406, catalogued by Baade \& Arp (1964, ApJ, 139, 1027) in the main star-forming ring of M31, as well as smaller HII regions in the inner disk. In addition several faint, large ionized shells and numerous unresolved sources are present. We analyze the symmetries of larger ionized structures as a means to search for the effects of an anisotropic pressure component that could be produced by an organized, large-scale magnetic field. The taxonomy of ionized structures in this part of M31 also is briefly summarized. \end{abstract} Date: Fri, 5 Apr 96 18:32:53 EST 

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