Axial Ratio of Edge-On Spiral Galaxies as a Test For Extended Bright
  Radio Halos
  We use surface brightness contour maps of nearby edge-on spiral galaxies to
determine whether extended bright radio halos are common. In particular, we
test a recent model of the spatial structure of the diffuse radio continuum by
Subrahmanyan and Cowsik which posits that a substantial fraction of the
observed high-latitude surface brightness originates from an extended Galactic
halo of uniform emissivity. Measurements of the axial ratio of emission
contours within a sample of normal spiral galaxies at 1500 MHz and below show
no evidence for such a bright, extended radio halo. Either the Galaxy is
atypical compared to nearby quiescent spirals or the bulk of the observed
high-latitude emission does not originate from this type of extended halo.
