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Session 10 - Spiral Galaxies.
Display session, Monday, June 10
Great Hall,
NGC 3432 appears to provide a counter-example to the notion that high latitude H\alpha emission, either in the form of an extended diffuse layer (DIG) or in discrete features, correlates with the existance of a strong non-thermal radio contiuum halo. VLA data displays a radio halo extending up to 5.3 kpc above the plane as well as radio ``spurs''. These latter features do not appear, in general, to align with regions of star formation in the disk nor with discrete ionized features. If this near edge-on galaxy had a DIG component similar to that of NGC 891, it would likely be detected in our narrowband H\alpha CCD images acquired at Mont Megantic (sensitivity = 1.2 \times 10^-16\ erg \ cm^2 \ s^-1\ arcsec^-2). Our non-detection of an ionized halo is consistent with the suggestion that only galaxies with FIR luminosities greater than 3 \times \ 10^43 \ erg\ s^-1 have both a thick radio continuum disk and a thick ionized layer. Since there is no strong correlation between star formation regions and the morphology of the radio halo, this extended radio continuum may be a product of the interaction between NGC 3432 and UGC 5983 rather than the result of a connection between the disk and halo of NGC 3432.
