VLA OBSERVATIONS OF 9 GALACTIC SUPERNOVA-REMNANTS

Using the VLA in different configurations we have observed the galacti c supernova remnants G7.7-3.7, G15.9+0.2, G18.8+0.3, G33.2-0.6, G46.8- 0.3, G340.4+0.4, G340.6+0.3, G341.9-0.3, and G342.0-0.2 in the radio c ontinuum at different frequencies. The current high quality observatio ns enabled us to detect small-scale structures and weak diffuse emissi on in the interior of several remnants. We have recalculated fluxes, d iameters and spectra, confirming previous estimates and improving them in some cases. At large scale the images were analized looking for tr aces of the influence of a non-uniform environment. In five out of the nine observed remnants, the brightest features occur on the side clos er to the galactic plane. At fine scale, morphological properties were inspected together with spectral inhomogeneities in order to investig ate whether the mechanisms that regulate the electron spectra can diff er from the processes responsible for brightness enhancements. Our stu dy shows that in general spectral variations coincide with brightness features, but the tendency of the relation is not uniform. Namely, G34 0.4+0.4 and G340.6+0.3 brighter regions have flatter spectra, while in G7.7-3.7, G15.9+0.2, and G341.9-0.3 the highest emissivity features a re the steepest, and in G18.8+0.3 no spectral variation was found, reg ardless of the brightness variations. Polarization observations were p erformed in G7.7-3.7, finding that polarization occurs preferentially on the half of the shell facing the galactic plane. (C) 1996 American Astronomical Society.