Infrared Planetary Nebulae in the NRAO VLA Sky Survey

Abstract

The 1.4 GHz NRAO VLA Sky Survey (NVSS) images and source catalog were used to detect radio emission from the 885 planetary nebulae north of J2000 declination {J = - 40° in the Strasbourg-ESO Catalogue of Galactic Planetary Nebulae. We identified 680 radio sources brighter than about S = 2.5 mJy beam - 1 (equivalent to T :::: 0.8 K in the 45" FWHM NVSS beam) with planetary nebulae by coincidence with accurate optical wsitions measured from Digitized Sky Survey (DSS) images. Total extinction coefficients c at A. = 4861 A were calculated for the 429 planetary nebulae with available H/3 fluxes and low free-free optical depths at 1.4 GHz. The variation of c with Galactic latitude and longitude is consistent with the extinction being primarily interstellar and not intrinsic.