Spectral energy distribution of compact planetary nebulae.

The spectral energy distributions between 0.1 and 100 microns of 66 compact planetary nebulae are presented. The observed energy distributions are fitted with a model consisting of the stellar, nebular, and dust components. It is found that on the average, 38 +/-21, 25 +/-16, and 37 +/-14 percent of the emergent fluxes in the above wavelength range are emitted by the stellar, nebular, and dust components, respectively. When the derived stellar temperature is used to deduce the total emitted flux from the central star and the result is compared with the total observed flux, it is found that most (about 90 percent) of the nebulae are ionization-bounded. The empirical ratio between the total observed flux and the H-beta flux has a median of 160, which is consistent with the empirical stellar to H-beta luminosity ratio of 150 derived by Gathier and Pottasch (1989) for a sample of extended nebulae.