| Abstract: | We present new spectral (FPI and long‐slit) data on the Eastern optical filament of the well known radionebula W50 associated with SS433. We find that on sub‐parsec scales different emission lines are emitted by different regions with evidently different physical conditions. Kinematical properties of the ionized gas show evidence for moderately high (V ～ 100 km s–1) supersonic motions. O III]λ 5007 emission is found to be multi‐component and differs from lowerexcitation S II]λ 6717 line both in spatial and kinematical properties. Indirect evidence for very low characteristic densities of the gas (n ～ 0.1 cm–3) is found. We propose radiative (possibly incomplete) shock waves in low‐density, moderately high metallicity gas as the most probable candidate for the power source of the optical filament. Apparent nitrogen overabundance is better understood if the location of W50 in the Galaxy is taken into account (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) |
