KINEMATICS OF THE IONIZED-GAS IN PUPPIS-VELA INCLUDING THE GUM NEBULA

We present a high resolution spectroscopic study of the ionised gas in Puppis-Vela, which includes the Gum Nebula and the IRAS Vela Shell, i n the emission lines of Halpha lambda6563 angstrom, [NII] lambdalambda 6548, 6584 angstrom and the [OIII] lambda5007 angstrom. Line profiles were obtained at 18 positions well distributed over the entire region. Only the [NII] line profiles in the region of the IRAS Vela Shell sho w double peaked profiles, consistent with an expansion velocity of 10 +/- 2km s-1. The ionised gas associated with the 36-degrees-diameter G um Nebula does not show any such systematic motions. This is consisten t with, and provides further confirmation of, the results obtained fro m the IRAS Super Sky Flux (ISSA) maps (Srinivasan Sahu & Blaauw 1993) that the IRAS Vela Shell and the Gum Nebula are two separate structure s but seen overlapping in projection. We detected no [OIII] lambda5007 angstrom emission in any of the positions observed. From the [NII]/Hal pha ratio, the temperatures derived at the 18 positions vary between 5 ,000 to 12,0000 K.