[Previous] | [Session 136] | [Next]
B.J. Hrivnak (Valparaiso U.), S. Kwok (U. Calgary), K.Y.L. Su, D.M. Kelly (Steward Obs, U. Arizona), R. Sahai (JPL/Caltech)
We carried out imaging and spectroscopic observations of the proto-planetary nebula IRAS 17150-3224. This object possesses a bipolar structure, with a dark lane separating the two lobes, and a series of concentric circumstellar arcs (Kwok et al. 1998, ApJ, 501, L117) reminiscent of th Egg Nebula. HST NICMOS images were obtained through narrow filters at H2 (F212N) and the adjacent continuum (F215N). These reveal H2 emission coming from clumps near the ends of the lobes; in addition there is some emission arising near the central star and faint emission from the lobes and from a loop at the ends of the obscuring lane. These again bear similarities to the Egg Nebula (Sahai et al. 1998, ApJ, 492, L163). Spectroscopic observations were made with Fspec on the Steward Obs. 2.3-m telescope. Strong H2 emission is seen from the 1-0 S(1) 2.122 \mum line, with weaker H2 emission from the 2-1 S(1) 2.248 \mum, 1-0 S(0) 2.223 \mum, 3-2 S(3) 2.201 \mum, and 2-1 S(2) 2.154 \mum lines. From the line ratios, we conclude that the emission is collisionally excited. This we attribute to a shock formed by the impact of the fast outflow from the star with the denser remnant circumstellar envelope of the AGB progenitor. This work was funded in part by grants to BJH from NASA and the NSF, to SK from NERSC, and to RS from NASA.