THE KINEMATICS AND EXCITATION OF MOLECULAR-HYDROGEN EMISSION IN THE PLANETARY-NEBULA BD -DEGREES-3639(30)

High spatial and spectral resolution spectra of the near-infrared H-2 emission from the planetary nebula BD +30 degrees 3639 are presented. A 7 '' x 13 '' portion of the nebula was mapped at a resolution of 600 0 in the upsilon = 1-0 S(1) emission line of molecular hydrogen, revea ling the morphology and kinematics of the H-2 emission, These spectra show large velocity shifts in the H-2 line across the nebula. Comparis on with single-dish CO observations show significant velocity differen ces between the peaks of H-2 emission and CO emission. Such difference s are unexpected for a photodissociation region (PDR), since PDRs are supposed to form in the surface of the cold gas las is the case for NG C 7027). A single long-slit spectrum which includes the peak of the H- 2 emission and covers the entire K band at a resolution of 1000 is ana lyzed. Fourteen molecular hydrogen emission lines are detected in a 2 '' x 0.'' 5 region covering the bright northeastern H-2 lobe. The line ratios indicate that the H-2 emission is radiatively excited, but tha t the gas density is large enough (n greater than or equal to 10(4.5)- 10(5) cm(-3)) for collisions to thermalize the lowest vibrational stat es. The measured ratio of ortho-hydrogen to para-hydrogen is 2.51 +/- 0.22, slightly smaller than the equilibrium value of 3. Spatial variat ions of the upsilon = 2-1 vibrational temperature and the upsilon = 1 ortho/para ratio are consistent with a decrease in the relative propor tion of collisional excitation as distance from the central star incre ases.