1. Injection of Small Bodies into the ISM by Planetary Nebulae. Bob O’Dell University of Chicago 18 April 2007

2. NGC 6720- The Ring Nebula

3. IC 4406- The Retina Nebula

4. NGC 2392 The Eskimo Nebula

5. NGC 6853 WFPC2

6. Final.Dec16XV.tif

7. Helix-Both FOV

8. Helix Close-up

9. Helix-Very Closeup

10. Helix Characteristics Distance=213 pc. Angular Size~10’ Age ~15,000 years Well imaged in optical lines (HST-ACS & CTIO-MOSAIC), infrared (HST-NIC3-H 2 ), and Radio (21-cm of HI, CO)

11. Ionization Structure

12. GO 9489 Slit

13. Slitless.fourlines

14. NewProfiles

15. HenneyConstTemp

16. HenneyVariableT

17. Predicting the Surface Brightness of the Knot Cusps. The most simplistic model argues that the surface brightness should drop with r -2, which meant this should be the upper limit to an observed S H  ~  -2 relation.

18. Observed Surface Brightness

19. Predicting the Surface Brightness of the Knot Cusps. The most simplistic model argues that the surface brightness should drop with r -2, which meant this should be the upper limit to an observed S H  ~  -2 relation. Due to advection of neutral material into the ionized cusp, not all photons reach the ionization front of the cusps (Lopez-Martin et al. 2001, ApJ, 548, 288) so that the upper limit should be lower.

20. Predicted Surface Brightness

21. Knot Characteristics Total Number about 3,500-20,000. Mass from extinction~3x10 -5 Suns. Total mass about 0.1-0.6 Suns. The central star mass is about 0.6 Suns. The original mass is about 3 Suns. A significant and possibly majority fraction of the mass is concentrated in knots.

22. Evolution of Knots Initiated at the ionization front via an instability (R-T, Capriotti 1973). Shaped by the radiation field of the star, starting out as broad and becoming comet-like in appearance.

23. Final Evolution of a Central Star.

24. Shadows behind the Knots. The first order theory has been worked out already (Canto et al. 1998, ApJ, 502, 695. Since the knots are optically thick to LyC, they cast an ionization shadow. Some ionization occurs because of LyC photons scattered by the ambient nebula.

25. The Bulk of the Mass is in the Neutral Region of the Knots. Densities inferred from the optical are about 10 6 cm -3. Only one study of a heavy molecule (CO). H 2 is expected to be the dominant form of hydrogen in the outer parts of the knots.

26. The Bulk of the Gas is in the Neutral Region and H 2 is the strongest emission from there.

27. The H2 Levels

28. The NIC3 FOV in GO 10628

29. Northern FOV in Multiple Lines.

30. Profiles of 378-801 in the Emission Lines.

31. Mechanisms Proposed to Power the H 2 Emission. Shocks driven by a high velocity wind from the central star.

32. Mechanisms Proposed to Power the H 2 Emission. Shocks driven by a high velocity wind from the central star. Pumping by the FUV continuum followed by decay (the Solomon process).

33. The H2 Levels

34. Mechanisms Proposed to Power the H 2 Emission. Shocks driven by a high velocity wind from the central star. Pumping by the FUV continuum followed by decay (the Solomon process). Photodissociation by x-rays followed by collisional heating of the gas.

35. Mechanisms Proposed to Power the H 2 Emission. Shocks driven by a high velocity wind from the central star. Pumping by the FUV continuum followed by decay (the Solomon process). Photodissociation by x-rays followed by collisional heating of the gas. Photodissociation by EUV (the LyC) followed by collisional heating.

36. The Energy Balance. IN: X-ray(<124 A) 4x10 -11 ergs cm -2 s -1 IN: FUV (912-1200 A) 7x10 -9 ergs cm -2 s -1 IN: EUV (124-912 A) 8x10 -8 ergs cm -2 s -1 Out: Ionized Gas Lines 5x10 -9 ergs cm -2 s -1 Out:H 2 Emission Lines 4x10 -9 ergs cm -2 s -1

37. The Population Distribution.

38. The EUV Driven Model. This must have a density >10 5 cm -3. It must have a collisionally heated gas of about 990 K. It must have a zone where H 2 still exists and yet there are LyC photons. The key physics is in advection, which was necessary for explaining the surface brightness in Ha and the electron temperature increase in the ionized gas zone.

39. Evolution of Knots-I Will they survive the expulsion phase? Almost certainly they will survive the high LyC luminosity phase of the central star since the photoevaporation time is about 15,000 years and it must decrease as the star gets fainter.

40. Evolution of Knots-II The question then is whether they will survive destruction by the diffuse UV radiation field of the ISM before being incorporated into GMC’s. There is ample and growing evidence for small scale structures in the ISM. This process could be the source.

41. Helix Reading 3-D Model-O’Dell et al. 2004,AJ,128,2339& RMxAAC, 23, 5. 3-D Model-Meaburn et al. 1998,MNRAS,294,201& 2005,MNRAS,360,963. Knot Ubiquity-O’Dell et al. 2002,AJ,123,3329. Knot Basics-O’Dell & Burkert, 1997,IAU180, 332. Detailed Knot Modeling-O’Dell, Henney, & Ferland 2005,AJ,130,172. H 2 Observations-Meixner et al. 2005,AJ,130,1784. H 2 Energetics-O’Dell, Henney, & Ferland 2007, AJ, 133, 2343.