1. W.J. Maciel, R.D.D. Costa, T.E.P. Idiart IAG/USP – São Paulo - Brazil
Extra-galactic Planetary Nebulae Workshop
Garching, May 2004
CHEMICAL COMPOSITION OF PLANETARY NEBULAE: MAGELLANIC CLOUDS AND THE GALAXY
W.J. Maciel, R.D.D. Costa, T.E.P. Idiart IAG/USP – São Paulo - Brazil

2. ABSTRACT
We compare the chemical composition of planetary nebulae in three different systems: the Galaxy, the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC).
The data has been gathered by the IAG/USP group during the last decade in a homogeneous procedure, emphasizing distance-independent correlations.
We show that most abundance correlations hold
for all three systems, taking into account the observed metallicity differences between the Galaxy and the Magellanic Clouds.

3. PLAN OF THE TALK 1. Introduction 2. The data
3. Distance-independent correlations
3.1 Planetary nebulae and HII regions
3.2 Correlations with S, Ar, Ne and O
3.3 Correlations with N
3.4 Correlations with He
4. Anticenter PN: the radial gradient
5. PN in the galactic bulge

4. 1. Introduction
Several hundred planetary nebulae have been detected in the Magellanic Clouds. However, accurate abundances are available only for a fraction of these objects. In this work, we will discuss some recent results on the chemical composition of planetary nebulae in three different systems: the Milky Way (MW), the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). We will emphasize our own results and distance–independent correlations, but will also try to relate the low metallicity systems LMC/SMC with the metal poorer regions of the galactic anticenter.

5. 2. The data
In the last decade, the chemical compositions of almost three hundred planetary nebulae have been determined by the IAG/USP group, using both the 1.52 m ESO telescope at La Silla and the 1.6 m LNA telescope at Brasopolis, Brazil.
The main characteristics of this work are the high degree of homogeneity of the observational and reduction procedures, and in the analysis of the chemical abundances.

6. PN in the dataset of the IAG/USP group

7. 3. Distance-independent correlations
3.1 Planetary nebulae and HII regions
The abundances of elements such as He, S, Ne, Ar, and O are similar both in the PN and HII regions of each system. The main differences appear for Nitrogen, which is dredged up in the PN progenitor stars.

8. Average abundances of PN and HII regions

9. Abundance differences: PN minus HII regions
figure 1
Abundance differences: PN minus HII regions

10. 3. Distance-independent correlations
3.2 Correlations with S, Ar, Ne and O
The elements S, Ar and Ne are not expected to be produced by the PN progenitor stars. Oxygen may have been somewhat altered by ON cycling, as we will investigate later.
Whenever applicable, we will compare our data with the results of the extensive survey by Stasinska et al. (1998, Astron. Astrophys. 336, 667) .

11. Sulphur: the S/H x O/H correlation
figure 2
Sulphur: the S/H x O/H correlation

12. Argon: the Ar/H x O/H correlation
figure 3
Argon: the Ar/H x O/H correlation

13. Neon: the Ne/H x O/H correlation
figure 4
Neon: the Ne/H x O/H correlation

14. 3. Distance-independent correlations
3.3 Correlations with N
As we have seen, nitrogen is dredged up in the progenitor stars, so that its abundance has been altered with relation to the interstellar values.
Some N/O x O/H anticorrelation is observed, as reported by some authors, especially for the LMC and SMC nebulae. This is also reflected in the N/H x O/H correlation.
Nitrogen can also be used in the comparison of the observed N/O x N/H correlation with the relation predicted by theoretical models for the LMC (Groenewegen and de Jong, A&A 282, 127, 1994).

15. Nitrogen: the N/O x O/H anticorrelation
figure 5a
Nitrogen: the N/O x O/H anticorrelation

16. Nitrogen: the N/O x O/H anticorrelation
figure 5b
Nitrogen: the N/O x O/H anticorrelation

17. Nitrogen: the N/O x O/H anticorrelation
figure 5c
Nitrogen: the N/O x O/H anticorrelation

18. Nitrogen: the N/O x O/H anticorrelation
figure 5d
Nitrogen: the N/O x O/H anticorrelation

19. Nitrogen: the N/O x O/H anticorrelation
figure 5e
Nitrogen: the N/O x O/H anticorrelation

20. Nitrogen: the N/H x O/H correlation
figure 6a
Nitrogen: the N/H x O/H correlation

21. Nitrogen: the N/H x O/H correlation
figure 6b
Nitrogen: the N/H x O/H correlation

22. Nitrogen: the N/O x N/H correlation and model
Groenewegen and de Jong (1994)
figure 7a
Nitrogen: the N/O x N/H correlation and model

23. Nitrogen: the N/O x N/H correlation and model
Groenewegen and de Jong (1994)
figure 7b
Nitrogen: the N/O x N/H correlation and model

24. Nitrogen: the N/O x N/H correlation and model
Groenewegen and de Jong (1994)
figure 7c
Nitrogen: the N/O x N/H correlation and model

25. 3. Distance-independent correlations
3.4 Correlations with He
N/O and N/H correlations with He/H have been observed for PN in the three systems. These relations can be used to compare our abundances with the presumably more correct ISO abundances by Pottasch et al. (IAU Symposium 209, p. 353, 2003). We also compare these correlations with recent models and the ISO sample by Marigo et al. (Astron. Astrophys. 409, 619, 2003). We conclude that the same correlations are obtained, with a slightly larger dispersion.

26. Helium: the N/O x He/H correlation
figure 8a
Helium: the N/O x He/H correlation

27. Helium: the N/O x He/H correlation
figure 8b
Helium: the N/O x He/H correlation

28. Helium: the N/O x He/H correlation
figure 8c
Helium: the N/O x He/H correlation

29. Helium: the N/O x He/H correlation
figure 8d
Helium: the N/O x He/H correlation

30. Marigo et al. (2003) ISO sample (filled squares)
figure 8e
Marigo et al. (2003) ISO sample (filled squares)

31. Marigo et al. (2003) ISO sample (filled squares)
figure 8f
Marigo et al. (2003) ISO sample (filled squares)

32. Marigo et al. (2003) ISO sample – model predictions
figure 9a
Marigo et al. (2003) ISO sample – model predictions

33. Marigo et al. (2003) ISO sample – model predictions
figure 9b
Marigo et al. (2003) ISO sample – model predictions

34. Marigo et al. (2003) ISO sample – model predictions
figure 9c
Marigo et al. (2003) ISO sample – model predictions

35. Helium: the N/H x He/H correlation
figure 10a
Helium: the N/H x He/H correlation

36. Helium: the N/H x He/H correlation
Pottasch et al. (2003)
Sun and Orion
figure 10b
Helium: the N/H x He/H correlation

37. Marigo et al. (2003) ISO sample - model predictions
figure 10c
Marigo et al. (2003) ISO sample - model predictions

38. Helium: the N/H x He/H correlation
figure 10d
Helium: the N/H x He/H correlation

39. Helium: the N/H x He/H correlation
figure 10e
Helium: the N/H x He/H correlation

40. 4. Anticenter PN: the radial gradient
Recently, Costa, Uchida and Maciel (A&A, in press 2004) have analyzed a sample of PN located in the galactic anticenter. It was shown that the observed radial O/H gradient tends to flatten out for large galactocentric distances, roughly R > 10 kpc, in agreement with previous results by Maciel and Quireza (A&A 345, 629, 1999). Therefore, it is interesting to investigate whether PN in the anticenter direction have abundances similar or larger than LMC/SMC objects.

41. figure 11
The O/H radial gradient for galactic PN Costa, Uchida and Maciel (A&A, in press 2004)

42. Sulphur: the S/H x O/H correlation
figure 12a (same as figure 2)
Sulphur: the S/H x O/H correlation

43. Sulphur: the S/H x O/H correlation
MW: Crosses R < 10 kpc
Empty Squares, R > 10 kpc
figure 12b (same as figure 2, separating inner and outer PN)
Sulphur: the S/H x O/H correlation

44. Sulphur: the S/H x O/H correlation
MW: Crosses R < 10 kpc
Empty Squares, R > 10 kpc
figure 12c (same as figure 2, separating inner and outer PN)
Sulphur: the S/H x O/H correlation

45. Argon: the Ar/H x O/H correlation
MW: Crosses R < 10 kpc
Empty Squares, R > 10 kpc
figure 13a (same as figure 3, separating inner and outer PN)
Argon: the Ar/H x O/H correlation

46. Argon: the Ar/H x O/H correlation
MW: Crosses R < 10 kpc
Empty Squares, R > 10 kpc
figure 13b (same as figure 3, separating inner and outer PN)
Argon: the Ar/H x O/H correlation

47. 5. PN in the galactic bulge
Several of the correlations shown are also obeyed by galactic bulge PN, as recently shown by Escudero, Costa and Maciel (A&A 414, 211, 2004).

48. figure 14
The S/H x O/H correlation for galactic bulge PN Escudero, Costa and Maciel (A&A 414, 211, 2004).

49. figure 15
The Ar/H x O/H and Ne/H x O/H correlations for galactic bulge PN Escudero, Costa and Maciel (A&A 414, 211, 2004).

50. figure 16
The N/O x O/H anticorrelation for galactic bulge PN Escudero, Costa and Maciel (A&A 414, 211, 2004).

51. figure 17
The N/H x O/H correlation for galactic bulge PN Escudero, Costa and Maciel (A&A 414, 211, 2004).

52. Extra-galactic Planetary Nebulae Workshop Garching, May 2004
With thanks to:
J. A. de Freitas Pacheco L. G. Lago M. M. Uchida A. V. Escudero
THE END