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Spectroscopy of PNe in Sextans A, Sextans B, NGC 3109 and Fornax

A.Y. Kniazev (MPIA), E.K. Grebel (Basel), A.G. Pramskij, S.A. Pustilnik (SAO RAS). Spectroscopy of PNe in Sextans A, Sextans B, NGC 3109 and Fornax. PNe ESO Workshop. 20 May 2004. Introduction. PNe with their prominent emission lines can be used to measure metallicity in nearby galaxies

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Spectroscopy of PNe in Sextans A, Sextans B, NGC 3109 and Fornax

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  1. A.Y. Kniazev (MPIA), E.K. Grebel (Basel), A.G. Pramskij, S.A. Pustilnik (SAO RAS) Spectroscopy of PNe in Sextans A, Sextans B, NGC 3109 and Fornax PNe ESO Workshop 20 May 2004

  2. Introduction • PNe with their prominent emission lines can be used to measure metallicity in nearby galaxies • Together with HII regions PNe provide a probe of the chemical enrichment and star formation history of a galaxy • In spite of the importance of the topic for PNe in extermal galaxies, only few spectroscopic data have been obtained ESO Workshop 20 May 2004

  3. Observations • Some PNe and HII in 3 dIrr galaxies which form a small group just beyond the Local Group (D ~ 1.3 Mpc) and PN in the Local Group Fornax dwarf spheroidal galaxy (D ~ 140 kpc) • NTT, 2003-2004 as a backup block for the main program “Toward Establishing a Complete Sample of Low Surface Brightness Galaxies” • Red EMMI channel, Grisms #5 (3900-6800 Å, 1.6 Å/pix), #6 (5700-8500 Å, 1.4 Å/pix) • Seeing was in the range 0.4" – 0.6" and slit = 2" ESO Workshop 20 May 2004

  4. Reduction • MIDAS + IRAF • Method of emission line measurements and calculation of abundances was described in detail in Kniazev et al. (2004, astro-ph/0404133) [Strong Emission Line HII Galaxies in the Sloan Digital Sky Survey] ESO Workshop 20 May 2004

  5. PN in Fornax Spectroscopy was published by Danziger et al. (1978) and by Walsh et al. (1997) (without [OIII] λ4363 Å line).

  6. PN in Fornax Maran et al. (1984) Our He 11.08 10.98 ± 0.03 N <7.5 7.06 ± 0.03 O 8.4 ± 0.12? 8.28 ± 0.03 Ne 7.6 7.45 ± 0.05 Ar 5.9 6.08 ± 0.03 S <6.7 6.45 ± 0.05 -3 Electron number density = 750 cm Conclusion: The new abundance determinations with much better accuraces are well consistent with old ones.

  7. PN Candidates in NGC 3109 PN candidates in NGC 3109 were taken from Richer & McCall (1992) ESO Workshop 20 May 2004

  8. PN Candidates in NGC 3109 PN1: 12 + log(O/H) = 7.50 ± 0.04 PN2: 12 + log(O/H) = 7.58 ± 0.04 HII: 12 + log(O/H) = 7.65 ± 0.06 PN4: 12 + log(O/H) = 7.78 ± 0.09 PN5: 12 + log(O/H) = 7.71 ± 0.04 HII: 12 + log(O/H) = 7.72 ± 0.08 Preliminary Conclusions: 1. Oxygen abundances of PNe and HII regions are all in the small range near 12+log(O/H) ~ 7.65 ± 0.1 2. Oxygen abundances for HII is well consistent with previous from Lee et al. (2003) ESO Workshop 20 May 2004

  9. PN Candidate in Sextans A PN candidate in Sextans A was taken from Jacoby & Lesser (1981) and from Magrini et al. (2003) ESO Workshop 20 May 2004

  10. PN Candidate in Sextans A HII(a): 12 + log(O/H) = 7.54 ± 0.09 HII(b): 12 + log(O/H) = 7.54 ± 0.09 (see Kaufer et al. 2004) HII(c): 12 + log(O/H) = 7.56 ± 0.09 PN: 12 + log(O/H) = 7.84 ± 0.06 Preliminary Conclusions: 1. The oxygen abundances of HII regions and the PN are different at high confidence level 2. Factor of ~2 higher metallicity of the PN likely implies unusual evolutionary scenario for the PN progenitor. ESO Workshop 20 May 2004

  11. PN Candidate in Sextans B PN candidates in Sextans B were taken from Magrini et al. (2002) ESO Workshop 20 May 2004

  12. PN Candidate in Sextans B Preliminary conclusions: 1. We spectroscopically confirmed that PN3 candidate in SextansB is PN. 2.At the confidence level of 67% the oxygen abundance of PN3 in SextansB is 12+log(O/H) > 7.3. This is consistent with measured 12+log(O/H) in the two nearby HII regions. ESO Workshop 20 May 2004

  13. Heliocentric Velocities Fornax PN Vel = 129 ± 14 km/s (measured) Fornax Vel = 58 ± 9 km/s (from NED) ESO Workshop 20 May 2004

  14. Diagnostic Diagrams Diagnostic diagrams can separate confidently some of PNe, but significant part of them can be hidden in the region which is more typical for HII regions. ESO Workshop 20 May 2004

  15. Summary • We observed the Fornax PN and 6 PN candidates in the Local Group galaxies Sextans A, Sextans B and NGG3109 • With high quality spectroscopy we confirmed PN nature of all 6 observed candidates • We derived oxygen abundances for the PN and all but one observed PN candidates by direct measurement of Te ESO Workshop 20 May 2004

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