1. 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)
20 May 2004
PNe ESO Workshop

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
20 May 2004
ESO Workshop

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, as a backup block for the main program “Toward Establishing a Complete Sample of Low Surface Brightness Galaxies”
Red EMMI channel, Grisms #5 ( Å, 1.6 Å/pix), #6 ( Å, 1.4 Å/pix)
Seeing was in the range 0.4" – 0.6" and slit = 2"
20 May 2004
ESO Workshop

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

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 Conclusion: The new abundance determinations
Maran et al. (1984) Our
He ± 0.03
N < ± 0.03
O ± 0.12? ± 0.03
Ne ± 0.05
Ar ± 0.03
S < ± 0.05
Electron number density = 750 cm -3
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)
20 May 2004
ESO Workshop

8. PN Candidates in NGC 3109 Preliminary Conclusions:
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)
20 May 2004
ESO Workshop

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

10. PN Candidate in Sextans A
HII(a): 12 + log(O/H) = 7.54 ± 0.09
HII(b): 12 + log(O/H) = 7.54 ± (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.
20 May 2004
ESO Workshop

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

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.
20 May 2004
ESO Workshop

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

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.
20 May 2004
ESO Workshop

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
20 May 2004
ESO Workshop