1. THE INNER ABUNDANCE GRADIENT OF M33 USING BRIGHT PLANETARY NEBULAE
THE INNER ABUNDANCE GRADIENT OF M33 USING BRIGHT PLANETARY NEBULAE
Grażyna Stasińska LUTH Observatoire de Paris Meudon
José Vilchez, Enrique Perez, Rosa Gonzalez Delgado IAA Granada
Romano Corradi, Antonio Mampaso IAC Tenerife
Laura Magrini DASS Florence

2. Giant HII regions start the saga of abundance gradients in M
giant HII regions were the first indicators of abundance gradients in spiral galaxies
easily observed
easily interpreted
if Te can be determined eg from [OIII]4363/5007
ionic abundances from line intensity ratios:
O++/H+ = ([OIII]5007/Hb) / (e[OIII](Te)/eHb(Te))
elemental abundances
adding observed ions
O/H = O+/H+ + O++/H
or using icfs
(e.g. Ne/O = Ne++/O++)
if Te cannot be measured directly (i.e. if only “strong lines” are measured)
abundances derived using “statistical methods” calibrated on photoionization models of HII regions or on observations of GHRs with measured Te

3. Giant HII regions start the saga of abundance gradients in M
O/H
combination of results from
Vilchez et al 1988
Kwitter & Aller 1981
Smith 1975
N/H

4. other ways to determine abundance gradients in spiral galaxies
stellar clusters Ma, Zhou, Chen 2004
not robust abundances determinations
probe wide range of ages
B supergiants Monteverde et al 1997, 2000
difficult to observe, still few points
analysis through complex modelling
supernovae Smith et al 1993
not robust abundance determinations
AGB stars Cioni ( this conference)
calibrated on HII region abundances(Cook et al 1986)
or on stellar population evolutionary models(Mouhcine & Lançon 2003)
planetary nebulae our work
difficult to observe (eg Roth et al 2004) but robust abundance determinations

5. what is wrong with HII regions? ........................................ .................. ... ...
in the central parts of spiral galaxies the metallicity is supposedly high
although the gradients could also flatten (Smartt et al 2001)
or even become inverted (Gorny & Stasińska 2004)
at high metallicities
metal cooling depresses the electron temperature
and the weak [OIII]4363 line is not observed
one has to rely on “strong line” methods
the derived values of O/H strongly depend
on the calibration used (Pindao et al 2002)
Observations with Very Large Telescopes cannot help:
even if [OIII]4363 is measured
the derived O/H will be underestimated
since strong Te gradients due to cooling by [OIII] 52, 88m
make [OIII]4363/5007 overestimate Te in the emitting zones

6. the advantage of using extragalactic PNe
useful spectroscopy can be done only on luminous PNe
evolution of PNe
in the( L[OIII] vs nH )
and (L[OIII] vs T* diagrams)
for different central star masses
____ M* = 0.58 M
____ M* = 0.60 M
____ M* = 0.62 M
____ M* = 0.64 M
luminous PNe have high nH and high Teff (>100000K) during a large fraction of tlife
both factors increase Te with respect to giant HII regions
and eliminate the bias in the determination of O/H (Stasińska 2000)
Giant HII region
high luminosity PN

7. What is probed by the chemical composition of luminous PNe?
most luminous PNe
have central star masses of ~0.64Mo
are descendent of stars with initial masses of ~3 M
their Ne, Ar, S abundances are expected to be the same as those of the ISM out of which the progenitors were formed about 1 Gyr ago
initial-final mass relation
their oxygen abundances might be slightly affected by mixing processes in the progenitors
(if the initial metallicity is smaller than 1/4 solar)

8. our observations of PNe in M33 ........................................ .................. ... ...
Magrini et al. (2000; 2001)

9. our observations of PNe in M33 ........................................ .................. ... ...
planned observations: 10 bright PNe in the inner disk of M33
due to weather conditions only 4 PNe were observed
Observations were performed using the ISIS spectrograph attached to the WHT4.2m of the ORM in La Palma (Canary Islands) during the night 28 Oct 2003.
The exposures were of 3 hours per spectrum
Both, blue and red arms were
used with a dichroic set to an effective wavelength of 5400 A.
The slit width was set to 1.5 arcsec and the seeing oscillating
between 1.2 to 1.6 arcsec.
The grating R600B was used in the blue arm, centered at 4400 A
yielding a reciprocal dispersion of  0.45 A/pix ; the grating R300R
was used in the red arm centered at 6130 A yielding a dispersion of
 0.84 A/pix.

10. our spectra
detected lines
H Balmer lines, HeI, HeII, [OII]3727, [OIII]4959, 5007, [OIII]4363, [NeIII]3869, [NII]6585, [SII]6716, 6731, [Ar III] 7135
problems
subtraction of the diffuse emission
stellar absorption lines

11. very preliminary abundances (do not quote!)
the abundances of our PNe appear to be well below solar!
Te[OIII] O/H Ne/H
(x10-6) (x10-6)
PN 7a
PN 7b
PN 10a
PN 10b < > >1300
solar
problems with our PNe spectra
subtraction of the diffuse emission
stellar absorption lines

12. very preliminary abundances (do not quote!)
the abundances of our PNe appear to be well below solar!
is this real ?
our PNe sees to indicate the same as the Ne abundances obtained from ISO measurements of giant HII regions by Willner & Nelson-Patel 2002
filled symbols: Ne/H from ISO (no Te dependance, no icf needed)
open symbols: O/H (optical data)
problems with our PNe spectra
subtraction of the diffuse emission
stellar absorption lines

13. Planetary Nebulae as Astronomical Tools Gdańsk (Poland) 28 June - 2 July Grażyna Stasińska and Ryszard Szczerba (co-chairs)
Planetary Nebulae as tests of stellar evolution theories
Planetary Nebulae as tests of stellar nucleosynthesis theories
Planetary Nebulae as tests of stellar atmosphere models
Planetary Nebulae as tests of atomic physics
Planetary Nebulae as test of photoionization models
Planetary Nebulae as tests of radiation hydrodynamics
Planetary Nebulae and progenitors as sites of cosmic dust formation
Planetary Nebulae as constraints for models of chemical evolution of galaxies
Planetary Nebulae to determine the total masses of galaxies
Planetary Nebulae to detect stellar populations in the intergalactic space
Planetary Nebulae to test dynamical evolution/build up of galaxies
Planetary Nebulae as cosmological candles
Planetary Nebulae as a subject for public outreach