Garching, 19/05/2004 1 Modelling the PNLF: ulation Effects on the Bright Cut- Paola Marigo – Dipartimento di Astronomia,Padova Léo Girardi – Osservatorio Astronomico di Trieste Achim Weiss – Max-Planck-Institut fur Astrophysik, Garching Martin Groenewegen – Instituut voor Sterrenkunde, Leuven Cesare Chiosi – Dipartimento di Astronomia,Padova Abell 39
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Garching, 19/05/20041 Modelling the PNLF: Population Effects on the Bright Cut-off Paola Marigo – Dipartimento di Astronomia,Padova Léo Girardi – Osservatorio.
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Garching, 19/05/2004 1
Modelling the PNLF: Population Effects on the Bright Cut-off
• No dependence for young ages (i.e galaxies with continued SFR)• Strong dependence for old ages• Anyway both H- and He-burning tracks are expected to occur
Garching, 19/05/2004 17
DEPENDENCE ON TRANSITION TIME
• Some dependence for young ages – about 500 yr to reproduce observed cut-off of spirals• No dependence for old ages
Garching, 19/05/2004 18
DEPENDENCE ON METALLICITY
Ciardullo (2002) based on Dopita et al. (1992) photoionisation models
ASSUMPTION: at any Z, age of 0.8 Gyr (of the star at the PNLF cut-off)
6 Gyr
0.8 Gyr
• Not what expected from Dopita et al. (1992) models• Non-monotonic behaviour for young ages – caused by 3rd dredge-up of oxygen in intermediate-mass AGB stars• Monotonic behaviour at old ages (no 3rd dredge-up)
Garching, 19/05/2004 19
DEPENDENCE ON AGE OF THE LAST EPISODE OF SF
• Strong dependence after about 0.7 Gyr• Decline of about 5 mag for 10-Gyr old populations
Garching, 19/05/2004 20
PNLF IN TEMPLATE GALAXIES
t
t t
t
Z
Z
SFH AMR
Garching, 19/05/2004 21
M5007 -4.5 can be reproduced for galaxies with ongoing or recent star formation
difficulty to explain the observed invariance of the cut-off in galaxies from late to early types:
recent burst of SF in ellipticals?
something missing in the models? (yes, but e.g. extinction makes PNe fainter, not brighter)
could larger MCSPN or higher [O/H] at low Z produce such bright PNe at old ages? (under investigation)
some exotic type of PNe in ellipticals? (to be investigated)