Garching, 19/05/20041 Modelling the PNLF: Population Effects on the Bright Cut-off 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

Garching, 19/05/20042 Ciardullo, Jacoby, et al.’s interpretative scenario: I.Jacoby (1996): narrow CSPN mass distribution (0.58 ± 0.02 M  ) over the age range 3-10 Gyr, i.e. initial mass range 1-2 M . II.Ciardullo & Jacoby (1999) : circumstellar extinction estinguishes the overluminous and massive-progenitor PNe below the cut-off. III.Dopita et al. (1992) explains little dependence on metallicity. Why is the PNLF cut-off magnitude constant? So far no robust theoretical explanation I.Dopita et al. (1992), Mendez et al. (1993) predict a strong dependence on population age. I.Modelling full of hidden and implicit assumptions, rarely a population synthesis approach. but

Garching, 19/05/20043 Synthetic model of PN evolution AGB evolution (Marigo et al. 1996,1998, Marigo 2001)  central star mass (Mi, Z) [p][p]  AGB wind velocity  density and chemical comp. of the ejecta (r, t) post-AGB evolution (Vassiliadis & Wood 1994)  logL-logT eff tracks (H-burn./He burn.) [p1] [p2][p1][p2]  fast wind dynamical evolution of the nebula  interacting-winds model [p][p]  shell thickening due to ionisation Ionisation and nebular emission lines  CLOUDY photoionisation code [p1] [p2][p1][p2] (Marigo et al. 2001, A&A, 378, 958)

Garching, 19/05/20044

5 Vassiliadis & Wood (1994) Initial masses: 0.9 – 5.0 M  Metallicities: Z= 0.016, 0.008, 0.004, H-burning central stars He-burning central stars  loops  less luminous  longer evolutionary timescales post-AGB evolutionary tracks

Garching, 19/05/20046 Interacting-winds model (Volk & Kwok 1985; Kahn 1983; Breitschwerdt & Kahn 1990) I. MOMENTUM-DRIVEN PHASE I. ENERGY-DRIVEN PHASE radiative cooling > kinetic energy from the fast wind Isothermal shock (R I  R S ) radiative cooling << kinetic energy from the fast wind Formation of the hot bubble Adiabatic shock (R I << R S ) (eqs)(eqs)

Garching, 19/05/20047 Ionisation and line emission from CLOUDY (Ferland 2000, 2001) INPUT Expanding-sphere geometry Rin, Rout Uniform N(H) Elemental abundances (H,He,C,N,O,etc.) L and Teff of the CSPN Mi=2.0 M  ; M CSPN =0.685 M  ; Z=0.008; H-burn.; Mion=0.091 M  ; t PN =3000 yr OUTPUT Te (volume average) ionisation fractions line fluxes

Garching, 19/05/20048 Mi=1.7 M  ; M CS = 0.6 M  ; Z=0.019 Output of the PN synthetic model Time evolution of: Ionised mass Nebular radius Expansion velocity optical configuration emission line luminosities

Garching, 19/05/20049 NUCLEAR BURNING REGIME (H-/He-burning tracks) TRANSITION TIME (500 to yr) METALLICITY (Z=0.019, 0.008, 0.004) STAR FORMATION HISTORY (mainly the age of last episode of SF) FREE PARAMETERS Monte Carlo + population synthesis of galaxies used to simulate PN samples for any distribution of parameters

Garching, 19/05/ PN central stars in the HR diagram Simulated PN sample: M 5007 < 1 ; N tot = 500 SFR=const.; Z=0.019; t tr =500 yr H-burn. and He-burn. tracks  optically thick ;  optically thin

Garching, 19/05/ Ionised mass-radius relation Observed data from Zhang (1995), Boffi & Stanghellini (1994) Simulated PN sample: M 5007 < 1 ; N tot = 500 SFR=const.; Z=0.019; t tr =500 yr H-burn. and He-burn. tracks  optically thick ;  optically thin

Garching, 19/05/ Electron density-radius relation Data from Phillips (1998) Simulated PN sample: M 5007 < 1 ; N tot = 500 SFR=const.; Z=0.019; t tr =500 yr H-burn. and He-burn. tracks  optically thick ;  optically thin

Garching, 19/05/ Electron temperature distribution of Galactic PNe Observed (ESO-Strasbourg Catalogue) Predicted (H-burning tracks) Predicted (He-burning tracks)

Garching, 19/05/ I([OIII] 5007)/I(H  ) distribution of Galactic PNe Observed (McKenna et al. 1996) Predicted (H-burning tracks) Predicted (He-burning tracks)

Garching, 19/05/ WHICH PNe FORM THE CUT-OFF? M CSPN  M  ; M i  2-3 M  ; age  Gyr

Garching, 19/05/ DEPENDENCE ON H-/He-BURNING TRACKS 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/ 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/ 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/ 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/ PNLF IN TEMPLATE GALAXIES t   t t t Z Z SFHAMR

Garching, 19/05/ M 5007  -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 M CSPN 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) MAIN CONCLUSIONS