The population of planetary nebulae Letizia Stanghellini National Optical Astronomy Observatory

Good probes of stellar populations Planetary nebulae (PNs) are the gaseous remnants from the evolution of common stars (M ZAMS ~1-8 M o ) They are observed in many galaxy types, and in the intra-cluster They are easily detected and identified, thanks to their unique spectra Their luminosity function (PNLF) has a sharp high luminosity cutoff, used as secondary distance scale indicator

Caveats Advances to understand PN evolution have been hindered by: –Difficulty of using Galacic PNs as templates (distances poorly known, selective reddening) –Double nature of PNs (PNs and central stars (CSs) should be modeled together!)

To circumvent the problematic Galactic PN distances and reddened disk population, ~10 yr ago we initiated a thorough study of the Magellanic Cloud PNs and their central stars they are: –Absolute probes of stellar evolution through the AGB and beyond –Benchmarks for extragalactic PN populations Modeling of stars and nebulae together, and synthesis of PN population, are also pursued

Open questions and hot issues 1.Nebular asphericity (i.e. bipolarity), origins, evolution, and its correlations with population 2.PNs as probes of elemental enrichment 3.PNs as probes of the initial mass- final mass relation 4.The transition time 5.The astrophysics of the PNLF 6.Intra-cluster (IC) PNs as probes of the IC starlight

PN morphology and stellar pops Morphology depends on the formation and dynamic evolution of the PN, on the evolution of the central star and of the stellar progenitor, and on the environment Galaxy: aspheric PNs associated with higher CS masses, higher N, lower C, lower Galactic latitude than spherical PNs  higher mass progenitors Statistics in Galaxy biased by selective absorption We observed ~100 LMC and ~35 SMC PNs with STIS/HST

_4861 H  _4959 [O III]_5007 [O III] _6300 [O I] 6584 [N II]6563 H  6548 [N II] 6732 [S II]6716 [S II] STIS Slitless Spectra of LMC SMP 16 G430M (4818 — 5104) and G750M (6295 — 6867)

Morphology distribution LMCSMC Round R29 %35 % Elliptical E17 %29 % Round, elliptical46 %64 % Bipolar B34 %6 % Ring BC17 %24 % Bipolar, ring (aspheric) 51 %30 % Point-symmetric3 %6 %

Physical origin of the equatorial disks Stellar rotation- Maybe associated with Strong magnetic field Garcia-Segura 97 Observational ties with WDs Wickramasinge & Ferrario 00 Binary evolution of the progenitor (CE) Morris 81; Soker 98

Mass loss, metallicity, and dust Aspheric PNs are rare in low metal environment (SMC) Superwind forming PNs is activated by radiation pressure on the dust grains, but may also operate in the absence of grains (less efficiently, Willson 04)  are spherical and aspheric PNs created by different superwind mechanisms? Spitzer SED in LMC and SMC PNs will allow more insight on dust compounds and superwind mechanisms

PNs as probes of stellar evolution Low- and intermediate-mass stars enrich the ISM through the RGB, AGB, PN phases Stars that go through the AGB may be the principal producers of nitrogen, and supply as much carbon as massive stars Net result: C (in particular from M TO 3.5 stars) enrichment of ISM Evolution on the TP-AGB and beyond is still controversial. Comparing evolutionary yields to PN composition is essential

Carbon in LMC PNs ~350 PNs LMC known Jacoby 04 To date, only ~20 UV spectra, 10 carbon determination Leisy & Dennefeld 97 We acquired HST/STIS G140L and G230L UV spectra and determine carbon abundance for an additional 24 LMC PNs

Optical and UV morphology C III]1908 C II] 2327 [Ne IV] 2426 nebular continuum LMC SMP 95 Broad band [O III] 5007 [N II] H  [N II] Stanghellini, Shaw, & Gilmore 05

Extracted 1D spectra, G140L SMP 19 SMP 48 SMP 81

Extracted 1D spectra, G230L SMP 19 SMP 48 SMP 81

Models Stellar evolution, 1< M i < 8 M o Z=0.008 CNO total and final yields –Synthetic models, new opacity: Marigo 01 (VW95 dM/dt); van den Hoek & Groenewegen 97 (Reimers dM/dt) –Forestini & Charbonnel 97, and Karakas 03 do not offer final yields

High mass models yield higher C/O and N/O than observed in LMC PNs  round  elliptical  ring bipolar l point-symmetric  unknown morphology Stanghellini et al. 05

N/O and C/O over-predicted (especially for aspheric LMC PNs) Possible explanations 1- INITIAL COMPOSITION Evolutionary models M01 and HG97 get initial CNO abundances scaling according to Y from solar. Resulting abundances much higher than observed in LMC HII regions and SNR Dennefeld 89; Russel & Dopita 92  Log (N/O) HG97 ZAMS - obs ≤ 0.5  Log (C/O) HG97 ZAMS - obs ≤ 0.6 (Karakas 05 uses observed initial composition, but does not give final yields)

2- BINARY EVOLUTION From Izzard & Tout 04 yield (binary evolution)/ yield (single star ev.) C 0.86 N 0.69 O HIDDEN CARBON Carbonaceous dust CO and other molecules in aspheric PNs Josselin et al. 00

The astrophysics of the PNLF –Origin of double-peak –Effects of metallicity: use LMC and SMC PNs –Nature of PNs at the high luminosity cutoff Jacoby & De Marco 02

Stellar evolution and the PNLF Montecarlo synthetic CS population N(M TO )  M TO adapted from Stanghellini & Renzini 00

Observed distributions of I(5007)/I(Hb) LMC SMC

Metallicity and PN output Galaxy LMC SMC

Galaxy LMC PN cooling in different galaxies Our HST data: LMC =9.4 (3.1) =5 (5) SMC =5.7 (2.5) UV: Cycle 13 Stanghellini et al. 02, 05

Central stars in the SMC PNLF SMC

Intra-cluster (IC) PNs Do PNs survive in the IC medium? What is their energy output? Compared to galaxian PNs? How long do they live? Inferred IC starlight Villaver & Stanghellini ApJ in press

Modeling the IC AGB to PN evolution M TO = 1 M o Galactic PN metallicity Superwind, post-AGB wind, and evolutionary track from Vassiliadis & Wood 94, 95 Hydrodynamic model by Villaver et al. 02 IC conditions as in Virgo –v=10 3 [km s -1 ] Arnaboldi et al. 04 –T=10 7 [K] Takano et al. 89 –N=10 -3 [cm -3 ] Fabricant & Gorenstein 83

Evolution and survival of AGB and post-AGB phases in the IC (times: yr, from AGB onset) : bow shock visible : second TP : PN forms

Intensity profile of IC PN Dots: IC PN, t tr =1000 yr Solid line: galaxian PN, t tr =1000 yr Broken line: galaxian PN, t tr =0

IC PN duration and IC starlight We infer a lifetime between 5000 and yr We use the FCT Renzini & Buzzoni 86 to derive the luminosity-specific PN density:  = N PN / L T = B t PN ≤ 2.0 * [PN L o -1 ] (upper limit comparable to Durrell et al. 02)   * ≤   ≤ 4.8 * [PN L o -1 ] Using Aguerri et al. 05 counts of IC PN in Virgo we estimate the fraction of IC starlight:  [IC/total] Virgo core = %

Present/future PN ejection mechanism: dust and chemistry: LMC and SMC PNs SED with Spitzer - Cycle 2 Carbon and stellar evolution: Cycle 13 ACS/HST UV spectra with prisms to get SMC PN carbon Use pop-synthesis and LMC/SMC PNLF as templates to study the physics of PNLF Extend CS+PN models to other masses