The population of planetary nebulae

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The population of planetary nebulae

• Letizia Stanghellini
• National Optical Astronomy Observatory

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Good probes of stellar populations

• Planetary nebulae (PNs) are the gaseous remnants
  from the evolution of common stars (MZAMS1-8
  Mo)
• 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

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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!)

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• 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

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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

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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

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STIS Slitless Spectra of LMC SMP 16 G430M
(48185104) and G750M (62956867)
_4959 O III
_5007 O III
_4861 Hb
_6300 O I
6584 N II 6563 Ha 6548 N II
6732 S II 6716 S II
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Morphology distribution
LMC SMC
Round R 29 35
Elliptical E 17 29
Round, elliptical 46 64
Bipolar B 34 6
Ring BC 17 24
Bipolar, ring (aspheric) 51 30
Point-symmetric 3 6
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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

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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

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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 MTOlt3.5 stars)
  and N (especially from MTOgt3.5 stars) enrichment
  of ISM
• Evolution on the TP-AGB and beyond is still
  controversial. Comparing evolutionary yields to
  PN composition is essential

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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

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Optical and UV morphology
Broad band O III 5007 N
II Ha N II

C III1908 C II 2327
Ne IV 2426 nebular continuum

LMC SMP 95
Stanghellini, Shaw, Gilmore 05
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Extracted 1D spectra, G140L
SMP 19
SMP 48
SMP 81
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Extracted 1D spectra, G230L
SMP 19
SMP 48
SMP 81
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Models

• Stellar evolution, 1lt Mi lt 8 Mo Z0.008
• 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

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• High mass models yield higher C/O and N/O than
  observed in LMC PNs
• ? round
• ? elliptical
• ? ring
• ? bipolar
• point-symmetric
• ? unknown morphology

Stanghellini et al. 05
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• 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
• D Log (N/O)HG97 ZAMS - obs 0.5
• D Log (C/O)HG97 ZAMS - obs 0.6
• (Karakas 05 uses observed initial composition,
  but does not give final yields)

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• 2- BINARY EVOLUTION
• From Izzard Tout 04
• yield (binary evolution)/ yield (single star
  ev.)
• C 0.86
• N 0.69
• O 1.0
• 3- HIDDEN CARBON
• Carbonaceous dust
• CO and other molecules in aspheric PNs Josselin
  et al. 00

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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
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Stellar evolution and the PNLF
Montecarlo synthetic CS population
N(MTO)?MTO-2.35
adapted from Stanghellini Renzini 00
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Observed distributions of I(5007)/I(Hb)
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Metallicity and PN output
Galaxy LMC SMC
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PN cooling in different galaxies
Our HST data LMC ltI(5007)/I(Hb)gt9.4
(3.1) ltI(1909)/I(Hb)gt5 (5) SMC ltI(5007)/I(Hb)gt5
.7 (2.5) UV Cycle 13
Stanghellini et al. 02, 05
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Central stars in the SMC PNLF
SMC
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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

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Modeling the IC AGB to PN evolution

• MTO 1 Mo
• 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
• v103 km s-1 Arnaboldi et al. 04
• T107 K Takano et al. 89
• N10-3 cm-3 Fabricant Gorenstein 83

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Evolution and survival of AGB and post-AGB phases
in the IC (times yr, from AGB onset)
2.8 105 bow shock visible
3.3 105 second TP
4.14 105 PN forms
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Intensity profile of IC PN
Dots IC PN, ttr1000 yr Solid line galaxian PN,
ttr1000 yr Broken line galaxian PN, ttr0
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IC PN duration and IC starlight

• We infer a lifetime between 5000 and 10 000 yr
• We use the FCT Renzini Buzzoni 86 to derive the
  luminosity-specific PN density
• a NPN / LT B tPN 2.010-7 PN Lo-1
• (upper limit comparable to Durrell et al. 02)
• ? 2.410-9 a1.0 4.810-9 PN Lo-1
• Using Aguerri et al. 05 counts of IC PN in Virgo
  we estimate the fraction of IC starlight
• ? IC/totalVirgo core 7 - 15

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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 CSPN models to other masses

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Happy birthday Alvio!