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Surveys for Planetary Nebulae in the Magellanic Clouds

This study focuses on surveys of Planetary Nebulae (PN) in the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC), exploring stellar and galaxy evolution. Various survey techniques are employed, from direct imaging to high-resolution spectroscopy, to unveil properties such as chemical composition and expansion dynamics. Challenges in surveying PN, including contamination and nomenclature issues, are addressed. The study aims to provide a comprehensive understanding of PN populations in the Magellanic Clouds and their implications on stellar evolution.

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Surveys for Planetary Nebulae in the Magellanic Clouds

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  1. Surveys for Planetary Nebulae in the Magellanic Clouds LMC SMC Where we simultaneously study stellar and galaxy evolution

  2. Orientation The View from Cerro Tololo SMC MW LMC

  3. Relationship to MW HI map from Putnam et al (2003) Magellanic Stream extends >90° across sky, but has few stars Distances: accurate to ±10% 50 kpc to LMC* 62 kpc to SMC *depth within LMC ±3%

  4. Extent of LMC: van de Marel 2001 SMP 78 24° 22° RGB and AGB counts indicate the LMC subtends ~130 sq. deg.

  5. Common Survey Techniques • To identify PN candidates via • Direct imaging through filters (on-band and off-band) • Objective prism imaging (historically photographic) • Spectral “imaging” (PN Spectrograph) • Other kinds of surveys • Follow-up High resolution imaging (HST, AO systems) • Follow-up spectroscopy • Candidate verification • Chemical composition • Central star atmospheric properties • Kinematic probe of host galaxy properties: dark matter? • Kinematic probe of nebula itself: expansion properties

  6. “Modern” SMC Surveys *Magellanic Cloud Emission Line Survey

  7. Technology Helps The Clouds are easy targets with large format CCD mosaic cameras on large telescopes ESO 2.2m CTIO 4m Example: MB 233 – but, probably not a PN CTIO 4m extends ~1 mag beyond ESO 2.2m

  8. SMC Completeness • Most Recent Surveys • Jacoby & De Marco (2002) • 10 fields of 0.5° each (2.2M) • Depth of ~6 mags • Jacoby & De Marco (in prep) • 6 fields, 3 new PN (CTIO 4m) • Depth of ~7 mags • Not very productive • more depth doesn’t help • outer fields have few PN 2+1 +1 3 2 5 6 2 +2 5 12 7 4 7 8

  9. “Modern” LMC Surveys *Candidates to be verified

  10. “Modern” LMC Surveys The pioneering surveys by Henize (1956), Lindsay (1961), Henize & Westerlund (1963), Lindsay & Mullan (1965), and Westerlund & Smith (1964) defined the extragalactic PN field. *Candidates to be verified

  11. LMC Completeness • Most Recent Surveys • Reid & Parker (in prep) • 25 sq.deg.; 1000 candidates • Photographic H stacked • Leisy et al(in prep) • Many fields & new PN (2.2m) • Jacoby & De Marco (in prep) • 1 field, 10 new PN (4m) • Depth of ~7 mags 5+10

  12. The Clouds are a Special Place • Nearest (by 10X) large population of EG PN (50-70 kpc) • Distances known: 50 and 62 kpc (common for each sample) • Faintest PN are observable (unbiased statistical sample) • Central stars can be studied directly (photometry, spectra) • Masses for low-metallicity initial-to-final mass relation • Identify binaries via velocity variations • PN are easily resolved: from space or with AO facilities • Morphology • Physical radii allow expansion ages to be measured • High S/N spectroscopy allows studies for • Compositional analysis across full luminosity range • Internal dynamics • Large samples: hundreds of PN can be studied • Low/Intermediate metallicity sample

  13. Challenges for MC PN Surveys • Contaminants in surveys • Compact HII regions, especially if low surface brightness • Novae (2 “PN” in SMC, 1 in LMC) • Background emission-line galaxies • Faint nebulae are extended  detection shifts from point source domain to surface brightness problem • Very large area on sky • SMC: ~ 20 sq. deg. • LMC: ~130 sq. deg.

  14. Challenges for MC PN Surveys • Confirmation and follow-up spectroscopy compromised by • Crowding from stars • Diffuse HII emission • Nomenclature (Parker, Cibis) • Surveys began without naming convention • We have near-chaos today • Accurate coordinates – objects may be extended 5-10 arcsec

  15. Galaxy Cluster Behind SMC Field 11 [OIII] Diff HST image of MA 1682

  16. Spectroscopy is Complicated CTIO 4m spectrum of JD-17: H+[NII]+[SII] region Raw Sky subtracted • Issues remain: • Incomplete subtraction from diffuse HII emission • Stellar spectra from background • Nebula resolves, so some flux falls off slit • Faintest PN will be lost in the stellar continuua • But, see Roth for instrumental solution

  17. SMC Luminosity Function • Survey extends 8 mags down PNLF • Dip seen in PNLF for first time • Absent in models, generally • Possibilities (Marigo/Girardi models) • Progenitors from multiple ages (<1 and 8-10 Gyr) • Binary stars in old pops (common envelope evolution) • Hints from M33 • Age?, metallicity?, IMF?

  18. How Many PN are There? • Technically feasible to survey the SMC and LMC to the faintest PN and find them all, rather than extrapolate • A “Complete” survey is “defined” to go 8 mags down LF • SMC surveys are largely complete to ~7 mags  1.5X more • LMC surveys are largely complete to 5 mags  3X more Currently known, entire SMC 84 With deeper survey (8 mags) 120-170 Currently known, entire LMC 350* With deeper survey (8 mags) 800-900 *sample is neither homogeneous in depth nor spatially complete; Reid and Parker survey will improve statistics significantly.

  19. Questions That MC PN Can Answer • How many PN are in the Clouds, how do the counts compare to galaxy evolution models, & what are inferences for other galaxies? • Tests stellar and galaxy evolution theory, population mixes • Need to complete the surveys • Need follow-up spectra to confirm candidates • What fraction of PN have binary CS? Maybe all of them ??? • De Marco et al (2004) – 11/12 Galactic PN are velocity variables • Need synoptic spectroscopy of PN CS at moderate resolution • Velocities of Cloud PN can be accurate to 1 km/s – with forthcoming large samples, can we map the dark matter? • Need spectroscopy of nebulae at moderate resolution • Need kinematic models of the SMC and LMC (with GCs, HII, stellar velocities)

  20. Questions That MC PN Can Answer • What is the distribution of central star masses, and what is the initial-to-final mass relation as a function of metallicity? • Need medium resolution spectroscopy of central star and nebula • Do the brightest PN have the characteristics (CS mass, T*, L*, nebular age/size) predicted by PNLF models (e.g., Marigo et al) • Need specific model predictions • Need statistically complete HST (or ground AO) measurements of nebula (plus above bullet)

  21. Astrophysics from Cloud PNat this conference • Stanghellini – HST observations of ~half the Cloud PN allow morphology of many PN to be studied in absolute terms (radius, age, shape, kinematics) to link to their progenitor stars • Villaver, Arrieta – MV, T*, L*, mass, composition now can be measured directly for many central stars (from spectra)  IFMR • Shaw – 100 LMC & 30 SMC PN with HST imaging allow correlations of physical properties to explore formation and evolutionary processes of PN that are not possible elsewhere • Reid – complete surveys are possible to faintest PN for accurate counts, PN birth rates, tests of stellar evolution models • Maciel – Composition correlations in SMC, LMC, and MW • Peña – Detailed study of N66 in LMC • Tsammis – Recombination and forbidden line analysis in SMC

  22. Conclusions • Easy to find many PN in Clouds with current methods – this is the only large sample where all PN can be found! • SMC surveys are approaching completeness • LMC surveys could be complete soon (Reid & Parker, Leisy et al) • Deficit at 2-4 mags in PNLF is a clue to stellar population content – need models that interpret this feature! Compare in LMC. • Almost any kind of PN study can be done better in the Clouds (distances known, spatially resolved, relatively bright) Confrontation of observations and theory (Ciardullo/Girardi talks) may be solved, in part, with observations of Cloud PN • Models predict properties of bright PN and CS – test them! • Cloud PN derive from a range of metallicities and progenitor ages, the principal parameters driving the model PNLF cut-off

  23. END I have never in my life learned anything from anyone who agreed with me. Dudley Field Malone

  24. Stellar Abundances in the SMC • Stars in SMC are diverse (Larson, Clausen, Storm 2000) • From Stromgren photometry of fields stars in SMC

  25. Are Faint PN Different From Bright PN?Consider SMC … • 1 (5.5% of 18) of SMP PN have [NII]/H > 1 • 7 (28% of 25) new Jacoby & De Marco PN have strong [NII] • Fraction of PN with [NII]/H > 1, in bright (<2 mags) and intermediate (<6 mags) luminosity groups • LMC ratio = 1.9 (16% vs 31%) • SMC ratio = 4.3 (6% vs 26%) • Type I PN in SMC are preferentially faint • They generate more dust (Ciardullo & Jacoby 1999) • Their central stars are massive and fade fast

  26. [NII]/H Ratios: PN 1 – 9 1 1 4 7 1 1 2 5 8 3 6 9

  27. [NII]/H Ratios: JD 10 – 18 10 13 16 11 14 17 12 15 18

  28. [NII]/H Ratios: PN 19 – 25 19 22 25 20 23 Nova 21 24

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