1. Surveys for Planetary Nebulae in the Magellanic Clouds
SMC
LMC
As the nearest major galaxies, this is where EGPN field began 50 years ago
More surveys here than any other external galaxy, but a heterogeneous mix using variety of techniques, depths, spatial completeness
The intent of a survey is to kickstart the astrophysical process – by finding the PN that allow us to study the individual objects and their host galaxies. The survey offers some science return in itself (stellar death rates, distances – if controversial)
I hope to set the stage for the 10 or so talks and posters that will present astrophysical results that have grown out of surveys.
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
Another view
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
High res imaging for measuring physical parameters of the nebulae and their central stars

6. “Modern” SMC Surveys *Magellanic Cloud Emission Line Survey
Survey Team
Number Found
Number New
Depth, mags
SMP 1978 28 3
Jacoby 1980 27 19 5
Sanduleak & Pesch 1981 6
Morgan & Good 1985 13 10
Meyssonnier & Azzopardi 93 62 18 4
Morgan 1995 9
Murphy & Bessel 2000
131
108 ?
Jacoby & De Marco 2002 59 25
Galle, Winkler, & Smith* 69 4?
Jacoby & De Marco 15 7
*Magellanic Cloud Emission Line Survey

7. Technology Helps
The Clouds are easy targets with large format CCD mosaic cameras on large telescopes
Murphy and Bessel 2000
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 Survey Team
Number Found
Number New
Depth, mags
SMP 1978 28 3
Jacoby 1980 27 19 5
Sanduleak 1984 25 13
Morgan & Good 1992 98 86
Morgan 1994
265 54
Leisy, Francois, & Fouqué 10 4 9
Jacoby & De Marco 15 7
Reid & Parker
~1000*
136 7?
*Candidates to be verified

10. “Modern” LMC Surveys *Candidates to be verified Survey Team
The pioneering surveys by Henize (1956), Lindsay (1961), Henize & Westerlund (1963), Lindsay & Mullan (1965), and Westerlund & Smith (1964) defined the extragalactic PN field.
Survey Team
Number Found
Number New
Depth, mags
SMP 1978 28 3
Jacoby 1980 27 19 5
Sanduleak 1984 25 13
Morgan & Good 1992 98 86
Morgan 1994
265 54
Leisy, Francois, & Fouqué 10 4 9
Jacoby & De Marco 15 7
Reid & Parker
~1000*
136 7?
*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
All the new surveys are very productive
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)
LMC will be much better –
Superior statistics
Explore positional dependencies
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
With deeper survey (8 mags)
Currently known, entire LMC 350*
With deeper survey (8 mags)
*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 PN at 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