1. The Census of Planetary Nebulae in the Local Group
Romano L.M. Corradi
Isaac Newton Group of Telescopes, La Palma
Laura Magrini
Dip. di Astronomia, Universita’ di Firenze

2. The census of planetary nebulae in the Local Group
Romano L.M. Corradi
Isaac Newton Group of Telescopes, La Palma
Laura Magrini
Dip. di Astronomia, Universita’ di Firenze

3. An overview of the Local Group (LG)
galaxy
type
log LV
D (kpc)
M 31 Sb
10.43
760
Milky Way
Sbc
10.31 -
M 33 Sc
9.51
795
LMC Ir
9.35 50
SMC
8.79 60
M 32 E2
8.55
NGC 205
Sph
8.51
IC 10
8.47
660
NGC 6822
dIr
8.35
500
NGC 185
8.19
IC 1613
8.07
725
NGC 147
7.99
WLM
7.71
925
Sagittarius
dSph
7.47 24
Fornax
7.19
138
Pegasus
6.87
Leo I*
6.71
250
And I
dSph
6.67
810
And II
700
Leo A
dIr
6.55
690
DD210*
6.47
1025
SagDIG
6.23
1300
PegasusII
6.19
830
Pisces
6.11
And V
6.03
And III
760
Leo II
5.99
210
Phoenix
5.87
395
Sculptor 87
Cassiopeia
5.75
Tucana
870
Sextans 86
Carina
5.71
100
Draco
5.39 79
Ursa Min
5.35 63
In green galaxies for which data exist to search for PNe or at least one PN is known.
In red data from our LG survey, the new results of it (still unpublished) I will present later
*data not reduced yet

4. At the outer fringes of the LG…
GR 8
dSph
6.59
2200
NGC 3109
dIr
8.27
1360
Antlia
6.33
1330
Sextans B
7.67
1320
Sextans A
7.63
1450
EGB *
6.31
possible physical association
Beyond the LG, the IC342/Maffei group,
the South Polar (Sculptor) group, the M 81 group…
Is the LG ultimately going to merge into an elliptical galaxy with approximately the luminosity of the Milky Way?
Van den Bergh 2000, “The Galaxies of the Local Group”

5. Imaging searches for PNe in the LG
Baade (1955): 5 PNe in M31
~100 PNe in LMC and SMC (see Westerlund 1968)
In the 70’s, Ford and collaborators detected a large number of PNe in M31 (bulge) and a few ones in its companions
Jacoby & Lesser (1981) found PNe in 5 galaxies of the LG
Ciardullo et al. (1989): 429 PNe in M31
Magrini et al. (2000): 134 PNe in M33
Jacoby & De Marco (2002): deep survey of SMC
Merrett et al. (2003): 2611 PNe in M31 with the P.N.S.
the “Local Group Census” ( ): 14 galaxies searched

6. The Local Group Census (LGC)
It is a narrow- and broad-band imaging survey of the galaxies of the LG observable from La Palma (Dec>-30).
Collaborators: J. Beckman, M. Bryce, A. Cardwell, R. Corradi, P. Crowther, R. Greimel, A. Herrero, M. Irwin, P. Leisy, D. Lennon, A. Mampaso, L. Magrini, M. Perinotto, R. Peletier, D. Pollacco, S. Prins, I. Skillen, S. Smartt, L. Smith, J. Telting, E. Tolstoy, J. Walsh, N. Walton, A. Zijlstra, A. Zurita
Institutions: ING, IAC, Open Univ., Univ. of Amsterdam, ESO, Univ. of Firenze, Univ. de Granada, Institute of Astronomy Cambridge, Jodrell Bank, Univ. of Manchester, Queens Univ. Belfast, Univ. College London, Univ. of Nottingham, Univ. of Oxford, Univ. of Victoria, UMIST
It is aimed to find, catalogue and study old and young emission-line populations (e.g. HII regions, planetary nebulae, SN remnants, LBVs, WR stars, symbiotic binaries, etc.) to unprecedented levels.
The value of narrowband images is enhanced with complementary broadband data. This enable the linkages between stellar populations (e.g. AGB  PNe) in the range of LG galaxies to be probed.

7. The LGC observations
Instrumentation: Wide Field Camera of the 2.5m Isaac Newton Telescope (mosaic of four 4k2k CCDs, f.o.v. 3434 arcmin2).
Filters and exposure times: [OIII] (500.8/8 nm), Ha+[NII] (656.8/10), [SII] (672.5/8), HeII (468.6/10) min (24.5 mag) Stromgren Y min Sloan g, r, i min (25,24.5,24)
PNe search methods:
visual search of point-like sources in the [OIII] and Ha+[NII] continuum-subtracted images
[OIII]-g vs. Ha-r color-color diagrams
No constraints on the [OIII]/Ha ratio to (statistically) distinguish from HII regions, because otherwise PNe could be missed and we do not want this, specially in dwarf galaxies where the Pne population size is extremely small

8. [OIII]-g vs. Ha-r color-color diagrams
NGC 205
[OIII]-g
Ha-r

9. Datasets are mostly reduced and public
The LGC observations
The observations have basically being completed during a total of some 40 clear nights (out of 50 allocated). Details can be found at
Datasets are mostly reduced and public

10. poster by Zijlstra & Gesicki
PNe in the Milky Way subgroup
3 PNe
Zijlstra & Walsh 1996 A&A 312 L21
poster by Zijlstra & Gesicki
1 PN
Danziger et al ApJ 220, 458
talk of G. Jacoby
Esposizioni tipiche: 1 ora nei filtri in banda stretta, 20 minuti negli altri

11. Corradi et al. 2004 A&A in prep
PNe in the M31/M33 subgroup
Jacoby & Lesser 1981 AJ
Corradi et al A&A in prep
Ciardullo et al ApJ
Magrini et al A&A

12. M 31 1284 PNe (717 new) in 3.6 deg2 ~2700 PNe talk of H. Merrett
Halliday et al IAU Symp 219 p.629
1284 PNe (717 new) in 3.6 deg2
~2700 PNe talk of H. Merrett

13. IC 10
16 PNe
Magrini et al A&A

14. huge HI envelope 12 x 15 kpc (Huchtmeier 1979 A&A 75 170)
Magrini et al A&A
1.3 x 1.1 kpc
2.5 kpc
Similar result for NGC 6822 (see Leisy talk)
huge HI envelope 12 x 15 kpc
(Huchtmeier 1979 A&A )

15. PNe in “free-floating” galaxies of the LG
NGC PNe talk of P. Leisy
WLM PN Magrini et al MNRAS in prep
IC PNe ” “ “
Leo A PN Jacoby & Lesser 1981 AJ
Magrini et al A&A

16. NGC 6822

17. WLM

18. IC 1613

19. Leo A
The galaxy with the lowest luminosity and metallicity where a PN has been found

20. PNe at the outer fringes of the LG
Sextans B PNe Magrini et al A&A
talk of L. Magrini
Sextans A PN Magrini et al A&A
talk of L. Magrini
NGC PNe Prada et al in preparation
GR PN Magrini et al MNRAS in prep

21. Summary: n. of PNe in the Local Group galaxies
Galaxy
log LV
n.PNe
magc
O/H
M 31
10.43
~2700
9.0
Milky Way
10.31
~2000
8.7
M 33
9.51
134
2.6
8.4
LMC
9.35
277
8.35
SMC
8.79
105 6
8.03
M 32
8.55 30
2.4
8.29
NGC 205
8.51 35
3.5
8.6
IC 10
8.47 16
2.0
8.2
NGC 6822 20
8.25
NGC 185
8.19 5
2.7
7.9
IC 1613
8.07 3
7.71
NGC 147
7.99 9
<4.4
WLM 1
7.78
Sagittarius
7.47
Fornax
7.19
7.98
Pegasus
6.87
7.93
Leo A
6.55
3.0
7.36
Galaxy
log LV
n.PNe
magc
O/H
NGC 3109
8.27 18
7.63
Sextans B
7.67 5
3.0
8.12
Sextans A 1
1.9
7.55
Wide range of luminosities (masses) and metallicities. Excellent resource to study properties of PNe in widely different environments. Completeness limit has been computed correcting for extinction and metallicity the cutoff magnitude

22. Observed population size vs. galaxian luminosity
Milky Way
M 33
LMC
SMC
Leo A
Sagittarius
Pegasus
Fornax
SexA
SexB
N147
I1613
N185
N3109
N6822
I10
N205
M32

23. PNe as tracers of intermediate-age populations
log (mass of intermediate-age stars)N(PNe)
Relative SFR 2-8 Gyrs  0.2
Relative SFR 2-8 Gyrs < 0.2
Mateo 1998 ARAA 36, 435
Magrini et al. in prep.
log (total mass)  van den Bergh 2000

24. Age effects? Same luminosity, morphology, and metallicity
NGC 185 gas-rich and <1Gyr star-formation in its centre
NGC 147 gas-free, no SF in the last 3 Gyrs
NGC185
NGC147
Mendez & Soffner 1997 A&A 321, (mild age effect on M*)
Marigo et al A&A in press (strong effect for recent star formation)
see talk of P. Marigo

25. significant SF <1 Gyr
NGC 185
Martinez-Delgado et al AJ
significant SF <1 Gyr
some SF 1-3 Gyr
very little SF 1-3 Gyr

26. significant SF <1 Gyr
NGC 185
Corradi et al A&A in prep.
significant SF <1 Gyr
SF burst <0.15 Gyr

27. Metallicity effects: the brightest PN
metallicity correction
Dopita et al 1992 AJ
But mixed with population size effects!

28. Summary
PNe have been searched (found) in all LG galaxies with logLV>6.7
Their population size correlates well with the V luminosity of the galaxy, and in particular traces differences in the relative contribution of intermediate-age populations (2-8 Gyr). Deeper searches are needed to strenghten this result
LG PNe are valuable indicators of:
metallicity (see talks/posters Richer, Magrini, Leisy, Stasinska, Perinotto, Kniazev, Maciel)
kinematics (see talk of Merrett for M31, Durrell et al AAS for M33)
intergalactic light (IC 10, NGC 6822)
The effect of star formation in the last 1-2 Gyr on the absolute magnitude of the bright cutoff of the PN luminosity function remains controversial. Possible positive evidence (e.g. NGC 185 vs. NGC 147) is weakened by the small PN population size in most LG galaxies