The Census of Planetary Nebulae in the Local Group

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) *data not reduced yet

4. possible physical association At the outer fringes of the LG… 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” (2001-2004): 14 galaxies searched

6. The Local Group Census (LGC) It is anarrow- 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

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34arcmin2). Filters and exposure times: [OIII] (500.8/8 nm), Ha+[NII] (656.8/10), [SII] (672.5/8), HeII (468.6/10) 60 min (24.5 mag) Stromgren Y 30 min Sloan g, r, i 20 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

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

9. 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 http://www.ing.iac.es/~rcorradi/LGC Datasets are mostly reduced and public

10. 3 PNe Zijlstra & Walsh 1996 A&A 312 L21 poster by Zijlstra & Gesicki 1 PN Danziger et al. 1978 ApJ 220, 458 talk of G. Jacoby PNe in the Milky Way subgroup

11. Jacoby & Lesser 1981 AJ 86 185 Magrini et al. 2000 A&A 355 713 Corradi et al. 2004 A&A in prep Ciardullo et al. 1989 ApJ 339 53 PNe in the M31/M33 subgroup

12. M 31 Halliday et al. 2003 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. 2003 A&A 407 51

14. Magrini et al. 2003 A&A 407 51 1.3 x 1.1 kpc 2.5 kpc huge HI envelope 12 x 15 kpc (Huchtmeier 1979 A&A 75 170)

15. PNe in “free-floating” galaxies of the LG NGC 6822 20 PNe talk of P. Leisy WLM 1 PNMagrini et al. 2004 MNRAS in prep IC 1613 3 PNe ” “ “ Leo A 1 PNJacoby & Lesser 1981 AJ 86 185 Magrini et al. 2003 A&A 407 51

16. NGC 6822

17. WLM

18. IC 1613

19. Leo A

20. PNe at the outer fringes of the LG Sextans B 5 PNeMagrini et al. 2002 A&A 386 869 talk of L. Magrini Sextans A 1 PNMagrini et al. 2003 A&A 407 51 talk of L. Magrini NGC 3109 18 PNePrada et al. 2004 in preparation GR 8 0 PNMagrini et al. 2004 MNRAS in prep

21. Summary: n. of PNe in the Local Group galaxies

22. M 31 Milky Way LMC M 33 SMC M32 I10 N205 N3109 N6822 SexB N185 Sagittarius N147 Leo A SexA I1613 Fornax Pegasus Observed population size vs. galaxian luminosity

23. Mateo 1998 ARAA 36, 435 Relative SFR 2-8 Gyrs  0.2 Relative SFR 2-8 Gyrs < 0.2 log (mass of intermediate-age stars)N(PNe) PNe as tracers of intermediate-age populations 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, 898 (mild age effect on M*) Marigo et al. 2004 A&A in press (strong effect for recent star formation) see talk of P. Marigo

25. significant SF <1 Gyr some SF 1-3 Gyr very little SF 1-3 Gyr Martinez-Delgado et al. 1999 AJ 118 2229 NGC 185

26. NGC 185 Corradi et al. 2004 A&A in prep. significant SF <1 Gyr SF burst <0.15 Gyr

27. metallicity correction Dopita et al 1992 AJ 389 27 Metallicity effects: the brightest PN 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 (seetalks/posters Richer, Magrini, Leisy, Stasinska, Perinotto, Kniazev, Maciel) • kinematics (seetalk of Merrettfor M31, Durrell et al. 2002 AAS 201 1311 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