EDP Sciences
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Volume 407, Number 1, August III 2003
Page(s) 51 - 59
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20030732

A&A 407, 51-59 (2003)
DOI: 10.1051/0004-6361:20030732

The Local Group Census: Planetary nebulae in IC 10 , Leo A and Sextans A

L. Magrini1, R. L. M. Corradi2, R. Greimel2, P. Leisy2, 3, D. J. Lennon2, A. Mampaso3, M. Perinotto1, D. L. Pollacco4, J. R. Walsh5, N. A. Walton6 and A. A. Zijlstra7

1  Dipartimento di Astronomia e Scienza dello Spazio, Universitá di Firenze, L.go E. Fermi 2, 50125 Firenze, Italy
2  Isaac Newton Group of Telescopes, Apartado de Correos 321, 38700 Santa Cruz de La Palma, Canarias, Spain
3  Instituto de Astrofísica de Canarias, c. vía Láctea s/n, 38200, La Laguna, Tenerife, Canarias, Spain
4  School of Pure and Applied Physics, Queen's University Belfast, Belfast BT7 9NN, Northern Ireland, UK
5  ST-ECF, ESO, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
6  Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
7  Physics Department, UMIST, PO Box 88, Manchester M60 1QD, UK

(Received 28 March 2003 / Accepted 6 May 2003 )

In the framework of our narrow-band survey of the Local Group galaxies, we present the results of the search for planetary nebulae (PNe) in the dwarf irregular galaxies IC 10 , Leo A and Sextans A . Using the standard on-band/off-band technique, sixteen new candidate PNe have been discovered in the closest starburst galaxy, IC 10 . The optical size of this galaxy is estimated to be much larger than previously thought, considering the location of the new PNe in an area of 3.6 kpc $\times$ 2.7 kpc. We also confirm the results of previous studies for the other two dwarf irregular galaxies, with the detection of one candidate PN in Leo A and another one in Sextans A . We review the number of planetary nebulae discovered in the Local Group to date and their behaviour with metallicity. We suggest a possible fall in the observed number of PNe when [Fe/H] $\ll$ -1.0, which might indicate that below this point the formation rate of PNe is much lower than for stellar populations of near Solar abundances. We also find non-negligible metallicity effects on the [O III] luminosity of the brightest PN of a galaxy.

Key words: planetary nebulae: general -- galaxies: individual: Leo A, Sextans A, IC 10

Offprint request: R. Corradi, rcorradi@ing.iac.es

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