A catalog of planetary nebula candidates and HII regions in NGC 3109*
Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70264, Méx. D.F., 04510 México e-mail: email@example.com
2 Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 877, Ensenada, B.C., México e-mail: firstname.lastname@example.org
3 LUTH, Observatoire de Meudon, Meudon Cedex, France e-mail: email@example.com
Accepted: 30 December 2006
Aims.Images obtained with the ESO VLT and FORS1 in [O iii] 5007 on- and off-band, as well as r_Gunn filters, are analyzed to search for planetary nebula (PN) candidates.
Methods.In the continuum-subtracted [O iii] 5007 on-band images, a large number of emission-line regions were detected. We describe the criteria employed for distinguishing PN candidates from compact HII regions.
Results. The most unambiguous discriminators for the two classes of nebulae are the sizes and properties of the ionizing stars. Based upon these criteria, we have found 20 PN candidates for which we present coordinates, nebular [O iii] fluxes, and stellar magnitudes. The cumulative luminosity function for these PNe is discussed. A catalog of HII regions listing coordinates, nebular [O iii] fluxes, stellar magnitudes, and other characteristics is also presented. We find that HII regions are rather concentrated towards the disk of the galaxy, while PNe are distributed also above and below this structure, consistent with their belonging to an older stellar population.
Key words: galaxies: individual: NGC 3109 (DDO 236) / ISM: planetary nebulae: general / ISM: HII regions / galaxies: ISM
© ESO, 2007