New young planetary nebulae in IPHAS

¹ Instituto de Astrofísica de Canarias (IAC), C/Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain e-mail: kerttu@iac.es
² Isaac Newton Group of Telescopes, Apartado de Correos 321, 38700 Sta. Cruz de La Palma, Spain
³ Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), Apdo Postal 51 y 216, 72000 Puebla, Pue., Mexico
⁴ Institut für Physik, Karl-Franzens Universität Graz, Universitätsplatz 5, 8010 Graz, Austria
⁵ Jodrell Bank Centre for Astrophysics, Alan Turing Building, University of Manchester, Manchester, M13 9PL, UK
⁶ Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ, UK
⁷ Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
⁸ Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL, Nijmegen, The Netherlands
⁹ Department of Physics, Macquarie University, Sydney, Australia
¹⁰ Columbia Astrophysics Lab., 550 W120th St., 1027 Pupin Hall, MC 5247, Columbia University, New York 10027, USA

Received: 23 December 2008
Accepted: 16 March 2009

Abstract

Aims. We search for very small-diameter galactic planetary nebulae (PNe) representing the earliest phases of PN evolution. The IPHAS catalogue of Hα-emitting stars provides a useful basis for this study since all sources present in this catalogue must be of small angular diameter.

Methods. The PN candidates are selected based on their location in two colour-colour diagrams: IPHAS (r' - Hα) vs. (r' - i'), and 2MASS () vs. (H - K_s). Spectroscopic follow-up was carried out on a sample of candidates to confirm their nature.

Results. We present a total of 83 PN candidates. We were able to obtain spectra or find the classification from the literature for 35 candidates. Five of these objects are likely to be new PNe, including one large bipolar PN discovered serendipitously close to an emission-line star. PN distances deduced from extinction-distance relations based on IPHAS field-star photometry are presented for the first time. These yield distance estimates for our objects in the range 2 kpc and 6 kpc. From the data in hand, we conclude that four of the discovered objects are probably young PNe.