A new planetary nebula in the outer reaches of the Galaxy

¹ Instituto de Astrofísica de Canarias (IAC), C/Vía Láctea s/n, 38200 La Laguna, Tenerife Spain
² Centro Astronómico Hispano Alemán, Calar Alto, C/Jesús Durbán Remón 2-2, 04004 Almeria, Spain
³ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), C/General Pizarro 1-1, 44001 Teruel, Spain
e-mail: kerttu@cefca.es
⁴ Departamento de Astrofísica, Universidad de La Laguna, Av. Astrofísico Francisco Sánchez, s/n, 38206 La Laguna, Spain
⁵ Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
⁶ Department of Physics and Astronomy, Macquarie University, North Ryde, NSW 2109, Australia
⁷ Institut für Physik, Karl-Franzens Universität Graz, Universitätsplatz 5, 8010 Graz, Austria
⁸ Nordic Optical Telescope, Ap. 474, 38700, S/C de La Palma, S/C de Tenerife, Spain
⁹ Tartu Observatory, Tõravere 61602, Estonia
¹⁰ Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen, Denmark
¹¹ Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), Apdo Postal 51 y 216, 72000 Puebla, Mexico
¹² Instituto de Astronomía UNAM, Km. 103 Carretera Tijuana-Ensenada, CP 22860 Ensenada, Baja California, Mexico
¹³ Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ, UK
¹⁴ Departamento de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Ave. Gran Bretaña 1111, Playa Ancha, Casilla 53, Valparaíso, Chile
¹⁵ Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Casilla 306, Santiago 22, Chile
¹⁶ Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
¹⁷ Jodrell Bank Centre for Astrophysics, Alan Turing Building, University of Manchester, Manchester M13 9PL, UK

Received: 30 April 2010
Accepted: 19 April 2011

Abstract

Aims. A proper determination of the abundance gradient in the Milky Way requires the observation of objects at large galactiocentric distances. With this aim, we are exploring the planetary nebula population towards the Galactic anticentre. In this article, the discovery and physico-chemical study of a new planetary nebula towards the anticentre direction, IPHASX J052531.19+281945.1 (PNG 178.1-04.0), is presented.

Methods. The planetary nebula was discovered from the IPHAS survey. Long-slit follow-up spectroscopy was carried out to confirm its planetary nebula nature and to calculate its physical and chemical characteristics.

Results. The newly discovered planetary nebula turned out to be located at a very large galactocentric distance (D_GC = 20.8 ± 3.8 kpc), larger than any previously known planetary nebula with measured abundances. Its relatively high oxygen abundance (12+log(O/H) = 8.36  ±  0.03) supports a flattening of the Galactic abundance gradient at large galactocentric distances rather than a linearly decreasing gradient.