PFP 1: A Large Planetary Nebula Caught in the First Stages of ISM Interaction

M.J.Pierce, D.J.Frew, Q.A.Parker, J.Köppen

ABSTRACT This paper presents (Halpha + [NII]) imaging and spectroscopy of a previously unknown, highly evolved planetary nebula of low excitation which is in the first stages of an interaction with the interstellar medium (ISM). It was discovered srendipitously from AAO/UKST Halpha Survey images as part of a project to exploit the survey data and has evaded detection by previous surveys due to its very low surface brightness. It is a remarkable hollow-sphere planetary nebula, some 19' across, making it one of the largest examples of its type. We estimate a radius of 1.5 kpc and a distance 0f 550 pc as derived from a new Halpha surface brightness-radius relation. PFP 1 has near perfect spherical symmetry, broken only at the NW edge which is coupled with significantly increased (Halpha + [NII]) intensity, both of which provide evidence for an interaction with the ISM. We find a near solar composition for this object with possibly enhanced He and N abundances. A blue central star candidate has been intedified from the SuperCOSMOS Sky Survey data.