The distance to NGC 6302

Abstract

New 6 cm continuum and radio recombination line VLA observations as well as CO observations are presented of the bright PN NGC 6302. The H110-alpha line is significantly broader than the H76-alpha line, an effect which is attributed to electron pressure broadening. An electron density of 25,000/cu cm is derived, a value in good agreement with previous optical estimates. Adopting this value and a geometric model for the nebula, a distance of 2.2 + or - 1.1 kpc is derived. An attempt is made to measure the angular expansion in the nebula using 6 cm continuum observations and the technique of Masson (1986). The failure to measure any expansion implies a lower limit of 0.7 + or - 0.3 kpc for the distance. An IRAS luminosity of 13,000 solar, an ionized nebular mass of about 0.2 solar, a neutral hydrogen mass of about 0.05 solar, and a molecular hydrogen mass of about 0.5 solar are derived. The luminosity and total mass are among the largest known for PNs.