The Eta Carinae Nebula and Centaurus A Near 1400 Mc/s. II. Physical Discussion of the Eta Carinae Nebula

Abstract

The 1400 Mcls observations of NGC 3372 described in Paper I (Hindman and Wade 1959) are discussed. Comparison of the flux densities at 85· 5 Mcls (Mills, Little, and Sheridan 1956) and at 1400 Mcls leads to a value of 10,000±1000 OK for the electron temperature of the nebula. Unpublished optical measurements of the distribution of surface brightness across the object, made by Gum, indicate that there is a dense core about 24 min of arc in diameter, surrounded by a much less dense region with a diameter of 120 min of arc. Adopting the optically determined distance of 1400 parsecs (Hoffieit 1953), we find r.m.s. densities of 71 ions cm-3 in the core and 11 ions cm-3 in the outer region. The total mass of the object is not more than 25,000 solar masses. It is shown that several O·stars probably are needed to maintain the ionization of the nebula.