Carbon in Orion

Abstract

The carbon abundance in the Orion nebula is redetermined from a detailed study of UV spectra in the IUE archives. Temperature and electron density gradients were derived for the inner 5 arcmin of the nebula using new and existing observational data. These temperatures and densities were used to calculate the carbon abundance for 19 positions largely north or west of the Trapezium. The new carbon abundance is found to be log(C/H) + 12 = 7.83 (+0.13, -0.20). This is 0.5-0.7 dex lower than previous studies found. New atomic parameters, a newer UV-extinction curve, and higher temperatures account for these differences from previous studies. C/H and C/O are found to be constant across the face of the nebula. The influence of temperature fluctuations on abundances was investigated.