IMAGING SPECTROPHOTOMETRY OF THE ORION NEBULA CORE .1. EMISSION-LINE MAPPING AND PHYSICAL CONDITIONS

The results of a Fabry-Perot imaging spectrophotometric study of the core of the Orion Nebula H II region are presented. Halpha Hbeta, [O III] lambda5007, [N II] lambdalambda6548, 6583, [S II] lambdalambda6716, 6731, and He I lambda6678 emission-line flux maps have been derived from low-resolution (5 angstrom FWHM) Fabry-Perot CCD interferograms of the inner 6' surrounding the exciting star theta1C Ori. From these fluxes were derived maps of the principal emission-line diagnostic ratios of [N II] lambda6583/Halpha, [O III] lambda5007/Hbeta, [S II] lambdAlambda6716+31/Halpha, Halpha/Hbeta, [S II] lambda6716/lambda6731, and He I lambda6678/Halpha, and these are used to trace in detail the run of excitation, extinction, electron density, and ionic abundances across the face of the nebula at a spatial resolution of 2". Using two methods we find a helium ionic abundance of He+/H+ = 0.088 +/- 0.008, consistent with previous single-point spectroscopic determinations.