Orion Nebula - High resolution Pa-12 mapping

A detailed map of the Paschen-12 (8750 A) line intensity across the central regions of the Orion Nebula is presented which was derived from observations with a tilting-filter Fabry-Perot interferometer mounted at the Cassegrain focus of a 182-cm telescope. The Pa-12 fluxes are compared with an H-alpha photograph and detailed H-alpha intensity tracings of the same regions in order to determine the variation of absorption in the different areas. Using recombination-line theory, it is found that the H-alpha absorption exceeds that in Pa-12 by 0.60 (plus or minus 0.20) magnitude over most of the visible nebula. The mottled appearance of the nebula is attributed to density variations of the gas inside the H II region and to nonuniformities in the dust distribution. Normalized column densities of the absorbing dust toward the Trapezium are plotted as a contour map, and interesting features in other areas are noted. It is concluded that the reddening law for starlight and nebular emission is the same.