Long-slit spectrophotometry of the H II regions Gum 38a and Gum 38b

Abstract

We present new long-slit spectrophotometric observations in the range 3700-7200 Å of the H II regions Gum 38a and Gum 38b (RCW 57). We study the spatial distribution of reddenig ad excitation throughout the complex by means of emission-line intensities. From the strong re de mg dtfference, we confirm that Gum 38a and Gum 38b are two individual complexes, the former bemg m the foreground. We derive chemical abundances in both nebulae, the results of which are similar to those of the Orion Nebula. This is consistent with the fact that the three nebulae are located at similar Galactocentric d s­ tances. We also discuss the general ionization structure of the complexes based on the spectral propertles of several filaments and diffuse emission around the central bright knots of Gum 38a and beyond. In particular, we found an interesting filament with strong [O I] λλ6300, 6364 lines.