Detection and study of the compact HII region N26A-B in the Small Magellanic Cloud

Abstract

This paper presents new imagery and spectrophotometric results for the N26 HII region in the Small Magellanic Cloud. The observations using monochromatic images and low-resolution spectra (3700-10 000 Å) reveal a compact and complex nebula composed of two cores A and B where A in the region of Hβ is brighter than B by a factor ~5 and distance of 2″. The core A of 1 or 0.6 pc presents a high excitation [O III] Hβ up to ~8 and a high reddening , while the core B is less excited but has a higher reddening ≥0.8. Each core contains one exciting source; the brighter one should be responsible for the high excitation of A. The apparent spectral type of the two cores ranges from O7 to O9 V and the gas electron density and temperature were derived from the absorption and emission-line intensities. The total mass of the ionized gas is evaluated at 13 . The chemical abundances of He, O, N, Ne, S, and Ar were computed. These abundances seem consistent with average abundances for SMC HII regions, except N that appears slightly overabundant. N26A-B is comparable to the objects previously observed in the LMC and SMC that we have called "blobs".