Study of Extragalactic H <scp>ii</scp> Regions with Échelle Spectroscopy: The A2 Region in the Irregular Galaxy IC 4662

Abstract I present the results of échelle spectroscopy of a bright H ii region in the irregular galaxy IC 4662 and their comparison with results from long-slit spectroscopy of the same region. All observations were obtained with the standard spectrographs of the Southern African Large Telescope: (1) low and medium spectral resolution spectrograph Robert Stobie Spectrograph ( R ≈ 800) and (2) échelle spectrograph HRS ( R = 16,000–1,7000). In both types of data the intensities of most of the emission lines were measured and abundances of oxygen and N, Ne, S, Ar, Cl and Fe were determined as well as physical parameters of the H ii region. The chemical abundances were obtained from both types of data with the T e -method. Abundances calculated from both types of data agree to within the cited uncertainties. The analysis of the échelle data revealed three distinct kinematic subsystems within the studied H ii region: a narrow component (NC, σ ≈ 12 km s −1 ), a broad component (BC, σ ≈ 40 km s −1 ), and a very broad component (VBC, σ ≈ 60–110 km s −1 , detected only in the brightest emission lines). The elemental abundances for the NC and BC subsystems were determined using the T e -method. The velocity dispersion dependence on the ionization potential of elements showed no correlation for the NC, indicating a well-mixed turbulent medium, while the BC exhibited pronounced stratification, characteristic of an expanding shell. Based on a detailed analysis of the kinematics and chemical composition, it was concluded that the BC is associated with the region surrounding a Wolf-Rayet (WR) star of spectral type WN7-8. The stellar wind from this WR star interacts with a shell ejected during an earlier evolutionary stage (either as a red supergiant or a luminous blue variable, LBV), which is enriched in nitrogen. These findings highlight the importance of high spectral resolution for detecting small-scale (∼25 pc) chemical inhomogeneities and for understanding the feedback mechanisms of massive stars in low-metallicity environments.