An improved method for statistical studies of the internal kinematics of H ii regions: the case of M83

Abstract

We present the integrated Hα emission line profile for 157 H <scp>ii</scp> regions in the central 3.4 × 3.4 arcmin2 of the galaxy M83 (NGC 5236). Using the Fabry–Perot interferometer GHαF<scp>a</scp>S, on the 4.2-m William Herschel Telescope on La Palma, we show the importance of a good characterization of the instrumental response function for the study of line profile shapes. The luminosity–velocity dispersion relation is also studied, and in the log(<it>L</it>)–log(σ) plane we do not find a linear relation, but an upper envelope with equation log(<it>L</it><inf>Hα</inf>) = 0.9 log(σ) + 38.1. For the adopted distance of 4.5 Mpc, the upper envelope appears at the luminosity <it>L</it>= 1038.5 erg s−1, in full agreement with previous studies of other galaxies, reinforcing the idea of using H <scp>ii</scp> regions as standard candles.