A kinematical study of the dwarf irregular galaxy NGC 1569 and its supernova remnants

Abstract

ABSTRACT We present Fabry-Pérot observations in the H α and [S ii] lines to study the kinematics of the Magellanic-type dwarf irregular galaxy NGC 1569, these observations allowed us to compute the H α velocity field of this galaxy. Doing a detailed analysis of the velocity along the line of sight and H α velocity profiles, we identified the origin of most of the motions in the innermost parts of the galaxy and discarded the possibility of deriving a rotation curve that traces the gravitational well of the galaxy. We analysed the kinematics of the ionized gas around 31 supernova remnants previously detected in NGC 1569 by other authors, in optical and radio emission. We found that the H α velocity profiles of the supernova remnants are complex indicating the presence of shocks. Fitting these profiles with several Gaussian functions, we computed their expansion velocities which rank from 87 to 188 km s−1 confirming they are supernova remnants. Also, we determined the physical properties such as electron density, mechanical energy, and kinematic age for 30 of the 31 supernova remnants and found they are in the radiative phase with an energy range from 1 to 39 × 1050 erg s−1 and an age from 2.3 to 8.9 × 104 yr. Finally, we estimated the Surface Brightness–Diameter (Σ–D) relation for NGC 1569 and obtained a slope β = 1.26 ± 0.2, comparable with the β value obtained for supernova remnants in galaxies M31 and M33.