A kinematic study of the irregular dwarf galaxy NGC 2366 using H I and H alpha observations

Context. The metal content of dwarf galaxies and the metal enrichment of the intergalactic medium both suggest that mass loss from galaxies is a significant factor for the chemical evolution history of galaxies, in particular of dwarf galaxies. However, no clear evidence of a blow-away in local dwarf galaxies has been found so far. Aims. Dwarf galaxies provide a perfect environment for studying feedback processes because their kinematics and their generally low gravitational potential support the long-term survival of shells, filaments, and holes. We therefore performed a detailed kinematic analysis of the neutral and ionised gas in the nearby star-forming irregular dwarf galaxy NGC 2366 in order to make predictions about the fate of the gas and to get a more complete picture of this galaxy. Methods. A deep H alpha image and Fabry-Perot interferometric data of NGC 2366 were obtained. They were complemented by H I synthesis data from the THINGS survey. We searched for line-splitting both in H alpha and H I by performing a Gaussian decomposition. To get an idea whether the expansion velocities are high enough for a gas blow-away, we used the pseudo-isothermal halo model, which gives us realistic values for the escape velocities of NGC 2366. The good data quality also allowed us to discuss some peculiarities of the morphology and the dynamics in NGC 2366. Results. A large red-shifted outflow north west of the giant extragalactic H II region with an expansion velocity of up to 50 km s(-1) is found in H alpha, but not in H I. Additionally, a blue-shifted component north of the giant extragalactic H II region was detected both in H alpha and H I with an expansion velocity of up to 30 km s(-1). A comparison with the escape velocities of NGC 2366 reveals that the gas does not have enough kinetic energy to leave the gravitational potential. Conclusions. This result is in good agreement with hydrodynamic simulations and suggests that we need to examine even less massive galaxies (M(gas) = 10(6) M(circle dot)).