A kinematic study of the irregular dwarf galaxy NGC 4861 using HI and
  Halpha observations
  Context. Outflows powered by the injection of kinetic energy from massive
stars can strongly affect the chemical evolution of galaxies, in particular of
dwarf galaxies, as their lower gravitational potentials enhance the chance of a
galactic wind.
  Aims. We therefore performed a detailed kinematic analysis of the neutral and
ionised gas components in the nearby star-forming irregular dwarf galaxy NGC
4861. Similar to a recently published study of NGC 2366, we want to make
predictions about the fate of the gas and to discuss some general issues about
this galaxy.
  Methods. Fabry-Perot interferometric data centred on the Halpha line were
obtained with the 1.93m telescope at the Observatoire de Haute-Provence. They
were complemented by HI synthesis data from the VLA. We performed a Gaussian
decomposition of both the Halpha and the HI emission lines in order to search
for multiple components indicating outflowing gas. The expansion velocities of
the detected outflows were compared to the escape velocity of NGC 4861, which
was modelled with a pseudo-isothermal halo.
  Results. Both in Halpha and HI the galaxy shows several outflows, three
directly connected to the disc and probably forming the edges of a supergiant
shell, and one at kpc-distance from the disc. We measured velocity offsets of
20 to 30 km/s, which are low in comparison to the escape velocity of the galaxy
and therefore minimise the chance of a galactic wind.
