Exploring the making of a galactic wind in the star-bursting dwarf
  irregular galaxy IC 10 with LOFAR
  Low-mass galaxies are subject to strong galactic outflows, in which cosmic
rays may play an important role, they can be best traced with low-frequency
radio continuum observations, which are less affected by spectral ageing. We
present a study of the nearby star burst dwarf irregular galaxy IC 10 using
observations at 140 MHz with the LOw-Frequency ARray (LOFAR), at 1580 MHz with
the Very Large Array (VLA) and at 6200 MHz with the VLA and the 100-m
Effelsberg telescope. We find that IC 10 has a low-frequency radio halo, which
manifests itself as a second component (thick disc) in the minor axis profiles
of the non-thermal radio continuum emission at 140 and 1580 MHz. These profiles
are then fitted with 1D cosmic-ray transport models for pure diffusion and
advection. We find that a diffusion model fits best, with a diffusion
coefficient of $D=(0.4$-$0.8) \times 10^{26}(E/{\rm GeV})^{0.5}~{\rm
cm^2\,s^{-1}}$, which is at least an order of magnitude smaller than estimates
both from anisotropic diffusion and the diffusion length. In contrast,
advection models, which cannot be ruled out due to the mild inclination, while
providing poorer fits, result in advection speeds close to the escape velocity
of $\approx$$50~\rm km\,s^{-1}$, as expected for a cosmic-ray driven wind. Our
favoured model with an accelerating wind provides a self-consistent solution,
where the magnetic field is in energy equipartition with both the warm neutral
and warm ionized medium with an important contribution from cosmic rays.
Consequently, cosmic rays can play a vital role for the launching of galactic
winds in the disc--halo interface.
