We present deep WIYN H \alpha imaging of the dwarf irregular starburst galaxy NGC 1569 , together with WIYN SparsePak spatially-resolved optical spectroscopy of the galactic outflow .
This leads on from our previous detailed analyses of the state of the ISM in the central regions of this galaxy .
Our deep imaging reveals previously undetected ionized filaments in the outer halo .
Through combining these results with our spectroscopy we have been able to re-define the spatial extent of the previously catalogued superbubbles , and derive estimates for their expansion velocities , which we find to be in the range 50–100 km s ^ { -1 } .
The implied dynamical ages of \lesssim 25 Myr are consistent with the recent star- and cluster-formation histories of the galaxy .
Detailed decomposition of the multi-component H \alpha line has shown that within a distinct region \sim 700 \times 500 pc in size , roughly centred on the bright super star cluster A , the profile is composed of a bright , narrow ( FWHM \lesssim 70 km s ^ { -1 } ) feature with an underlying , broad component ( FWHM \sim 150 km s ^ { -1 } ) .
Applying the conclusions found in our previous work regarding the mechanism through which the broad component is produced , we associate the faint , broad emission with the interaction of the hot , fast-flowing winds from the young star clusters with cool clumps of ISM material .
This interaction generates turbulent mixing layers on the surface of the clouds and the evaporation and/or ablation of material into the outflow .
Under this interpretation , the extent of the broad component region may indicate an important transition point in the outflow , where ordered expansion begins to dominate over turbulent motion .
In this context , we present a multi-wavelength discussion of the evolutionary state of the outflow .