We present WSRT observations of high sensitivity and resolution of the neutral hydrogen in the starburst dwarf galaxy NGC 1569 .
Assuming a distance of 2.2 Mpc , we find a total HI mass of 1.3 \times 10 ^ { 8 } M _ { \odot } to be distributed in the form of a dense , clumpy ridge surrounded by more extended diffuse HI containing a few additional discrete features , such as a Western HI Arm and an HI bridge reaching out to a small counterrotating companion cloud .
About 10 % by mass of all HI in NGC 1569 is at unusually high velocities .
Some of this HI may be associated with the mass outflow evident from H \alpha measurements , but some may also be associated with NGC 1569 ’ s HI companion and intervening HI bridge , in which case , infall rather than outflow might be the cause of the discrepant velocities .
No indication of a large bubble structure was found in position-velocity maps of the high-velocity HI .
The galaxy as a whole is in modest overall rotation , but the HI gas lacks any sign of rotation within 60 ^ { \prime \prime } ( 0.6 kpc ) from the center , i.e .
over most of the optical galaxy .
Here , turbulent motions resulting from the starburst appear to dominate over rotation .
In the outer disk , the rotational velocities reach a maximum of 35 \pm 6 km s ^ { -1 } , but turbulent motion remains significant .
Thus , starburst effects are still noticeable in the outer HI disk , although they are no longer dominant beyond 0.6 kpc .
Even excluding the most extreme high-velocity HI clouds , NGC 1569 still has an unusually high mean HI velocity dispersion of \sigma _ { v } = 21.3 km s ^ { -1 } , more than double that of other dwarf galaxies .