We present 21cm H i line observations of the blue compact dwarf galaxy NGC 1705 .
Previous optical observations show a strong outflow powered by an ongoing starburst dominating the H ii morphology and kinematics .
In contrast , most of the H i lies in a rotating disk .
An extraplanar H i spur accounts for \sim 8 % of the total H i mass , and is possibly associated with the H ii outflow .
The inferred mass loss rate out of the galaxy ’ s core is significant \sim 0.2 - 2 \mbox { $ { \cal M } _ { \odot } $ } { yr ^ { -1 } } , but does not dominate the H i dynamics .
Mass model fits to the rotation curve show that the dark matter ( DM ) halo is dominant at nearly all radii and has a central density \rho _ { 0 } \approx 0.1 \mbox { $ { \cal M } _ { \odot } $ } { pc ^ { -3 } } : ten times higher than typically found in dwarf irregular galaxies , but similar to the only other mass-modelled blue compact dwarf , NGC 2915 .
This large difference strongly indicates that there is little evolution between dwarf irregular and blue compact dwarf types .
Instead , dominant DM halos may regulate the morphology of dwarf galaxies by setting the critical surface density for disk star formation .
Neither our data nor catalogue searches reveal any likely external trigger to the starburst in NGC 1705 .