We present high velocity resolution ( \sim 1.6 km s ^ { -1 } ) Giant Meterwave Radio Telescope ( GMRT ) HI 21 cm synthesis images of the dwarf galaxies KK98 250 and KK98 251 , as well as optical broad band images of KK98 250 .
We find that , despite being faint ( { M _ { B } } \lesssim - 14 ) , both galaxies have regular velocity fields .
In both cases the velocity fields are consistent with rigid body rotation .
We derive rotation curves for the galaxies and fit mass models to them .
For both galaxies , we find acceptable fits using isothermal halos while NFW halos provide a poor fit .
Finally , we compile from literature a sample of galaxies with HI synthesis observations and I band magnitudes .
From this sample we find , in agreement with earlier studies ( which used single dish HI data ) , that dwarf galaxies tend to lie below the I band Tully-Fisher relation defined by brighter galaxies .