The H I kinematics and distribution of four blue compact dwarf galaxies

We present VLA H I observations of the blue compact dwarf (BCD) galaxies NGC 2366, NGC 4861, VII Zw 403, and Haro 2. These galaxies span a range of BCD morphological types. The cometary-like BCDs NGC 2366 and NGC 4861 have regular rotational kinematics with a V/sigma of 8.7 and 6.4, respectively. On the other hand, the velocity fields of the iE BCD VII Zw 403 and of the nE BCD Haro 2 lack regularity, and their rotational motion is around the major, not the minor, axis. The H I distribution is centrally peaked in VII Zw 403 and Haro 2, a general feature of all iE and nE- type BCDs, the most common ones. In contrast, cometary-type BCDs have multiple H I peaks that are scattered over the disk. The active regions of star formation are associated with regions of high H I column densities, with slight displacements between the H I and stellar peaks. NGC 2366 shows many H I minima, resulting from the disruptive influence of massive star formation and supernovae on the interstellar medium ( ISM). In NGC 2366 and NGC 4861, there is a tendency for H I gas with a higher velocity dispersion to be associated with regions of lower H I column density. This anticorrelation can be understood in the context of a two-phase model of the ISM. In all BCDs, the radio continuum emission is associated with the star-forming regions and is predominantly thermal in nature. H I clouds with no optical counterparts have been found in the vicinity of NGC 4861 and Haro 2.