VLA HI line observations of the extremely metal-poor blue compact dwarf galaxy SBS 0335-052

We present the results of H I mapping with the NRAO(2) VLA of one of the mo st metal-deficient blue compact dwarf (BCD) galaxies known, SBS 0335-052, w ith an oxygen abundance only 1/40 that of the Sun. We study the structure a nd dynamics of the neutral gas in this chemically young object with a spati al resolution of 20.5" x 15" (similar to5.4 x 3.9 kpc at an assumed distanc e of 54.3 Mpc), a sensitivity at the 2 sigma detection level of similar to2 .0 K or 7.5 x 10(19) cm(-2) and a velocity resolution of 21.2 km s(-1). We detected a large H I complex associated with this object having an overall size of about 66 by 22 kpc and elongated in the east-west direction. There are two prominent, slightly resolved peaks visible in the integrated H I ma p, separated in the east-west direction by 22 kpc (84 "). The eastern peak is nearly coincident with the position of the optical galaxy SBS 0335-052. The western peak is about a factor of 1.3 brighter in the H I line and is i dentified with a faint blue compact dwarf galaxy, SBS 0335-052W, with m(B) = 19.4, and a metallicity close to the lowest values known for BCDs, about 1/50 that of the Sun. The radial velocities of both systems are similar, su ggesting that the two BCDs, SBS 0335-052 and SBS 0335-052W, constitute a pa ir of dwarf galaxies embedded in a common H I envelope. Alternatively, the BCDs may be the nuclei of two distinct interacting primordial H I clouds. T he estimated total dynamical mass, assuming the BCDs form a bound system, i s larger than similar to6 x 10(9) M., compared with a total gaseous mass M- gas = 2.1 x 10(9) m. and a total stellar mass M-star less than or similar t o 10(8) M. Hence, the mass of the SBS 0335-052 system is dominated by dark matter. Because of the disturbed H I velocity field and the presence of wha t might be tidal tails at either end of the system, we favor the hypothesis of tidal triggering of the star formation in this system. It can be due to either the nearby giant galaxy NGC 1376 or the mutual gravitational intera ction of the two H I clouds.