2005ApJ...630L..25P

Blue compact dwarf galaxies (BCDs) are faint (M_B≤-17 mag), compact (R<1 kpc), and at least qualitatively very blue galaxies, due to active star formation, and have low metallicities. Found serendipitously as part of a redshift survey of faint galaxies with the Keck Telescope (DEEP), SA 68-6597 is at a distance of 80 Mpc, and is one of the faintest (-12.4 mag), lowest metallicity (∼0.05 Z_☉) BCDs known. Its Hβ line width of σ=27 km/s and small size, R_eff∼190 pc, suggest that it is an extremely low mass galaxy. We have used the Arecibo telescope to measure the H I properties of SA 68-6597 in order to better constrain its total mass and its potential for future star formation. SA 68-6597 has a M_HI_=(1.4±0.4)x10⁷ M_☉ and an H I FWHM line width of 33⁺⁶⁰_–12. Combining the H I line width with an estimate of the size of the H I disk, we derive a M_dyn≳3x10⁷ M_☉. The values M_HI_/LB_=1.0±0.3 M_☉/L_☉, M_dyn/L_B≥2 M_☉/L_☉, and M_HI_/Mdyn_≲0.47 are typical for BCDs. Combining the measured star formation rate of 0.003 M_☉/yr with the H I mass, we derive a gas depletion timescale of 5±2 Gyr. While SA 68-6597 is a fainter, lower mass, higher metallicity counterpart to other BCDs like I Zw 18 and SBS 0335-052, its H I properties suggest that it will not evolve dramatically in the near future. Given the limits on its gaseous and dynamical masses, SA 68-6597 may be able to evolve into a moderately massive dwarf spheroidal galaxy.