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The Survey of HI in Extremely Low-mass Dwarfs (SHIELD) is an on-goingmulti-wavelength program to characterize the gas, star formation, and evolutionin gas-rich, very low-mass galaxies that populate the faint end of the galaxyluminosity function. The galaxies were selected from the first ~10% of the HIALFALFA survey based on their low HI mass and low baryonic mass. Here, wemeasure the star-formation properties from optically resolved stellarpopulations for 12 galaxies using a color-magnitude diagram fitting technique.We derive lifetime average star-formation rates (SFRs), recent SFRs, stellarmasses, and gas fractions. Overall, the recent SFRs are comparable to thelifetime SFRs with mean birthrate parameter of 1.4, with a surprisingly narrowstandard deviation of 0.7. Two galaxies are classified as dwarf transitiongalaxies (dTrans). These dTrans systems have star-formation and gas propertiesconsistent with the rest of the sample, in agreement with previous results thatsome dTrans galaxies may simply be low-luminosity dIrrs. We do not find acorrelation between the recent star-formation activity and the distance to thenearest neighboring galaxy, suggesting that the star-formation process is notdriven by gravitational interactions, but regulated internally. Further, wefind a broadening in the star-formation and gas properties (i.e., specificSFRs, stellar masses, and gas fractions) compared to the generally tightcorrelation found in more massive galaxies. Overall, the star-formation and gasproperties indicate these very low-mass galaxies host a fluctuating,non-deterministic, and inefficient star-formation process.

Characterizing the Star Formation of the Low-Mass SHIELD Galaxies from Hubble Space Telescope Imaging