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We report the first sub-kiloparsec spatial resolution measurements ofstrongly inverted gas-phase metallicity gradients in two dwarf galaxies at$z$$\sim$2. The galaxies have stellar masses $\sim$$10^9M_\odot$, specificstar-formation rate $\sim$20 Gyr$^{-1}$, and global metallicity $12+\log({\rmO/H})\sim8.1$ (1/4 solar), assuming the Maiolino et al. (2008) strong linecalibrations of OIII/Hb and OII/Hb. Their metallicity radial gradients aremeasured to be highly inverted, i.e., 0.122$\pm$0.008 and 0.111$\pm$0.017dex/kpc, which is hitherto unseen at such small masses in similar redshiftranges. From the Hubble Space Telescope observations of the source nebularemission and stellar continuum, we present the 2-dimensional spatial maps ofstar-formation rate surface density, stellar population age, and gas fraction,which show that our galaxies are currently undergoing rapid mass assembly viadisk inside-out growth. More importantly, using a simple chemical evolutionmodel, we find that the gas fractions for different metallicity regions cannotbe explained by pure gas accretion. Our spatially resolved analysis based on amore advanced gas regulator model results in a spatial map of net gaseousoutflows, triggered by active central starbursts, that potentially play asignificant role in shaping the spatial distribution of metallicity byeffectively transporting stellar nucleosynthesis yields outwards. The relationbetween wind mass loading factors and stellar surface densities measured indifferent regions of our galaxies shows that a single type of wind mechanism,driven by either energy or momentum conservation, cannot explain the entiregalaxy. These sources present a unique constraint on the effects of gas flowson the early phase of disk growth from the perspective of spatially resolvedchemical evolution within individual systems.

Discovery of Strongly Inverted Metallicity Gradients in Dwarf Galaxies at $z$$\sim$2