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We present a study of the ultra-faint Milky Way dwarf satellite galaxy TucanaII using deep photometry from the 1.3m SkyMapper telescope at Siding SpringObservatory, Australia. The SkyMapper filter-set contains ametallicity-sensitive intermediate-band $v$ filter covering the prominent Ca IIK feature at 3933.7A. When combined with photometry from the SkyMapper $u, g$,and $i$ filters, we demonstrate that $v$ band photometry can be used to obtainstellar metallicities with a precision of $\sim0.20$dex when [Fe/H] $> -2.5$,and $\sim0.34$dex when [Fe/H] $< -2.5$. Since the $u$ and $v$ filters bracketthe Balmer Jump at 3646A, we also find that the filter-set can be used toderive surface gravities. We thus derive photometric metallicities and surfacegravities for all stars down to a magnitude of $g\sim20$ within $\sim$75arcminutes of Tucana II. Photometric metallicity and surface gravity cutsremove nearly all foreground contamination. By incorporating Gaia propermotions, we derive quantitative membership probabilities which recover allknown members on the red giant branch of Tucana II. Additionally, we identifymultiple likely new members in the center of the system and candidate membersseveral half-light radii from the center of the system. Finally, we present ametallicity distribution function derived from the photometric metallicities oflikely Tucana II members. This result demonstrates the utility of wide-fieldimaging with the SkyMapper filter-set in studying UFDs, and in general, lowsurface brightness populations of metal-poor stars. Upcoming work will clarifythe membership status of several distant stars identified as candidate membersof Tucana II.

Stellar metallicities from SkyMapper photometry I: A study of the Tucana II ultra-faint dwarf galaxy