We present chemical abundances and velocities of five stars between 0.3 and 1.1kpc from the center of the TucanaII ultrafaint dwarf galaxy (UFD) from high-resolution Magellan/MIKE spectroscopy. We find that every star is deficient in metals (-3.6<[Fe/H]<-1.9) and in neutron-capture elements as is characteristic of UFD stars, unambiguously confirming their association with TucanaII. Other chemical abundances (e.g., C, iron peak) largely follow UFD trends and suggest that faint core-collapse supernovae (SNe) dominated the early evolution of TucanaII. We see a downturn in [{alpha}/Fe] at [Fe/H]~-2.8, indicating the onset of Type Ia SN enrichment and somewhat extended chemical evolution. The most metal-rich star has strikingly low [Sc/Fe]=-1.29{+/-}0.48 and [Mn/Fe]=-1.33{+/-}0.33, implying significant enrichment by a sub-Chandrasekhar mass Type Ia SN. We do not detect a radial velocity gradient in TucanaII (dv_helio_/d{theta}1=-2.6_-2.9_^+3.0^km/s/kpc), reflecting a lack of evidence for tidal disruption, and derive a dynamical mass of M_1/2_(r_h_)=1.6_-0.7_^+1.1^x10^6^M{sun}. We revisit formation scenarios of the extended component of TucanaII in light of its stellar chemical abundances. We find no evidence that TucanaII had abnormally energetic SNe, suggesting that if SNe drove in situ stellar halo formation, then other UFDs should show similar such features. Although not a unique explanation, the decline in [{alpha}/Fe] is consistent with an early galactic merger triggering later star formation. Future observations may disentangle such formation channels of UFD outskirts.

Cone search capability for table J/AJ/165/55/stars (Parameters for observed stars (paste table1 and table2))

Cone search capability for table J/AJ/165/55/table6 (*Velocity measurements)