We present evidence of large-scale outflows from three low-mass ( log ( M _ { * } /M _ { \odot } ) \sim 9.75 ) star-forming ( SFR > 4 M _ { \odot } yr ^ { -1 } ) galaxies observed at z = 1.24 , z = 1.35 and z = 1.75 in the 3D-HST Survey .
Each of these galaxies is located within a projected physical distance of 60 kpc around the sight line to the quasar SDSS J123622.93+621526.6 , which exhibits well-separated strong ( W _ { r } ^ { \lambda 2796 } \gtrsim 0.8 Å ) Mg II absorption systems matching precisely to the redshifts of the three galaxies .
We derive the star formation surface densities from the H \alpha emission in the WFC3 G141 grism observations for the galaxies and find that in each case the star formation surface density well-exceeds 0.1 M _ { \odot } yr ^ { -1 } kpc ^ { -2 } , the typical threshold for starburst galaxies in the local Universe .
From a small but complete parallel census of the 0.65 < z < 2.6 galaxies with H _ { 140 } \lesssim 24 proximate to the quasar sight line , we detect Mg II absorption associated with galaxies extending to physical distances of 130 kpc .
We determine that the W _ { r } > 0.8 Å Mg II covering fraction of star-forming galaxies at 1 < z < 2 may be as large as unity on scales extending to at least 60 kpc , providing early constraints on the typical extent of starburst-driven winds around galaxies at this redshift .
Our observations additionally suggest that the azimuthal distribution of W _ { r } > 0.4 Å Mg II absorbing gas around star-forming galaxies may evolve from z \sim 2 to the present , consistent with recent observations of an increasing collimation of star formation-driven outflows with time from z \sim 3 .