Large-Scale Star Formation-Driven Outflows at 1<z<2 in the 3D-HST Survey

We present evidence of large-scale outflows from three low-mass (log(M*/M☉) ~ 9.75) star-forming (SFR > 4 M☉ 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 (Wλ2796r ≳ 0.8 A) Mg II absorption systems matching precisely to the redshifts of the three galaxies. We derive the star formation surface densities from the Hα 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☉ 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 0.8 A Mg II covering fraction of star-forming galaxies at 1 0.4 A Mg II absorbing gas around star-forming galaxies may evolve from z ~ 2 to the present, consistent with recent observations of an increasing collimation of star-formation-driven outflows with time from z ~ 3.