2019ApJ...879....7R

We perform a Very Large Telescope FOcal Reducer and low-dispersion Spectrograph 2 narrowband imaging search around five star-forming galaxies at redshift z = 0.67-0.69 in the Great Observatories Origins Deep Survey South field to constrain the radial extent of large-scale outflows traced by resonantly scattered Mg II emission. The sample galaxies span star formation rates in the range 4M_☉yr^–1< SFR< 40M_☉yr^–1 and have stellar masses 9.9≲logM_*/M_☉≲11.0, and exhibit outflows traced by Mg II absorption with velocities ∼150–420kms^–1. These observations are uniquely sensitive, reaching surface brightness limits of 5.81 x 10^–19 erg s^–1 cm^–2 arcsec² per 1 arcsec² aperture (at 5σ significance). We do not detect any extended emission around any of the sample galaxies, thus placing 5σ upper limits on the brightness of extended Mg II emission of <6.51 x 10^–19 erg s^–1 cm^–2 arcsec² at projected distances R_⊥ > 8-21 kpc. The imaging also resolves the Mg II absorption observed toward each galaxy spatially, revealing approximately constant absorption strengths across the galaxy disks. In concert with radiative transfer models predicting the surface brightness of Mg II emission for a variety of simple wind morphologies, our detection limits suggest that either (1) the extent of the Mg II-emitting material in the outflows from these galaxies is limited to <=20 kpc; or (2) the outflows are anisotropic and/or dusty.