2017A&A...605A.118F

Emission signatures from galactic winds provide an opportunity to directly map the outflowing gas, but this is traditionally challenging because of the low surface brightness. Using very deep observations (27 h) of the Hubble Deep Field South with the Multi Unit Spectroscopic Explorer (MUSE) instrument, we identify signatures of an outflow in both emission and absorption from a spatially resolved galaxy at z=1.29 with a stellar mass M_*=8x10⁹M_☉, star formation rate SFR=77⁺⁴⁰_–25M_☉/yr, and star formation rate surface brightness Σ_SFR=1.6M_☉/kpc² within the [OII] λλ3727,3729 half-light radius R_1/2,[OII]=2.76±0.17kpc. From a component of the strong resonant MgII and FeII absorptions at -350km/s, we infer a mass outflow rate that is comparable to the star formation rate. We detect non-resonant FeII* emission, at λ2365, λ2396, λ2612, and λ2626, at 1.2-2.4-1.5-2.7x10^–18erg/s/cm² respectively. The flux ratios are consistent with the expectations for optically thick gas. By combining the four non-resonant FeII* emission lines, we spatially map the FeII* emission from an individual galaxy for the first time. The FeII* emission has an elliptical morphology that is roughly aligned with the galaxy minor kinematic axis, and its integrated half-light radius, R_1/2, FeII*_=4.1±0.4kpc, is 70% larger than the stellar continuum (R_1/2,*~=2.34±0.17) or the [OII] nebular line. Moreover, the FeII* emission shows a blue wing extending up to -400km/s, which is more pronounced along the galaxy minor kinematic axis and reveals a C-shaped pattern in a p-v diagram along that axis. These features are consistent with a bi-conical outflow.