A z~1 galactic-scale outflow transversally mapped to ~50 kpc through gravitational-arc tomography

We report spatially resolved measurements of cool gas traced by and absorption in the circumgalactic medium (CGM) of a star-forming galaxy at z and line-of-sight velocity dispersions of (G1). The fortuitous alignment of a background gravitational arc at z absorption lines along both types of sightlines, revealing a large-scale collimated wind. We measured blueshifted line-of-sight velocities of provides seven closely spaced (sim6 kpc) transverse sightlines along the minor axis of G1, probing its CGM out to sim50 kpc. This geometry allowed us to detect a galactic-scale outflow simultaneously in the down-the-barrel and transverse directions, where we detected blueshifted v_ los ∼ 62 239 -- σ_ los ∼ 53 133 --, suggesting a structure dominated by bulk motion. De-projection of v_ los along the minor axis indicates that the outflow material barely approaches the escape velocity and is likely to be gravitationally bound to G1. We constrained an outflow opening angle þetac∼ 18^̧irc 25^̧irc, and a mass outflow rate of _ -- M out !≳!0. 06 M_⊙, ^ yr -1, corresponding to a mass loading factor η!≳!0. 004, estimated within sim10 50 kpc (sim0. 05 0. 3 R_ equivalent width and impact parameter, while also diminishing possible excess of equivalent width towards the minor axis. -- -- of the galaxy centre. Our measurements, combined with previous arc tomography data along the major axis, indicate that normalizing impact parameters by galaxy B-band luminosity substantially reduces scatter in the established anti-correlation between