2021ApJ...918L..16C

We present electron temperature (T_e) maps for the edge-on system Mrk 1486, affording "direct-method" gas-phase metallicity measurements across 5.''8 (4.1 kpc) along the minor axis and 9.''9 (6.9 kpc) along the major axis. These maps, enabled by strong detections of the [O III] λ4363 auroral emission line across a large spatial extent of Mrk 1486, reveal a clear negative minor-axis T_e gradient in which temperature decreases with increasing distance from the disk plane. We find that the lowest metallicity spaxels lie near the extremes of the major axis, while the highest metallicity spaxels lie at large spatial offsets along the minor axis. This is consistent with a picture in which low-metallicity inflows dilute the metallicity at the edges of the major axis of the disk, while star formation drives metal-enriched outflows along the minor axis. We find that the outflow metallicity in Mrk 1486 is 0.20 dex (1.6 times) higher than the average insterstellar medium (ISM) metallicity, and more than 0.80 dex (6.3 times) higher than metal-poor inflowing gas, which we observe to be below 5% Z_☉. This is the first example of metallicity measurements made simultaneously for inflowing, outflowing, and inner disk ISM gas using consistent T_e-based methodology. These measurements provide unique insight into how baryon-cycle processes contribute to the assembly of a galaxy like Mrk 1486.