Observational evidence for anisotropic metal excess around galaxies

The exchange of matter and energy between galaxies and their surroundings drives the cosmic baryon cycle, yet mapping metal transport remains an observational challenge. While simulations predict that galactic winds escape anisotropically along minor axes, evidence for chemical enrichment in neighboring galaxies is limited. We analyze 1433 galaxy pairs from the Dark Energy Spectroscopic Instrument survey and detect a gas-phase metallicity excess of 14.6% ± 3.7% to 24.2% ± 2.6% in neighbors aligned with the minor axis of massive primary at projected separations of 15–60 kpc, qualitatively consistent with IllustrisTNG simulation. Permutation tests indicate that this excess varies from a marginal detection (>92% confidence) at closer separations (15–30 kpc) to a significant signal (>98% confidence) at intermediate separations (30–60 kpc). Here, we show that these results provide empirical constraints on galactic feedback models and are consistent with a scenario where anisotropic outflows can enrich nearby galaxies, a mechanism that complements other environmental processes. Galactic winds transport heavy elements, but their impact on neighboring galaxies is difficult to observe. Here, the authors show that neighbors aligned with primarys’ minor axis exhibit a metallicity excess, suggesting anisotropic metal enrichment.