Stellar feedback drives the baryon deficiency in low-mass galaxies

Stellar feedback, as a key process regulating the baryon cycle, is thought to greatly redistribute baryonic material inside and outside the dark matter halos (DMHs); however, the observational evidences are lacking. Through stacking analyses of ∼400,000 galaxy spectra from Dark Energy Spectroscopic Instrument (DESI), we find star formation–driven cool outflows in the Mg

absorption line. Assuming only gravity acts on the launched gas, our calculations reveal that outflows from low-mass galaxies ( M ∗ < 10 10   M ⊙ ) are capable of escaping beyond the DMHs, which aligns well with our finding in the circumgalactic medium (CGM) absorption along the minor axes of galaxies using background quasars. This research offers indirect evidence that stellar feedback drives the low baryon retention rate in low-mass halos, implicating that baryonic processes within galaxies are connected with the diffuse matter beyond the DMHs.