The primary role of star-formation-driven outflows on the baryon cycle of nearby dwarf galaxies

Feedback from stars and active galactic nuclei is one of the most important processes steering the baryon cycle in galaxies, i.e., the set of complex phenomena driving the interplay between gas, dust, and star formation in their interstellar medium (ISM). Such a feedback could be strong enough to produce galactic-scale outflows able to sweep the gas out of the galaxies, drastically shaping their evolution. We investigated the impact of star-formation-driven outflows in local, low-metallicity dwarf galaxies drawn from the Dwarf Galaxy Survey. We made use of Herschel observations to detect atomic outflowing gas in the high-velocity wings of [CII] 158 µm emission line profiles. We found that outflows are ubiquitous in these galaxies, with an average outflow efficiency of the order of unity, at odds with predictions from state-of-the-art chemical evolution models. We estimated that ~40% of the gas entrained by the outflows can be expelled from the ISM, significantly enriching the surrounding circumgalactic medium. We indeed found evidence of extended atomic gas and dust reservoirs around these galaxies and compared them with those observed by ALMA in the early Universe, pointing out their possible common origin. These results highlight the key role of stellar feedback in the baryon cycle of low-mass sources, and are crucial for calibrating cosmological simulations attempting to reproduce the processes ruling the evolution of these galaxies across cosmic time.