Constraining star-formation driven outflows in local dwarf galaxies with Herschel

Galactic feedback plays a fundamental role in regulating galaxy formation and evolution, and can originate both from star formation processes and active galactic nuclei. Galaxies with low stellar mass are particularly sensitive to feedback (i.e., outflows) and offer a unique opportunity to study these phenomena in great details. Here, we investigate the physical properties of galactic outflows in a sample of 29 local low-metallicity dwarf galaxies drawn from the Dwarf Galaxy Survey. We make use of Herschel/PACS archival data to detect atomic outflows in the broad wings of observed [CII] 158 µm line profiles. We detect outflowing gas in 1/3 of the sample, and in the average galaxy population through line stacking. We find that the outflow rates of our sources are typically comparable to their star-formation rates, implying mass-loading factors (i.e., outflow efficiencies) of the order of unity. Outflow velocities are larger than the velocities required from gas to escape away from all of our targets, suggesting that a large amount of gas and dust is brought out of their halos, enriching their intergalactic medium and shaping their star-formation histories. Our results will be used as input for chemical models, posing new constraints on the processes of dust production/destruction in the interstellar medium of galaxies across cosmic time.