Evidence of outflow-driven gas and dust enrichment in the surroundings of dwarf galaxies

The evolution of dwarf galaxies can be largely affected by galactic outflows, which can deprive their hosts' interstellar medium (ISM) of the material needed for the formation of new stars, simultaneously enriching their surrounding circumgalactic medium (CGM) with gas and dust. Such a feedback 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 ISM. We compared, for the first time, the average spatial distributions of atomic gas, dust, and stars in and around local dwarf galaxies by stacking their [CII] 158 μm line, far-infrared, and near-UV emission, respectively. We found that gas and dust are more extended than the stellar continuum, reaching radii up to ~7 kpc, with a gas(dust) over stellar ratio of ~1.2. This is similar to what is typically observed for z > 4 star-forming galaxies, whose gas reservoirs' origin in the CGM is still debated. We attribute the extended [CII] and dust continuum emission in the CGM of our dwarf galaxies to the presence of galactic outflows. As local dwarf galaxies are considered analogs of primordial sources, we could expect that comparable feedback processes can be at the origin of the observed [CII] halos at z > 4, dominating over other possible formation mechanisms. These results will be crucial for tuning cosmological simulations attempting to reproduce the processes ruling the evolution of dwarf galaxies across cosmic time.