Shaken, but not expelled: Gentle baryonic feedback from nearby starburst dwarf galaxies
Antonino Marasco, Francesco Belfiore, G. Cresci, Federico Lelli, Giacomo Venturi, L. K. Hunt, Alice Concas, A. Marconi, F. Mannucci, Matilde Mingozzi, Anna F. McLeod, Nimisha Kumari, Stefano Carniani, L. Vanzi, M. Ginolfi
Abstract
Baryonic feedback is expected to play a key role in regulating the star formation of low-mass galaxies by producing galaxy-scale winds associated with mass-loading factors of β ∼ 1 − 50. We test this prediction using a sample of 19 nearby systems with stellar masses of 10 7 < M ⋆ / M ⊙ < 10 10 , mostly lying above the main sequence of star-forming galaxies. We used MUSE at VLT optical integral field spectroscopy to study the warm ionised gas kinematics of these galaxies via a detailed modelling of their H α emission line. The ionised gas is characterised by irregular velocity fields, indicating the presence of non-circular motions of a few tens of km s −1 within galaxy discs, but with intrinsic velocity dispersion of 40 − 60 km s −1 that are only marginally larger than those measured in main-sequence galaxies. Galactic winds, defined as gas at velocities larger than the galaxy escape speed, encompass only a few percent of the observed fluxes. Mass outflow rates and loading factors are strongly dependent on M ⋆ , the star formation rate (SFR), SFR surface density, and specific SFR (sSFR). For M ⋆ of 10 8 M ⊙ we find β ≃ 0.02, which is more than two orders of magnitude smaller than the values predicted by theoretical models of galaxy evolution. In our galaxy sample, baryonic feedback stimulates a gentle gas cycle rather than causing a large-scale blow-out.