Shaken, but not expelled: Gentle baryonic feedback from nearby starburst dwarf galaxies

¹ INAF – Arcetri Astrophysical Observatory, Largo E. Fermi 5, 50127 Firenze, Italy
e-mail: antonino.marasco@inaf.it
² INAF – Padova Astronomical Observatory, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
³ Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Avda. Vicũna Mackenna 4860, 8970117 Macul, Santiago, Chile
⁴ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Muenchen, Germany
⁵ Dipartimento di Fisica e Astronomia, Universitá di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Firenze, Italy
⁶ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁷ Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
⁸ Institute for Computational Cosmology, Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK
⁹ AURA for the European Space Agency (ESA), Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁰ Scuola Normale Superiore, Piazza dei Cavalieri 7, Pisa 56126, Italy
¹¹ Department of Electrical Engineering and Center of Astro-Engineering UC, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile

Received: 6 September 2022
Accepted: 16 November 2022

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 10⁷ < M_⋆/M_⊙ < 10¹⁰, 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 Hα 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 10⁸ 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.