Blow-away in the Extreme Low-mass Starburst Galaxy Pox 186

Abstract

Pox 186 is an exceptionally small dwarf starburst galaxy hosting a stellar mass of ∼10⁵ M _⊙. Undetected in H i (M < 10⁶ M _⊙) from deep 21 cm observations and with an [O iii]/[O ii] (5007/3727) ratio of 18.3 ± 0.11, Pox 186 is a promising candidate Lyman continuum emitter. It may be a possible analog of low-mass reionization-era galaxies. We present a spatially resolved kinematic study of Pox 186 and identify two distinct ionized gas components: a broad one with σ > 400 km s⁻¹ and a narrow one with σ < 30 km s⁻¹. We find strikingly different morphologies between the two components and direct evidence of outflows as seen in the high-velocity gas. Possible physical mechanisms driving the creation of high-velocity gas seen in [O iii] are discussed, from outflow geometry to turbulent mixing between a hot (10⁶ K) star-cluster wind and cooler (10⁴ K) gas clouds. We find a modest mass-outflow rate of 0.022 M _⊙ yr⁻¹ with a small mass-loading factor of 0.5, consistent with other low-mass galaxies. Finally, we compare the mass-loading factor of Pox 186 with extrapolations from numerical simulations and discuss possible reasons for the apparent discrepancy between them.