Blow-Away in the Extreme Low-Mass Starburst Galaxy Pox~186

TL;DR

This study investigates the ionized gas kinematics and outflows in the tiny starburst galaxy Pox 186, revealing high-velocity gas components, outflow mechanisms, and comparing observed mass-loading factors with simulations.

Contribution

It provides the first spatially resolved kinematic analysis of Pox 186, identifying distinct gas components and outflows, and discusses their implications for low-mass galaxy evolution.

Findings

Detection of two ionized gas components with different velocity dispersions.

Evidence of outflows driven by hot star-cluster winds and turbulence.

Measured mass-outflow rate and comparison with simulation predictions.

Abstract

Pox 186 is an exceptionally small dwarf starburst galaxy hosting a stellar mass of $\sim10^5$ M$_{\odot}$. Undetected in HI (M $ < 10^6$ M$_{\odot}$) from deep 21 cm observations and with an [OIII]/[OII]\ (5007/3727) ratio of 18.3 $\pm$ 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 $\sigma > 400$ \kmps, and a narrow one with $\sigma < 30$ \kmps. 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 [OIII] are discussed, from outflow geometry to turbulent mixing between a hot (10$^6$ K) star-cluster wind and cooler (10$^4$ K) gas clouds. We find a modest mass-outflow rate of 0.022 M$_{\odot}$ \ 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.