Spatially-resolved chemodynamics of the starburst dwarf galaxy CGCG 007-025: Evidence for recent accretion of metal-poor gas

TL;DR

This study uses integral field spectroscopy to analyze the chemodynamics of the dwarf galaxy CGCG 007-025, revealing recent accretion of metal-poor gas that fuels starburst activity and influences its metallicity distribution.

Contribution

First detailed chemodynamical analysis of a nearby starburst dwarf galaxy using VLT/MUSE data, highlighting recent metal-poor gas accretion as a starburst trigger.

Findings

Gas-phase metallicity varies by 0.6 dex across the galaxy.

Anti-correlation between star formation rate and metallicity.

Evidence of energetic outflows from massive stars.

Abstract

Nearby metal-poor starburst dwarf galaxies present a unique opportunity to probe the physics of high-density star formation with a detail and sensitivity unmatched by any observation of the high-z Universe. Here we present the first results from a chemodynamical study of the nearby, gas-rich starburst dwarf CGCG 007-025. We use VLT/MUSE integral field spectroscopy to characterise the properties of the star-forming (SF) gas, from its metal content to its kinematics. The star formation rate (SFR) surface density presents a clumpy distribution, with the brightest knot hosting a 5 Myr young, Wolf-Rayet (WR) population (revealed by the presence of the characteristic 5808\AA~WR bump). The ionised gas kinematics are dominated by disordered motions. A superposition of a narrow ($\sigma \approx$ 50 km s$^{-1}$), intermediate (150 km s$^{-1}$) and broad (1000 km s$^{-1}$) kinematic components are needed to model the emission line profiles in the brightest SF region, suggesting the presence of energetic outflows from massive stars. The gas-phase metallicity of the galaxy spans 0.6 dex and displays a strong anti-correlation with SFR surface density, dropping to 12+log(O/H) = 7.7 in the central SF knot. The spatially-resolved BPTs indicates the gas is being ionised purely by SF processes. Finally, the anti-correlation between the SFR and the gas metallicity points out to accretion of metal-poor gas as the origin of the recent off-centre starburst, in which the infalling material ignites the SF episode.