Centrally concentrated molecular gas driving galactic-scale ionised gas outflows in star-forming galaxies

• Published in: arXiv.org 2020-12
• Main Authors: Hogarth, L M, Saintonge, A, Cortese, L, Davis, T A, Croom, S M, Bland-Hawthorn, J, Brough, S, Bryant, J J, Catinella, B, Fletcher, T J, Groves, B, Lawrence, J S, Lopez-Sanchez, A R, Owers, M S, Richards, S N, Roberts-Borsani, G W, Taylor, E N, van de Sande, J, Scott, N
• Format: Article
• Language: English
• Subjects: Carbon monoxide; Galaxy distribution; Main sequence stars; Molecular gases; Outflow; Spatial resolution; Star formation
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2011.03566

We perform a joint-analysis of high spatial resolution molecular gas and star-formation rate (SFR) maps in main-sequence star-forming galaxies experiencing galactic-scale outflows of ionised gas. Our aim is to understand the mechanism that determines which galaxies are able to launch these intense winds. We observed CO(1-0) at 1" resolution with ALMA in 16 edge-on galaxies, which also have 2" spatial resolution optical integral field observations from the SAMI Galaxy Survey. Half the galaxies in the sample were previously identified as harbouring intense and large-scale outflows of ionised gas ("outflow-types"), the rest serve as control galaxies. The dataset is complemented by integrated CO(1-0) observations from the IRAM 30-m telescope to probe the total molecular gas reservoirs. We find that the galaxies powering outflows do not possess significantly different global gas fractions or star-formation efficiencies when compared with a control sample. However, the ALMA maps reveal that the molecular gas in the outflow-type galaxies is distributed more centrally than in the control galaxies. For our outflow-type objects, molecular gas and star-formation is largely confined within their inner effective radius (\(\rm r_{eff}\)), whereas in the control sample the distribution is more diffuse, extending far beyond \(\rm r_{eff}\). We infer that outflows in normal star-forming galaxies may be caused by dynamical mechanisms that drive molecular gas into their central regions, which can result in locally-enhanced gas surface density and star-formation.