Bursty star formation feedback and cooling outflows

Journal article

We study how outflows of gas launched from a central galaxy undergoing repeated starbursts propagate through the circumgalactic medium (CGM), using the simulation code RAMSES. We assume that the outflow from the disk can be modelled as a rapidly moving bubble of hot gas at ~ 1 kpc above disk, then ask what happens as it moves out further into the halo around the galaxy on ~ 100 kpc scales. To do this we run 60 two-dimensional simulations scanning over parameters of the outflow. Each of these is repeated with and without radiative cooling, assuming a primordial gas composition to give a lower bound on the importance of cooling. In a large fraction of radiative-cooling cases we are able to form rapidly outflowing cool gas from in situ cooling of the flow. We show that the amount of cool gas formed depends strongly on the ‘burstiness’ of energy injection; sharper, stronger bursts typically lead to a larger fraction of cool gas forming in the outflow. The abundance ratio of ions in the CGM may therefore change in response to the detailed historical pattern of star formation. For instance, outflows generated by star formation with short, intense bursts contain up to 60 per cent of their gas mass at temperatures < 5 X 10^4 K; for near-continuous star formation the figure is ≲ 5 per cent. Further study of cosmological simulations, and of idealised simulations with e.g., metal-cooling, magnetic fields and/or thermal conduction, will help to understand the precise signature of bursty outflows on observed ion abundances.

Authors: Suarez, T; Pontzen, A; Peiris, H; Slyz, A; Devriendt, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 462
• Issue: 1
• Pages: 994-1001
• Publication date: 2016-07-01
• Acceptance date: 2016-07-08
• DOI: 10.1093/mnras/stw1670
• EISSN: 1365-2966
• ISSN: 0035-8711
• Keywords: intergalactic medium; hydrodynamics; galaxies: haloes