Virialization of the Inner CGM in the FIRE Simulations and Implications for Galaxy Disks, Star Formation, and Feedback

Stern, Jonathan; Faucher-Giguère, Claude-André; Fielding, Drummond; Quataert, Eliot; Hafen, Zachary; Gurvich, Alexander B.; Ma, Xiangcheng; Byrne, Lindsey; El-Badry, Kareem; Anglés-Alcázar, Daniel; Chan, T.K.; Feldmann, Robert; Kereš, Dušan; Wetzel, Andrew; Murray, Norman; Hopkins, Philip F.

Abstract

We use the FIRE-2 cosmological simulations to study the formation of a quasi-static, virial-temperature gas phase in the circumgalactic medium (CGM) at redshifts 0 < z < 5 and how the formation of this virialized phase affects the evolution of galactic disks. We demonstrate that when the halo mass crosses ∼1012 M⊙, the cooling time of shocked gas in the inner CGM (∼0.1Rvir, where Rvir is the virial radius) exceeds the local free-fall time. The inner CGM then experiences a transition from on average subvirial temperatures (T ≪ Tvir), large pressure fluctuations, and supersonic inflow/outflow velocities to virial temperatures (T ∼ Tvir), uniform pressures, and subsonic velocities. This transition occurs when the outer CGM (∼0.5Rvir) is already subsonic and has a temperature ∼Tvir, indicating that the longer cooling times at large radii allow the outer CGM to virialize at lower halo masses than the inner CGM. This outside-in CGM virialization scenario is in contrast with inside-out scenarios commonly envisioned based on more idealized simulations. We demonstrate that inner CGM virialization coincides with abrupt changes in the central galaxy and its stellar feedback: the galaxy settles into a stable rotating disk, star formation transitions from "bursty" to "steady," and stellar-driven galaxy-scale outflows are suppressed. Our results thus suggest that CGM virialization is initially associated with the formation of rotation-dominated thin galactic disks, rather than with the quenching of star formation as often assumed.

Citation

Stern, J., Faucher-Giguère, C.-A., Fielding, D., Quataert, E., Hafen, Z., Gurvich, A. B., Ma, X., Byrne, L., El-Badry, K., Anglés-Alcázar, D., Chan, T., Feldmann, R., Kereš, D., Wetzel, A., Murray, N., & Hopkins, P. F. (2021). Virialization of the Inner CGM in the FIRE Simulations and Implications for Galaxy Disks, Star Formation, and Feedback. Astrophysical Journal, 911(2), Article 88. https://doi.org/10.3847/1538-4357/abd776

• Journal Article Type: Article
• Acceptance Date: Dec 28, 2020
• Online Publication Date: Apr 19, 2021
• Publication Date: Apr 20, 2021
• Deposit Date: Jan 11, 2022
• Publicly Available Date: Jan 11, 2022
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 911
• Issue: 2
• Article Number: 88
• DOI: https://doi.org/10.3847/1538-4357/abd776
• Public URL: https://durham-repository.worktribe.com/output/1221004