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Hot-mode accretion and the physics of thin-disc galaxy formation

Hafen, Zachary; Stern, Jonathan; Bullock, James; Gurvich, Alexander B; Yu, Sijie; Faucher-Giguère, Claude-André; Fielding, Drummond B; Anglés-Alcázar, Daniel; Quataert, Eliot; Wetzel, Andrew; Starkenburg, Tjitske; Boylan-Kolchin, Michael; Moreno, Jorge; Feldmann, Robert; El-Badry, Kareem; Chan, TK; Trapp, Cameron; Kereš, Dušan; Hopkins, Philip F

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Zachary Hafen

Jonathan Stern

James Bullock

Alexander B Gurvich

Sijie Yu

Claude-André Faucher-Giguère

Drummond B Fielding

Daniel Anglés-Alcázar

Eliot Quataert

Andrew Wetzel

Tjitske Starkenburg

Michael Boylan-Kolchin

Jorge Moreno

Robert Feldmann

Kareem El-Badry

Cameron Trapp

Dušan Kereš

Philip F Hopkins


We use FIRE simulations to study disc formation in z ∼ 0, Milky Way-mass galaxies, and conclude that a key ingredient for the formation of thin stellar discs is the ability for accreting gas to develop an aligned angular momentum distribution via internal cancellation prior to joining the galaxy. Among galaxies with a high fraction (⁠>70 per cent⁠) of their young stars in a thin disc (h/R ∼ 0.1), we find that: (i) hot, virial-temperature gas dominates the inflowing gas mass on halo scales (≳20 kpc), with radiative losses offset by compression heating; (ii) this hot accretion proceeds until angular momentum support slows inward motion, at which point the gas cools to ≲104K⁠; (iii) prior to cooling, the accreting gas develops an angular momentum distribution that is aligned with the galaxy disc, and while cooling transitions from a quasi-spherical spatial configuration to a more-flattened, disc-like configuration. We show that the existence of this ‘rotating cooling flow’ accretion mode is strongly correlated with the fraction of stars forming in a thin disc, using a sample of 17 z ∼ 0 galaxies spanning a halo mass range of 1010.5 M⊙ ≲ Mh ≲ 1012 M⊙ and stellar mass range of 108 M⊙ ≲ M⋆ ≲ 1011 M⊙. Notably, galaxies with a thick disc or irregular morphology do not undergo significant angular momentum alignment of gas prior to accretion and show no correspondence between halo gas cooling and flattening. Our results suggest that rotating cooling flows (or, more generally, rotating subsonic flows) that become coherent and angular momentum-supported prior to accretion on to the galaxy are likely a necessary condition for the formation of thin, star-forming disc galaxies in a ΛCDM universe.


Hafen, Z., Stern, J., Bullock, J., Gurvich, A. B., Yu, S., Faucher-Giguère, C., …Hopkins, P. F. (2022). Hot-mode accretion and the physics of thin-disc galaxy formation. Monthly Notices of the Royal Astronomical Society, 514(4), 5056-5073.

Journal Article Type Article
Acceptance Date Jun 8, 2022
Online Publication Date Jun 14, 2022
Publication Date 2022-08
Deposit Date Jul 27, 2022
Publicly Available Date Jul 27, 2022
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 514
Issue 4
Pages 5056-5073


Published Journal Article (3.8 Mb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2022 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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