TY - JOUR
T1 - Virialization of the inner CGM in the FIRE simulations and implications for galaxy disks, star formation, and feedback
AU - Stern, Jonathan
AU - Faucher-Giguère, Claude André
AU - Fielding, Drummond
AU - Quataert, Eliot
AU - Hafen, Zachary
AU - Gurvich, Alexander B.
AU - Ma, Xiangcheng
AU - Byrne, Lindsey
AU - El-Badry, Kareem
AU - Anglés-Alcázar, Daniel
AU - Chan, T. K.
AU - Feldmann, Robert
AU - Kereš, Dušan
AU - Wetzel, Andrew
AU - Murray, Norman
AU - Hopkins, Philip F.
N1 - Publisher Copyright:
© 2021. The American Astronomical Society. All rights reserved.
PY - 2021/4/20
Y1 - 2021/4/20
N2 - 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 Me, 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.
AB - 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 Me, 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.
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U2 - 10.3847/1538-4357/abd776
DO - 10.3847/1538-4357/abd776
M3 - Article
AN - SCOPUS:85105594182
SN - 0004-637X
VL - 911
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 88
ER -