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Pressure balance in the multiphase ISM of cosmologically simulated disk galaxies

Gurvich, Alexander B. and Faucher-Giguère, Claude-André and Richings, Alexander J. and Hopkins, Philip F. and Grudić, Michael Y. and Hafen, Zachary and Wellons, Sarah and Stern, Jonathan and Quataert, Eliot and Chan, T. K. and Orr, Matthew E. and Kereš, Dušan and Wetzel, Andrew and Hayward, Christopher C. and Loebman, Sarah R. and Murray, Norman (2020) Pressure balance in the multiphase ISM of cosmologically simulated disk galaxies. . (Unpublished)

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Pressure balance plays a central role in models of the interstellar medium (ISM), but whether and how pressure balance is realized in a realistic multiphase ISM is not yet well understood. We address this question using a set of FIRE-2 cosmological zoom-in simulations of Milky Way-mass disk galaxies, in which a multiphase ISM is self-consistently shaped by gravity, cooling, and stellar feedback. We analyze how gravity determines the vertical pressure profile as well as how the total ISM pressure is partitioned between different phases and components (thermal, dispersion/turbulence, and bulk flows). We show that, on average and consistent with previous more idealized simulations, the total ISM pressure balances the weight of the overlying gas. Deviations from vertical pressure balance increase with increasing galactocentric radius and with decreasing averaging scale. The different phases are in rough total pressure equilibrium with one another, but with large deviations from thermal pressure equilibrium owing to kinetic support in the cold and warm phases, which dominate the total pressure near the midplane. Bulk flows (e.g., inflows and fountains) are important at a few disk scale heights, while thermal pressure from hot gas dominates at larger heights. Overall, the total midplane pressure is well-predicted by the weight of the disk gas, and we show that it also scales linearly with the star formation rate surface density (Σ_SFR). These results support the notion that the Kennicutt-Schmidt relation arises because Σ_(SFR) and the gas surface density (Σ_g) are connected via the ISM midplane pressure.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Faucher-Giguère, Claude-André0000-0002-4900-6628
Hopkins, Philip F.0000-0003-3729-1684
Grudić, Michael Y.0000-0002-1655-5604
Hafen, Zachary0000-0001-7326-1736
Wellons, Sarah0000-0002-3977-2724
Quataert, Eliot0000-0001-9185-5044
Chan, T. K.0000-0003-2544-054X
Orr, Matthew E.0000-0003-1053-3081
Kereš, Dušan0000-0002-1666-7067
Wetzel, Andrew0000-0003-0603-8942
Hayward, Christopher C.0000-0003-4073-3236
Additional Information:AG is grateful to Chang-Goo Kim for very useful discussions regarding the analysis of disk equilibrium in simulations; Samantha Benincasa and Victor Robles for their helpful comments that improved the quality of this paper; and Bridget Haas for her unwavering support and encouragement during the course of the project. AG also acknowledges support from the National Science Foundation under grants DGE-0948017, DGE-145000, and DGE-1842165, and from Blue Waters as a graduate fellow which is itself supported by the National Science Foundation (awards OCI-0725070 and ACI-1238993). CAFG was supported by NSF through grants AST-1412836, AST-1517491, AST-1715216, and CAREER award AST-1652522, by NASA through grants NNX15AB22G and 17-ATP17-0067, by STScI through grants HST-GO-14681.011, HST-GO-14268.022-A, and HST-AR-14293.001-A, and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. AJR was supported by a COFUND/Durham Junior Research Fellowship under EU grant 609412 and by the Science and Technology Facilities Council [ST/P000541/1]. MYG, SW, and JS are supported as a CIERA Fellows by the CIERA Postdoctoral Fellowship Program (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University). TKC was supported by the Science and Technology Facilities Council astronomy consolidated grant ST/T000244/1. DK was supported by NSF Grant AST-1715101 and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. AW received support from NASA through ATP grant 80NSSC18K1097 and HST grants GO-14734, AR-15057, AR-15809, and GO-15902 from STScI; the Heising-Simons Foundation; and a Hellman Fellowship. Support for SRL was provided by NASA through Hubble Fellowship grant HST-JF2-51395.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. The Flatiron Institute is supported by the Simons Foundation. This research was undertaken, in part, thanks to funding from the Canada Research Chairs program. Numerical calculations were run on the Quest computing cluster at Northwestern University; the Wheeler computing cluster at Caltech; XSEDE allocations TG-AST120025, TG-AST140023, TG-AST130039, and TG-AST140064; Blue Waters PRAC allocation NSF.1713353; and NASA HEC allocation SMD16-7592, SMD-16-7561, SMD-17-1204, SMD-16-7324, and SMD-17-1375.
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-0948017
NSF Graduate Research FellowshipDGE-145000
NSF Graduate Research FellowshipDGE-1842165
Cottrell Scholar of Research CorporationUNSPECIFIED
European Research Council (ERC)609412
Science and Technology Facilities Council (STFC)ST/P000541/1
Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA)UNSPECIFIED
Science and Technology Facilities Council (STFC)ST/T000244/1
Heising-Simons FoundationUNSPECIFIED
Hellman FellowshipUNSPECIFIED
NASA Hubble FellowshipHST-JF2-51395.001-A
Simons FoundationUNSPECIFIED
Canada Research Chairs ProgramUNSPECIFIED
Subject Keywords:cosmology: theory – galaxies: evolution – galaxies: formation – galaxies: ISM – galaxies: star formation
Record Number:CaltechAUTHORS:20200626-150120381
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104100
Deposited By: George Porter
Deposited On:29 Jun 2020 17:43
Last Modified:29 Jun 2020 17:43

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