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Swirls of FIRE: Spatially Resolved Gas Velocity Dispersions and Star Formation Rates in FIRE-2 Disk Environments

Orr, Matthew E. and Hayward, Christopher C. and Medling, Anne M. and Hopkins, Philip F. and Murray, Norman and Pineda, Jorge L. and Faucher-Giguère, Claude-André and Kereš, Dušan and Su, Kung-Yi (2019) Swirls of FIRE: Spatially Resolved Gas Velocity Dispersions and Star Formation Rates in FIRE-2 Disk Environments. . (Unpublished)

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We study the spatially resolved (sub-kpc) gas velocity dispersion (σ)--star formation rate (SFR) relation in the FIRE-2 (Feedback in Realistic Environments) cosmological simulations. We specifically focus on Milky Way mass disk galaxies at late times. In agreement with observations, we find a relatively flat relationship, with σ ≈ 15−30 km/s in neutral gas across 3 dex in SFRs. We show that higher dense gas fractions (ratios of dense gas to neutral gas) and SFRs are correlated at constant σ. Similarly, lower gas fractions (ratios of gas to stellar mass) are correlated with higher σ at constant SFR. The limits of the σ-Σ_(SFR) relation correspond to the onset of strong outflows. We see evidence of "on-off" cycles of star formation in the simulations, corresponding to feedback injection timescales of 10-100 Myr, where SFRs oscillate about equilibrium SFR predictions. Finally, SFRs and velocity dispersions in the simulations agree well with feedback-regulated and marginally stable gas disk (Toomre's Q=1) model predictions, and the data effectively rule out models assuming that gas turns into stars at (low) constant efficiency (i.e., 1% per free-fall time). And although the simulation data do not entirely exclude gas accretion/gravitationally powered turbulence as a driver of σ, it appears to be strongly subdominant to stellar feedback in the simulated galaxy disks.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Orr, Matthew E.0000-0003-1053-3081
Hayward, Christopher C.0000-0003-4073-3236
Medling, Anne M.0000-0001-7421-2944
Hopkins, Philip F.0000-0003-3729-1684
Pineda, Jorge L.0000-0001-8898-2800
Faucher-Giguère, Claude-André0000-0002-4900-6628
Kereš, Dušan0000-0002-1666-7067
Su, Kung-Yi0000-0003-1598-0083
Additional Information:© 2019 The Authors. MEO is grateful for the encouragement of his late father, SRO, in studying astrophysics, and is supported by the National Science Foundation Graduate Research Fellowship under Grant No. 1144469. The Flatiron Institute is supported by the Simons Foundation. Support for AMM is provided by NASA through Hubble Fellowship grant #HST-HF2-51377 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. Support for PFH was provided by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant #1411920 and CAREER grant #1455342. CAFG was supported by NSF through grants AST-1412836 and AST-1517491, by NASA through grant NNX15AB22G, and by STScI through grants HST-AR-14293.001-A and HST-GO-14268.022-A. DK acknowledges support from the NSF grant AST-1412153 and Cottrell Scholar Award from the Research Corporation for Science Advancement. EQ was supported by NASA ATP grant 12-ATP12-0183, a Simons Investigator award from the Simons Foundation, and the David and Lucile Packard Foundation.
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1144469
Simons FoundationUNSPECIFIED
NASA Hubble FellowshipHST-HF2-51377
Alfred P. Sloan FoundationUNSPECIFIED
Cottrell Scholar of Research CorporationUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords:galaxies: ISM, evolution, formation, kinematics and dynamics, star formation, ISM: kinematics and dynamics
Record Number:CaltechAUTHORS:20200310-104835304
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101822
Deposited By: Tony Diaz
Deposited On:10 Mar 2020 17:55
Last Modified:02 Jun 2023 00:59

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