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Measuring dynamical masses from gas kinematics in simulated high-redshift galaxies

Wellons, Sarah and Faucher-Giguère, Claude-André and Anglés-Alcázar, Daniel and Hayward, Christopher C. and Feldmann, Robert and Hopkins, Philip F. and Kereš, Dušan (2020) Measuring dynamical masses from gas kinematics in simulated high-redshift galaxies. Monthly Notices of the Royal Astronomical Society, 497 (4). pp. 4051-4065. ISSN 0035-8711. doi:10.1093/mnras/staa2229.

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Advances in instrumentation have recently extended detailed measurements of gas kinematics to large samples of high-redshift galaxies. Relative to most nearby, thin disc galaxies, in which gas rotation accurately traces the gravitational potential, the interstellar medium (ISM) of z ≳ 1 galaxies is typically more dynamic and exhibits elevated turbulence. If not properly modelled, these effects can strongly bias dynamical mass measurements. We use high-resolution FIRE-2 cosmological zoom-in simulations to analyse the physical effects that must be considered to correctly infer dynamical masses from gas kinematics. Our analysis covers a range of galaxy properties from low-redshift Milky-Way-mass galaxies to massive high-redshift galaxies (M⋆ > 10¹¹ M⊙ at z = 1). Selecting only snapshots where a disc is present, we calculate the rotational profile v_ϕ(r) of the cool (⁠10^(3.5) < T <10^(4.5) K⁠) gas and compare it to the circular velocity v_c = √GM_(enc)/r⁠. In the simulated galaxies, the gas rotation traces the circular velocity at intermediate radii, but the two quantities diverge significantly in the centre and in the outer disc. Our simulations appear to over-predict observed rotational velocities in the centres of massive galaxies (likely from a lack of black hole feedback), so we focus on larger radii. Gradients in the turbulent pressure at these radii can provide additional radial support and bias dynamical mass measurements low by up to 40 per cent. In both the interior and exterior, the gas’ motion can be significantly non-circular due to e.g. bars, satellites, and inflows/outflows. We discuss the accuracy of commonly used analytic models for pressure gradients (or ‘asymmetric drift’) in the ISM of high-redshift galaxies.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemGIZMO code ItemAdditional data
Wellons, Sarah0000-0002-3977-2724
Faucher-Giguère, Claude-André0000-0002-4900-6628
Anglés-Alcázar, Daniel0000-0001-5769-4945
Hayward, Christopher C.0000-0003-4073-3236
Feldmann, Robert0000-0002-1109-1919
Hopkins, Philip F.0000-0003-3729-1684
Kereš, Dušan0000-0002-1666-7067
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 July 21. Received 2020 July 6; in original form 2019 August 13. Published: 06 August 2020. SW is supported by the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) at Northwestern University through the CIERA Postdoctoral Fellowship Program. CAFG was supported by NSF through grants AST-1517491, AST-1715216, and CAREER award AST-1652522; by NASA through grant 17-ATP17-0067; by STScI through grant HST-AR-14562.001; and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. DAA acknowledges support by the Flatiron Institute, which is supported by the Simons Foundation. RF acknowledges financial support from the Swiss National Science Foundation (grant no. 157591). Support for PFH was provided by an Alfred P. Sloan Research Fellowship, NSF Collaborative Research Grant No. 1715847, and CAREER grant no. 1455342, and NASA grants NNX15AT06G, JPL 1589742, and 17-ATP17-0214. DK was supported by NSF grant AST-1715101 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. Numerical calculations were run on the Quest computing cluster at Northwestern University; the Wheeler computing cluster at Caltech; XSEDE allocations TG-AST130039, TG-AST120025, TG-AST140023, and TG-AST160048; and Blue Waters PRAC allocation NSF.1713353. Data Availability: The data supporting the plots within this panels are available on reasonable request to the corresponding author. A public version of the GIZMO code is available at Additional data including simulation snapshots, initial conditions, and derived data products are available at
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA)UNSPECIFIED
Northwestern UniversityUNSPECIFIED
Cottrell Scholar of Research CorporationUNSPECIFIED
Flatiron InstituteUNSPECIFIED
Simons FoundationUNSPECIFIED
Swiss National Science Foundation (SNSF)157591
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:galaxies: evolution – galaxies: high-redshift – galaxies: ISM– galaxies: kinematics and dynamics
Issue or Number:4
Record Number:CaltechAUTHORS:20200311-130218946
Persistent URL:
Official Citation:Sarah Wellons, Claude-André Faucher-Giguère, Daniel Anglés-Alcázar, Christopher C Hayward, Robert Feldmann, Philip F Hopkins, Dušan Kereš, Measuring dynamical masses from gas kinematics in simulated high-redshift galaxies, Monthly Notices of the Royal Astronomical Society, Volume 497, Issue 4, October 2020, Pages 4051–4065,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101855
Deposited By: Tony Diaz
Deposited On:11 Mar 2020 21:19
Last Modified:16 Nov 2021 18:06

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