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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 (2019) Measuring dynamical masses from gas kinematics in simulated high-redshift galaxies. . (Unpublished)

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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 disk 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 modeled, these effects can strongly bias dynamical mass measurements. We use high-resolution FIRE-2 cosmological zoom-in simulations to analyze the physical effects that must be considered to correctly infer dynamical masses from gas kinematics. Our analysis covers a wide 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 well-ordered disk is present, we calculate the rotational profile vφ(r) of the cool (10^(3.5) K < T < 10^(4.5) K) gas and compare it to the circular velocity v_c = √(GM_(enc)/r) assuming spherical symmetry. In the simulated massive high-redshift galaxies, the gas rotation traces the circular velocity reasonably well at intermediate radii r ~ 1-3 kpc, but the two quantities diverge significantly outside that range. At larger radii, gradients in the turbulent pressure can bias dynamical mass measurements low by ~10-40%. In the interior, the assumption of a spherically-symmetric gravitational potential becomes increasingly poor owing to a massive disk component, reducing the gas rotational velocities by ≳10%. Finally, in 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:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
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:SW is supported as a CIERA Fellow by the CIERA Postdoctoral Fellowship Program (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University). 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 #1715847, and CAREER grant #1455342, and NASA grants NNX15AT06G, JPL 1589742, 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, TGAST140023, and TG-AST160048; and Blue Waters PRAC allocation NSF.1713353.
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
Northwestern UniversityUNSPECIFIED
Cottrell Scholar of Research CorporationUNSPECIFIED
Flatiron InstituteUNSPECIFIED
Simons FoundationUNSPECIFIED
Swiss National Science Foundation (SNSF)157591
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:galaxies: high-redshift – galaxies: evolution – galaxies: kinematics and dynamics – galaxies: ISM
Record Number:CaltechAUTHORS:20200311-130218946
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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:11 Mar 2020 21:19

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