{
  "id": "1908.05274",
  "version": "v1",
  "published": "2019-08-14T18:00:00.000Z",
  "updated": "2019-08-14T18:00:00.000Z",
  "title": "Measuring dynamical masses from gas kinematics in simulated high-redshift galaxies",
  "authors": [
    "Sarah Wellons",
    "Claude-André Faucher-Giguère",
    "Daniel Anglés-Alcázar",
    "Christopher C. Hayward",
    "Robert Feldmann",
    "Philip F. Hopkins",
    "Dušan Kereš"
  ],
  "comment": "14 pages, 8 figures, submitted to MNRAS",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "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_* > 10^11 M_sun at z=1). Selecting only snapshots where a well-ordered disk is present, we calculate the rotational profile <v_phi>(r) of the cool (10^3.5 K < T < 10^4.5 K) gas and compare it to the circular velocity v_c=sqrt(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.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-08-14T18:00:00.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "gas kinematics",
      "simulated high-redshift galaxies",
      "measuring dynamical masses",
      "gas rotation accurately traces",
      "strongly bias dynamical mass measurements"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 14,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}