{
  "id": "1512.00559",
  "version": "v1",
  "published": "2015-12-02T03:28:24.000Z",
  "updated": "2015-12-02T03:28:24.000Z",
  "title": "Dark-ages Reionization & Galaxy Formation Simulation I: The dynamical lives of high redshift galaxies",
  "authors": [
    "Gregory B. Poole",
    "Paul W. Angel",
    "Simon J. Mutch",
    "Chris Power",
    "Alan R. Duffy",
    "Paul M. Geil",
    "Andrei Mesinger",
    "Stuart B. Wyithe"
  ],
  "comment": "15 pages, 10 figures. Submitted to MNRAS",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO"
  ],
  "abstract": "We present the Dark-ages Reionization and Galaxy-formation Observables from Numerical Simulations (DRAGONS) program and Tiamat, the collisionless N-body simulation program upon which DRAGONS is built. The primary trait distinguishing Tiamat from other large simulation programs is its density of outputs at high redshift (100 from z=35 to z=5; roughly one every 10 Myr) enabling the construction of very accurate merger trees at an epoch when galaxy formation is rapid and mergers extremely frequent. We find that the friends-of-friends halo mass function agrees well with the prediction of Watson et al. at high masses, but deviates at low masses, perhaps due to our use of a different halo finder or perhaps indicating a break from \"universal\" behaviour. We then analyse the dynamical evolution of galaxies during the Epoch of Reionization finding that only a small fraction (~20%) of galactic halos are relaxed. We illustrate this using standard relaxation metrics to establish two dynamical recovery time-scales: i) halos need ~1.5 dynamical times following formation, and ii) ~2 dynamical times following a major (3:1) or minor (10:1) merger to be relaxed. This is remarkably consistent across a wide mass range. Lastly, we use a phase-space halo finder to illustrate that major mergers drive long-lived massive phase-space structures which take many dynamical times to dissipate. This can yield significant differences in the inferred mass build-up of galactic halos and we suggest that care must be taken to ensure a physically meaningful match between the galaxy-formation physics of semi-analytic models and the halo finders supplying their input.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-12-02T03:28:24.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "high redshift galaxies",
      "galaxy formation simulation",
      "dark-ages reionization",
      "dynamical lives",
      "halo finder"
    ],
    "publication": {
      "doi": "10.1093/mnras/stw674"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 15,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1407800
    }
  }
}