{
  "id": "1407.7129",
  "version": "v3",
  "published": "2014-07-26T14:00:27.000Z",
  "updated": "2015-01-04T17:24:06.000Z",
  "title": "Four phases of angular-momentum buildup in high-z galaxies: from cosmic-web streams through an extended ring to disc and bulge",
  "authors": [
    "Mark Danovich",
    "Avishai Dekel",
    "Oliver Hahn",
    "Daniel Ceverino",
    "Joel Primack"
  ],
  "comment": "Resubmitted to MNRAS after responding to referee's comments. (27 pages, 20 figures)",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO"
  ],
  "abstract": "We study the angular-momentum (AM) buildup in high-$z$ massive galaxies using high-resolution cosmological simulations. The AM originates in co-planar streams of cold gas and merging galaxies tracing cosmic-web filaments, and it undergoes four phases of evolution. (I) Outside the halo virial radius ($R_{\\rm v}\\!\\sim\\!100\\,{\\rm kpc}$), the elongated streams gain AM by tidal torques with a specific AM (sAM) $\\sim\\!1.7$ times the dark-matter (DM) spin due to the gas' higher quadrupole moment. This AM is expressed as stream impact parameters, from $\\sim\\!0.3R_{\\rm v}$ to counter rotation. (II) In the outer halo, while the incoming DM mixes with the existing halo of lower sAM to a spin $\\lambda_{\\rm dm}\\!\\sim\\!0.04$, the cold streams transport the AM to the inner halo such that their spin in the halo is $\\sim\\!3\\lambda_{\\rm dm}$. (III) Near pericenter, the streams dissipate into an irregular rotating ring extending to $\\sim\\!0.3R_{\\rm v}$ and tilted relative to the inner disc. Torques exerted partly by the disc make the ring gas lose AM, spiral in, and settle into the disc within one orbit. The ring is observable with 30\\% probability as a damped Lyman-$\\alpha$ absorber. (IV) Within the disc, $<\\!0.1R_{\\rm v}$, torques associated with violent disc instability drive AM out and baryons into a central bulge, while outflows remove low-spin gas, introducing certain sensitivity to feedback strength. Despite the different AM histories of gas and DM, the disc spin is comparable to the DM-halo spin. Counter rotation can strongly affect disc evolution.",
  "revisions": [
    {
      "version": "v2",
      "updated": "2014-07-31T15:29:11.000Z",
      "title": "Four phases of angular-momentum buildup in high-z galaxies: from cosmic-web streams to an extended tilted ring, disc and bulge",
      "abstract": "We study the buildup of angular momentum (AM) in high-z galaxies using zoom-in hydro-cosmological simulations. The disc AM originates in a few co-planar streams of cold gas and merging galaxies tracing filaments of the cosmic web and undergo 4 phases of evolution. In phase I, outside the halo virial radius (Rv), the elongated streams gain AM by tidal torques with a specific AM (sAM) ~1.7 times that of the dark matter (DM) due to the gas' higher quadrupole moment. This AM is expressed as stream impact parameters, from ~0.3Rv to occasional counter rotation. In phase II, in the outer halo, while the incoming DM mixes with the existing halo of lower sAM to a spin $\\lambda_{\\rm dm}\\sim0.04$, the cold streams transport the AM to the inner halo such that their spin in the halo is $\\sim3\\lambda_{\\rm dm}$. In phase III, near pericenter, the streams dissipate and form a non-uniform, rotating ring extending to ~0.3Rv and tilted relative to the inner disc. Torques exerted partly by the disc make the gas ring lose AM, spiral in, and settle into the disc within one orbit. The ring is observable with 30% probability as a damped Lyman-$\\alpha$ absorber. In phase IV, within the disc, torques associated with violent disc instability drive AM out and baryons in to a central bulge, while outflows remove low-spin gas. Despite the different AM histories of gas and dark matter, the spin of the disc is only moderately smaller than that of the DM halo.",
      "comment": "25 pages, 20 figures",
      "journal": null,
      "doi": null
    },
    {
      "version": "v3",
      "updated": "2015-01-04T17:24:06.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "high-z galaxies",
      "angular-momentum buildup",
      "extended tilted ring",
      "cosmic-web streams",
      "outflows remove low-spin gas"
    ],
    "publication": {
      "doi": "10.1093/mnras/stv270",
      "journal": "Monthly Notices of the Royal Astronomical Society",
      "year": 2015,
      "month": "May",
      "volume": 449,
      "number": 2,
      "pages": 2087
    },
    "note": {
      "typesetting": "TeX",
      "pages": 27,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1308475,
      "adsabs": "2015MNRAS.449.2087D"
    }
  }
}