{
  "id": "1405.0516",
  "version": "v1",
  "published": "2014-05-02T21:09:44.000Z",
  "updated": "2014-05-02T21:09:44.000Z",
  "title": "Evolution of Cold Streams and Emergence of the Hubble Sequence",
  "authors": [
    "Renyue Cen"
  ],
  "comment": "12 pages, 5 figures, submitted to ApJ Letters",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "A new physical framework for the emergence of the Hubble sequence is outlined, based on novel analyses performed to quantify the evolution of cold streams of a large sample of galaxies from a state-of-the-art ultra-high resolution, large-scale adaptive mesh-refinement hydrodynamic simulation in a fully cosmological setting. It is found that the following three key physical variables of galactic cold inflows crossing the virial sphere substantially decrease with decreasing redshift: the number of streams N_{90} that make up 90% of concurrent inflow mass flux, average inflow rate per stream dot M_{90} and mean (mass flux weighted) gas density in the streams n_{gas}. Another key variable, the stream dimensionless angular momentum parameter lambda, instead is found to increase with decreasing redshift. Assimilating these trends and others leads naturally to a physically coherent scenario for the emergence of the Hubble sequence, including the following expectations: (1) the predominance of a mixture of disproportionately small irregular and complex disk galaxies at z>2 when most galaxies have multiple concurrent streams, (2) the beginning of the appearance of flocculent spirals at z~1-2 when the number of concurrent streams are about 2-3, (3) the grand-design spiral galaxies appear at z<1 when galaxies with only one major cold stream significantly emerge. These expected general trends are in good accord with observations. Early type galaxies are those that have entered a perennial state of zero cold gas stream, with their abundance increasing with decreasing redshift.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2014-05-02T21:09:44.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "hubble sequence",
      "angular momentum parameter lambda",
      "dimensionless angular momentum parameter",
      "adaptive mesh-refinement hydrodynamic simulation",
      "decreasing redshift"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/2041-8205/789/1/L21",
      "journal": "The Astrophysical Journal",
      "year": 2014,
      "month": "Jul",
      "volume": 789,
      "number": 1
    },
    "note": {
      "typesetting": "TeX",
      "pages": 12,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1294202,
      "adsabs": "2014ApJ...789L..21C"
    }
  }
}