{
  "id": "astro-ph/9903165",
  "version": "v1",
  "published": "1999-03-11T01:11:32.000Z",
  "updated": "1999-03-11T01:11:32.000Z",
  "title": "Time Evolution of Galaxy Formation and Bias in Cosmological Simulations",
  "authors": [
    "Michael Blanton",
    "Renyue Cen",
    "Jeremiah P. Ostriker",
    "Michael A. Strauss",
    "Max Tegmark"
  ],
  "comment": "31 pages of text and figures; submitted to ApJ",
  "journal": "ApJ 531 (1999), 1",
  "doi": "10.1086/308436",
  "categories": [
    "astro-ph"
  ],
  "abstract": "The clustering of galaxies relative to the mass distribution declines with time because: first, nonlinear peaks become less rare events; second, the densest regions stop forming new galaxies because gas there becomes too hot to cool and collapse; third, after galaxies form, they are gravitationally ``debiased'' because their velocity field is the same as the dark matter. To show these effects, we perform a hydrodynamic cosmological simulation and examine the density field of recently formed galaxies as a function of redshift. We find the bias b_* of recently formed galaxies (the ratio of the rms fluctuations of these galaxies and mass), evolves from 4.5 at z=3 to around 1 at z=0, on 8 h^{-1} Mpc comoving scales. The correlation coefficient r_* between recently formed galaxies and mass evolves from 0.9 at z=3 to 0.25 at z=0. As gas in the universe heats up and prevents star formation, star-forming galaxies become poorer tracers of the mass density field. After galaxies form, the linear continuity equation is a good approximation to the gravitational debiasing, even on nonlinear scales. The most interesting observational consequence of the simulations is that the linear regression of the star-formation density field on the galaxy density field evolves from about 0.9 at z=1 to 0.35 at z=0. These effects also provide a possible explanation for the Butcher-Oemler effect, the excess of blue galaxies in clusters at redshift z ~ 0.5. Finally, we examine cluster mass-to-light ratio estimates of Omega, finding that while Omega(z) increases with z, one's estimate Omega_est(z) decreases. (Abridged)",
  "revisions": [
    {
      "version": "v1",
      "updated": "1999-03-11T01:11:32.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "cosmological simulation",
      "galaxy formation",
      "time evolution",
      "formed galaxies",
      "galaxy density field evolves"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 31,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 496558
    }
  }
}