Time evolution of galaxy formation and bias in cosmological simulations

Michael Blanton, Renyue Cen, Jeremiah P. Ostriker, Michael A. Strauss, Max Tegmark

    Research output: Contribution to journalArticle

    Abstract

    The clustering of galaxies relative to the underlying mass distribution declines with cosmic time for three reasons. First, nonlinear peaks become less rare events as the density field evolves. Second, the densest regions stop forming new galaxies because their gas becomes too hot to cool and collapse. Third, after galaxies form, they are subject to the same gravitational forces as the dark matter, and thus they tend to trace the dark matter distribution more closely with time; in this sense, they are gravitationally "debiased." In order to illustrate these effects, we perform a large-scale hydrodynamic cosmological simulation of a A cold dark matter (ACDM) model with Ω0 = 0.37 and examine the statistics of δ*(r, z), the density field of recently formed galaxies at position r and redshift z. We find that the bias of recently formed galaxies b* ≡ <δ2 *>1/2/<δ 2>1/2, where δ is the mass overdensity, evolves from b* ∼ 4.5 at z = 3 to B* ∼ 1 at z = 0, on 8 h-1 Mpc comoving scales. The correlation coefficient r* ≡ <δδ*>/<δ2> 1/2* 1/2 evolves from r * ∼ 0.9 at z = 3 to r* ∼ 0.3 at z = 0. That is, as gas in the universe heats up and prevents star formation, the star-forming galaxies become poorer tracers of the mass density field. We show that the linear continuity equation is a good approximation for describing the gravitational debiasing, even on nonlinear scales. The most interesting observational consequence of the simulations is that the linear regression of the galaxy formation density field on the galaxy density field, b*gr*g = <δ*δg>/<δ2 g>, evolves from about 0.9 at z = 1 to 0.35 at z = 0. Measuring this evolution, which should be possible using the Sloan Digital Sky Survey, would place constraints on models for galaxy formation. In addition, we evaluate the effects of the evolution of galaxy formation on estimates of Ω from cluster mass-to-light ratios, finding that while Ω(z) increases with z, the estimate Ωest(z) actually decreases. This effect is due to the combination of galaxy bias and the relative fading of cluster galaxies with respect to field galaxies. Finally, these effects provide a possible explanation for the Butcher-Oemler effect, the excess of blue galaxies in clusters at redshift z ∼ 0.5.

    Original languageEnglish (US)
    Pages (from-to)1-16
    Number of pages16
    JournalAstrophysical Journal
    Volume531
    Issue number1 PART 1
    StatePublished - Mar 1 2000

    Fingerprint

    galactic evolution
    galaxies
    simulation
    dark matter
    gas
    hydrodynamics
    tracer
    effect
    mass to light ratios
    continuity equation
    fading
    estimates
    mass distribution
    gases
    correlation coefficients
    tracers
    star formation
    regression analysis
    universe
    statistics

    Keywords

    • Cosmology: theory
    • Galaxies: clusters: general
    • Galaxies: formation

    ASJC Scopus subject areas

    • Space and Planetary Science

    Cite this

    Blanton, M., Cen, R., Ostriker, J. P., Strauss, M. A., & Tegmark, M. (2000). Time evolution of galaxy formation and bias in cosmological simulations. Astrophysical Journal, 531(1 PART 1), 1-16.

    Time evolution of galaxy formation and bias in cosmological simulations. / Blanton, Michael; Cen, Renyue; Ostriker, Jeremiah P.; Strauss, Michael A.; Tegmark, Max.

    In: Astrophysical Journal, Vol. 531, No. 1 PART 1, 01.03.2000, p. 1-16.

    Research output: Contribution to journalArticle

    Blanton, M, Cen, R, Ostriker, JP, Strauss, MA & Tegmark, M 2000, 'Time evolution of galaxy formation and bias in cosmological simulations', Astrophysical Journal, vol. 531, no. 1 PART 1, pp. 1-16.
    Blanton M, Cen R, Ostriker JP, Strauss MA, Tegmark M. Time evolution of galaxy formation and bias in cosmological simulations. Astrophysical Journal. 2000 Mar 1;531(1 PART 1):1-16.
    Blanton, Michael ; Cen, Renyue ; Ostriker, Jeremiah P. ; Strauss, Michael A. ; Tegmark, Max. / Time evolution of galaxy formation and bias in cosmological simulations. In: Astrophysical Journal. 2000 ; Vol. 531, No. 1 PART 1. pp. 1-16.
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