Environmental influences on dark matter haloes and consequences for the galaxies within them

Monthly Notices of the Royal Astronomical Society (Impact Factor: 5.52). 12/1998; 302(1):111 - 117. DOI: 10.1046/j.1365-8711.1999.02090.x
Source: arXiv

ABSTRACT We use large N-body simulations of dissipationless gravitational clustering in cold dark matter (CDM) cosmologies to study whether the properties of dark matter haloes are affected by their environment. We look for correlations between the masses, formation redshifts, concentrations, shapes and spins of haloes and the overdensity of their local environment. We also look for correlations of these quantities with the local tidal field. Our conclusion is extremely simple. Only the mass distribution varies as a function of environment. This variation is well described by a simple analytic formula based on the conditional Press--Schechter theory. We find no significant dependence of any other halo property on environment. Our results do not depend on our choice of cosmology. According to current hierarchical models, the structure and evolutionary history of a galaxy are fully determined by the structure and evolutionary history of the dark halo in which it is embedded. If these models are correct, clustering variations between galaxies of differing morphological types, luminosities, colours and surface brightnesses must all arise because the halo mass function is skewed towards high-mass objects in overdense regions of the Universe and towards low-mass objects in underdense regions.

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    ABSTRACT: Aims: We present an adaptation of the standard scenario of disk-galaxy formation to the concordant LambdaCDM cosmology aimed to derive analytical expressions for the scale length and rotation speed of present-day disks that form within four different, cosmologically motivated protogalactic dark matter halo-density profiles. Methods: We invoke a standard galaxy-formation model that includes virial equilibrium of spherical dark halos, specific angular momentum conservation during gas cooling, and adiabatic halo response to the gas inflow. The mean mass-fraction and mass-to-light ratio of the central stellar disk are treated as free parameters whose values are tuned to match the zero points of the observed size-luminosity and circular speed-luminosity relations of galaxies. Results: We supply analytical formulas for the characteristic size and rotation speed of disks built inside Einasto r1/6, Hernquist, Burkert, and Navarro-Frenk-White dark matter halos. These expressions match simultaneously the observed zero points and slopes of the different correlations that can be built in the RVL space of disk galaxies from plausible values of the galaxy- and star-formation efficiencies.
    Astronomy and Astrophysics 06/2010; 516. · 4.48 Impact Factor
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    ABSTRACT: We generate mock galaxy catalogues for a grid of different cosmologies, using rescaled N-body simulations in tandem with a semi-analytic model run using consistent parameters. Because we predict the galaxy bias, rather than fitting it as a nuisance parameter, we obtain an almost pure constraint on sigma8 by comparing the projected two-point correlation function we obtain to that from the Sloan Digital Sky Survey (SDSS). A systematic error arises because different semi-analytic modelling assumptions allow us to fit the r-band luminosity function equally well. Combining our estimate of the error from this source with the statistical error, we find sigma8 = 0.97 +/- 0.06. We obtain consistent results if we use galaxy samples with a different magnitude threshold, or if we select galaxies by bJ-band rather than r-band luminosity and compare to data from the 2dF Galaxy Redshift Survey (2dFGRS). Our estimate for sigma8 is higher than that obtained for other analyses of galaxy data alone, and we attempt to find the source of this difference. We note that in any case, galaxy clustering data provide a very stringent constraint on galaxy formation models.
    Monthly Notices of the Royal Astronomical Society 12/2007; 382:1503-1515. · 5.23 Impact Factor

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Gerard Lemson