Abundance and Clustering of CIV Absorption Systems and the Recipe for Dark Matter
Abstract
We studied constraints on models of structure formation from the spatial number density and the correlation function of C IV absorption systems in QSO spectra. By considering a spherical model of gravitational clustering, we developed an approximate expression of the correlation function of collapsed halos in the PressSchechter formalism. The biasing of the halo correlations with respect to the mass correlation is introduced by assuming that no collapsed halo with mass M exists in uncollapsed regions with mass less than M. Since both the abundance and clustering of halos depend on their mass, to combine the two tests will reduce uncertainties caused by our poor knowledge on the mass and size of the systems identified in onedimensional samples. We found that the models of the standard cold dark matter (SCDM) and the lowdensity flat universe with a cosmological constant Lambda_0 (LCDM) would be able to explain both the observations under proper parameters, especially, if the mass of collapsed halos is chosen above or equal to 10(12.5) M_{sun}. However, the two cold plus hot dark matter models (CHDMs) with the mass parameters (Omega_c +Omega_b )/Omega_h =0.7/0.3 and 0.8/0.2 appear in difficulty to pass the two tests simultaneously. In these models, the mass of the halos should be as low as 10(11) \ M_{sun} in order to have enough collapsed halos hosting the CIV systems. But in order to match with the correlation of the CIV systems on the scales of Delta v ~ 300  1,000 km/s, the mass of the halos should be larger than 10(12) \ M_{sun}.
 Publication:

American Astronomical Society Meeting Abstracts
 Pub Date:
 December 1995
 Bibcode:
 1995AAS...187.8507B