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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 308614.0, MPI für Astronomie / Publikationen_mpia
Galaxy clustering from COMBO-17:The halo occupation distribution at < z> = 0.6
Authors:Phleps, S.; Peacock, J. A.; Meisenheimer, K.; Wolf, C.
Date of Publication (YYYY-MM-DD):2006
Journal Abbrev.:Astronomy and Astrophysics
Start Page:145
End Page:155
Audience:Not Specified
Abstract / Description:We present measurements of galaxy clustering at redshift < z >=0.6 using 10 360 galaxies with photometric redshifts over an area of 0.78 deg2 from the COMBO-17 survey. To obtain a result that is unaffected by redshift uncertainties, we calculate the projected correlation function w(r_p), giving results for red sequence and blue cloud galaxies separately. The correlation function of the red galaxies displays clear deviations from a power law at comoving separations around 1 to 3{ h-1 Mpc}, and similar but weaker trends are suggested by the data for the blue galaxies. To interpret these results, we fit the correlation functions with analytical predictions derived from a simple halo occupation model. This combines linear clustering of the underlying mass with a description of the number of galaxies occupying each dark-matter halo (the halo occupation distribution). If the occupation numbers are taken to be a simple power law N ∝ M^alpha, then alpha &simeq; 0.5 and alpha &simeq; 0.2 for red and blue galaxies respectively. These figures are little different from the values required to fit present-day clustering data. The power-spectrum shape is assumed to be known in this exercise, but we allow the data to determine the preferred value of sigma_8, the linear power-spectrum normalization. The average normalization inferred from red and blue galaxies at < z >=0.6 is sigma_8=1.02±0.17 at zero redshift, consistent with independent estimates of this local value. This agreement can be regarded as a verification of the hierarchical growth of the halo mass function.
Free Keywords:large-scale structure of Universe; galaxies: statistics; cosmological parameters
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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