The Relative Abundance of Isolated Clusters as a Probe of Dark Energy
Abstract
Those galaxy clusters that do not belong to superclusters are referred to as isolated clusters. Their relative abundance at a given epoch may be a powerful constraint of the dark energy equation of state since it depends strongly on how fast the structures grow on the largest scale in the universe. We note that the mass function of isolated clusters can be separately evaluated through modification of the recently developed Corasaniti-Achitouv (CA) theory according to which the stochastic collapse barrier is quantified by two coefficients: the drifting average coefficient (β) and the diffusion coefficient (DB ). Regarding β in the CA formalism as an adjustable parameter and assuming that the formation of isolated clusters corresponds to the case of DB = 0, we determine the mass function of isolated clusters by fitting the numerical results from the MICE simulations to the modified CA formula. It is found that the best-fit value of β changes with redshift and that the CA mass function with DB = 0 agrees very well with the numerical results at various redshifts. Defining the relative abundance of isolated clusters, ξ I , as the ratio of the cumulative mass function of isolated clusters to that of non-isolated clusters at a given epoch, we finally show how sensitively ξ I changes with the dark energy equation of state. It is also discussed how ξ I can help break the degeneracy between the dark energy equation of state and the other key cosmological parameters.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2012
- DOI:
- 10.1088/0004-637X/752/1/40
- arXiv:
- arXiv:1108.1712
- Bibcode:
- 2012ApJ...752...40L
- Keywords:
-
- cosmology: theory;
- large-scale structure of universe;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- accepted for publication in ApJ, isolated-to-nonisolated ratio plots at a fixed mass scale additionally shown, discussion improved, mistakes corrected, 7 figures, 2 tables