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Galaxy cluster number count data constraints on dark energy | | L. Campanelli
; G.L. Fogli
; T. Kahniashvili
; A. Marrone
; Bharat Ratra
; | | Date: |
11 Oct 2011 | | Abstract: | We use data on massive galaxy clusters (M_cluster > 8 10^14 h^(-1) M_solar
within a comoving radius of R_cluster = 1.5 h^(-1)Mpc) in the redshift range
0.05 < z < 0.83 to place constraints on the dark energy equation-of-state
parameters (w_0,w_a), as well as on the nonrelativistic matter density
parameter Omega_m, on the amplitude of mass fluctuations sigma_8, on the index
n of the power-law spectrum of the density perturbations, and on the Hubble
constant H_0. We show that present data weakly constrain (w_0,w_a) around the
values corresponding to a cosmological constant, i.e. (w_0,w_a) = (-1,0).
Cluster data alone prefer low values of the amplitude of mass fluctuations,
sigma_8 < 0.69 (1 sigma C.L.), and large amounts of nonrelativistic matter,
Omega_m > 0.38 (1 sigma C.L.), in slight tension with the LambdaCDM concordance
cosmological model (the results are however compatible with LambdaCDM at
2sigma). We derive a sigma_8 normalization relation, sigma_8 Omega_m^(1/3) =
0.49 pm 0.06 (2 sigma C.L.), and we find that the fit to data is almost
independent of n and only very weakly dependent on H_0. Combining cluster data
with baryon acoustic oscillation observations, cosmic microwave background
data, Hubble constant measurements, Hubble parameter determination from
passively-evolving red galaxies, and magnitude-redshift data of type Ia
supernovae, we find sigma_8 = 0.73^(+0.03)_(-0.03), Omega_m =
0.28^(+0.03)_(-0.02), w_0 = -1.14^(+0.14)_(-0.16), w_a = 0.85^(+0.42)_(-0.60),
H_0 = 69.1^(+1.3)_(-1.5) km/s/Mpc (all 1 sigma C.L. errors), in substantial
agreement with the concordance cosmological model. Very similar results are
found in the case of time-evolving dark energy with a constant
equation-of-state parameter w = const (the XCDM parametrization). Finally, we
show that the impact of bounds on (w_0,w_a) is to favor top-down phantom models
of evolving dark energy. | | Source: | arXiv, 1110.2310 | | Services: | Forum | Review | PDF | Favorites | |
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