The XXL Survey. XXV. Cosmological analysis of the C1 cluster number counts
Chiappetti, L.; Altieri, B.; Valtchanov, I.; Galli, S.; Lidman, C.; Pierre, M.; Adami, C.; Faccioli, L.; Gastaldello, F.; Poggianti, B. M.; Moscardini, L.; Birkinshaw, M.; Horellou, C.; Plionis, M.; Evrard, A. E.; Maughan, B. J.; Koulouridis, E.; Pacaud, F.; Maurogordato, S.; Alis, S.; Iovino, A.; Sereno, M.; Willis, J. P.; Melin, J. -B.; Pompei, E.; Giles, P. A.; Sadibekova, T.; Lieu, M.; Le Fèvre, J. -P.
Germany, France, United States, Italy, United Kingdom, Turkey, Spain, Sweden, Australia, Greece, Chile, Canada
Abstract
Context. We present an estimation of cosmological parameters with clusters of galaxies.
Aims: We constrain the Ωm, σ8, and w parameters from a stand-alone sample of X-ray clusters detected in the 50 deg2 XMM-XXL survey with a well-defined selection function.
Methods: We analyse the redshift distribution of a sample comprising 178 high signal-to-noise ratio clusters out to a redshift of unity. The cluster sample scaling relations are determined in a self-consistent manner.
Results: In a lambda cold dark matter (ΛCDM) model, the cosmology favoured by the XXL clusters compares well with results derived from the Planck Sunyaev-Zel'dovich clusters for a totally different sample (mass/redshift range, selection biases, and scaling relations). However, with this preliminary sample and current mass calibration uncertainty, we find no inconsistency with the Planck CMB cosmology. If we relax the w parameter, the Planck CMB uncertainties increase by a factor of 10 and become comparable with those from XXL clusters. Combining the two probes allows us to put constraints on Ωm = 0.316 ± 0.060, σ8 = 0.814 ± 0.054, and w = -1.02 ± 0.20.
Conclusions: This first self-consistent cosmological analysis of a sample of serendipitous XMM clusters already provides interesting insights into the constraining power of the XXL survey. Subsequent analysis will use a larger sample extending to lower confidence detections and include additional observable information, potentially improving posterior uncertainties by roughly a factor of 3.