Improvements in the X-ray luminosity function and constraints on the cosmological parameters from X-ray luminous clusters

¹ Dipartimento di Fisica e Astronomia, Università di Catania, Viale Andrea Doria 6, 95125 Catania, Italy e-mail: antonino.delpopolo@unibg.it
² Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
³ Dipartimento di Metodologie Chimiche e Fisiche per l'Ingegneria, Univesità di Catania, Viale A. Doria 6, 95125, Catania, Italy
⁴ Osservatorio Astrofisico di Catania, Istituto Nazionale di Astrofisica, via S. Sofia 78, 95123, Catania, Italy

Received: 17 August 2009
Accepted: 31 December 2010

Abstract

Aims. We improve the current constraints on Ω_m, the dark-energy equation-of-state parameter, w, and σ₈, obtained from measurements of the X-ray luminosity function of galaxy clusters, namely MACS, the local BCS, and the REFLEX galaxy cluster samples with luminosities L > 3 × 10⁴⁴ erg/s in the 0.1–2.4 keV band.

Methods. To this aim, we use Tinker and collaborators mass function instead of Jenkins and collaborators and the mass-luminosity relationship obtained by Del Popolo and collaborators.

Results. Using the same methods and priors as Mantz and collaborators, we find Ω_m = and σ₈ = , for a ΛCDM universe, while the result of Mantz and collaborators gives less tight constraints Ω_m = and σ₈ = . In the case of a wCDM model, we find Ω_m = , σ₈ = and w = , while in Mantz and collaborators they are again less tight Ω_m = , σ₈ = and w = . Combining the XLF analysis with the f_gas+CMB+SNIa data set results in the constraint Ω_m = 0.269  ±  0.012, σ₈ = 0.81  ±  0.021 and w = -1.02  ±  0.04, to be compared with Mantz and collaborators, Ω_m = 0.269  ±  0.016, σ₈ = 0.82  ±  0.03 and w = -1.02  ±  0.06. The tightness of the last constraints obtained by Mantz and collaborators, are fundamentally due to the tightness of the f_gas+CMB+SNIa constraints and not to their XLF analysis. Our findings, consistent with w = -1, lend additional support to the cosmological-constant model.