• CODEX clusters: Survey, catalog, and cosmology of the X-ray luminosity function

      Finoguenov, A.; Rykoff, E.; Clerc, N.; Costanzi, M.; Hagstotz, S.; Ider Chitham, J.; Kiiveri, K.; Kirkpatrick, C. C.; Capasso, R.; Comparat, J.; et al. (EDP SCIENCES S A, 2020-06-23)
      Context. Large area catalogs of galaxy clusters constructed from ROSAT All-Sky Survey provide the basis for our knowledge of the population of clusters thanks to long-term multiwavelength efforts to follow up observations of these clusters.Aims. The advent of large area photometric surveys superseding previous, in-depth all-sky data allows us to revisit the construction of X-ray cluster catalogs, extending the study to lower cluster masses and higher redshifts and providing modeling of the selection function.Methods. We performed a wavelet detection of X-ray sources and made extensive simulations of the detection of clusters in the RASS data. We assigned an optical richness to each of the 24 788 detected X-ray sources in the 10 382 square degrees of the Baryon Oscillation Spectroscopic Survey area using red sequence cluster finder redMaPPer version 5.2 run on Sloan Digital Sky Survey photometry. We named this survey COnstrain Dark Energy with X-ray (CODEX) clusters.Results. We show that there is no obvious separation of sources on galaxy clusters and active galactic nuclei (AGN) based on the distribution of systems on their richness. This is a combination of an increasing number of galaxy groups and their selection via the identification of X-ray sources either by chance or by groups hosting an AGN. To clean the sample, we use a cut on the optical richness at the level corresponding to the 10% completeness of the survey and include it in the modeling of the cluster selection function. We present the X-ray catalog extending to a redshift of 0.6.Conclusions. The CODEX suvey is the first large area X-ray selected catalog of northern clusters reaching fluxes of 10(-13) ergs s(-1) cm(-2). We provide modeling of the sample selection and discuss the redshift evolution of the high end of the X-ray luminosity function (XLF). Our results on z< 0.3 XLF agree with previous studies, while we provide new constraints on the 0.3< z< 0.6 XLF. We find a lack of strong redshift evolution of the XLF, provide exact modeling of the effect of low number statistics and AGN contamination, and present the resulting constraints on the flat <Lambda>CDM.
    • CODEX weak lensing mass catalogue and implications on the mass-richness relation

      Kiiveri, K.; Gruen, D.; Finoguenov, A.; Erben, T.; Van Waerbeke, L.; Rykoff, E.; Miller, L.; Hagstotz, S.; Dupke, R.; Henry, J.P.; et al. (Oxford University Press, 2021)
      The COnstrain Dark Energy with X-ray clusters (CODEX) sample contains the largest flux limited sample of X-ray clusters at 0.35 < z < 0.65. It was selected from ROSAT data in the 10 000 square degrees of overlap with BOSS, mapping a total number of 2770 high-z galaxy clusters. We present here the full results of the CFHT CODEX programme on cluster mass measurement, including a reanalysis of CFHTLS Wide data, with 25 individual lensing-constrained cluster masses. We employ lensfit shape measurement and perform a conservative colour-space selection and weighting of background galaxies. Using the combination of shape noise and an analytic covariance for intrinsic variations of cluster profiles at fixed mass due to large-scale structure, miscentring, and variations in concentration and ellipticity, we determine the likelihood of the observed shear signal as a function of true mass for each cluster. We combine 25 individual cluster mass likelihoods in a Bayesian hierarchical scheme with the inclusion of optical and X-ray selection functions to derive constraints on the slope α, normalization β, and scatter σlnλ|μ of our richness-mass scaling relation model in log-space: 〈In λ|μ〉 = αμ + β, with μ = ln (M200c/Mpiv), and Mpiv = 1014.81M⊙. We find a slope α = 0.49+0.20-0.15, normalization (β) = 84.0+9.2-14.8, and σln λ|μ = 0.17+0.13-0.09 using CFHT richness estimates. In comparison to other weak lensing richness-mass relations, we find the normalization of the richness statistically agreeing with the normalization of other scaling relations from a broad redshift range (0.0 < z < 0.65) and with different cluster selection (X-ray, Sunyaev-Zeldovich, and optical). © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
    • CODEX weak lensing: concentration of galaxy clusters at z ∼ 0.5

      Cibirka, N.; Cypriano, E. S.; Brimioulle, F.; Gruen, D.; Erben, T.; van Waerbeke, L.; Miller, L.; Finoguenov, A.; Kirkpatrick, C.; Henry, J. Patrick; et al. (OXFORD UNIV PRESS, 2017-06)
      We present a stacked weak-lensing analysis of 27 richness selected galaxy clusters at 0.40 <= z <= 0.62 in the COnstrain Dark Energy with X-ray galaxy clusters (CODEX) survey. The fields were observed in five bands with the Canada-France-Hawaii Telescope (CFHT). We measure the stacked surface mass density profile with a 14 sigma significance in the radial range 0.1 < R Mpc h(-1) < 2.5. The profile is well described by the halo model, with the main halo term following a Navarro-Frenk-White profile (NFW) profile and including the off-centring effect. We select the background sample using a conservative colour-magnitude method to reduce the potential systematic errors and contamination by cluster member galaxies. We perform a Bayesian analysis for the stacked profile and constrain the best-fitting NFW parameters M-200c = 6.6(- 0.8)(+1.0) x 10(14) h(-1)M(circle dot) and c(200c) = 3.7(+0.7) (-0.6). The off-centring effect was modelled based on previous observational results found for redMaPPer Sloan Digital Sky Survey clusters. Our constraints on M(200)c and c(200)c allow us to investigate the consistency with numerical predictions and select a concentration-mass relation to describe the high richness CODEX sample. Comparing our best-fitting values forM(200c) and c(200c) with other observational surveys at different redshifts, we find no evidence for evolution in the concentration-mass relation, though it could be mitigated by particular selection functions. Similar to previous studies investigating the X-ray luminosity-mass relation, our data suggest a lower evolution than expected from self-similarity.