Weak lensing analysis of CODEX clusters using dark energy camera legacy survey : mass-richness relation

We present the weak-lensing analysis of 279 CODEX clusters using imaging data from 4200 deg(2) of the DECam Legacy Survey (DECaLS) Data Release 3. The cluster sample results from a joint selection in X-ray, optical richness in the range 20 proportional to M-0 (lambda/40)(F lambda). By measuring the CODEX cluster sample as an individual cluster, we obtain the best-fitting values, M-0 = 3.24(-0.27)(+0.29) x 10(14)M(circle dot), and F-lambda = 1.00(-0.22)(+0.22) for the richness scaling index, consistent with a power-law relation. Moreover, we separate the cluster sample into three richness groups; lambda = 20-30, 30-50, and 50-110, and measure the stacked excess surface mass density profile in each group. The results show that both methods are consistent. In addition, we find an excellent agreement between our weak lensing based scaling relation and the relation obtained with dynamical masses estimated from cluster member velocity dispersions measured by the SDSS-IV/SPIDERS team. This suggests that the cluster dynamical equilibrium assumption involved in the dynamical mass estimates is statistically robust for a large sample of clusters.Peer reviewe

Estimation de masse des amas de galaxies massifs avec les lentilles gravitationnelles dans le régime faible

Dans cette thèse, j’entreprend l'analyse en lentilles faibles de 279 amas de galaxies du relevé “COnstrain Dark Energy avec X-ray” (CODEX), à l'aide de données d'imagerie provenant des 4200 deg2 du relevé DECam Legacy Survey (DECaLS). Cet échantillon est issus d'une sélection conjointe en rayons X et en richesse optique, dans un intervalle de richesse 20 ≤ λ < 110 et de décalage vers le rouge 0,1 ≤ z ≤ 0,2. Je sépare l’échantillon en trois intervalles de richesse, λ = 20 - 30, 30 - 50 et 50 - 110. Je mesure l’excès de densité surfacique de masse cumulée et l’ajuste avec un profil NFW afin d’estimer la masse moyenne des amas dans chaque intervalle de richesse. De plus, j'étudie la relation d'échelle entre la masse (M 200c) et la richesse en supposant la relation (M 200c | λ rangle α M0 , (λ / 40) F λ . Je réalise un ajustement conjoint de toutes les mesures en lentille faible pour les amas individuels, et j’obtiens les valeurs de meilleur ajustement M {0} = 3,24 +0,29 - 0,27 times 10 14 text M {\odot} et F λ = 1,00 {+0.22} {-0.22}. Je trouve un excellent accord entre la relation d’échelle basée sur les lentilles faibles et la relation obtenue avec les masses dynamiques, ce qui pourrait suggérer que l'hypothèse d'équilibre dynamique qui sous-tend l'estimation de la masse dynamique des amas de galaxies est correcte en moyenne.In this work, I perform the weak lensing analysis of 279 galaxy clusters from the COnstrain Dark Energy with X-ray survey (CODEX), using imaging data from 4200 deg2 of the DECam Legacy Survey (DECaLS) Data Release 3. The CODEX cluster sample is built from a joint X-ray and optical richness selection. I select clusters in the richness range 20 ≤ λ < 110 and in the redshift range 0,1 ≤ z ≤ 0,2. I divide the cluster sample into three richness groups; λ = 20 - 30, 30 - 50 et 50 - 110. I measure the stacked excess surface mass density and fit it with a NFW profile to extract the mean cluster mass in each group. Moreover, I study the scaling relation between the cluster mass (M 200c) and the richness by assuming the mass-richness relation follows \left\langle M 200c | λ \right\rangle \propto M 0 , (λ / 40) F λ. I perform a joint fit of all the individual cluster weak lensing signal, and obtain the best-fit values, M 0 = 3.24 +0.29 - 0.27} \times 10 4 \text{M}_{\odot}, and F λ = 1.00 ^{+0.22}_{-0.22} for the richness scaling index. I find the resulting scaling relation to be in agreement with the mass estimates obtained for the three richness groups, thus confirming the validity of the power-law model assumption. I find an excellent agreement between the weak lensing based scaling relation and the relation obtained with dynamical masses, which might suggest that the dynamical equilibrium assumption underlying the dynamical mass estimation of galaxy clusters is correct on averag