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Abstract

In this thesis we study the total mass distribution in galaxy cluster through detailed analysis of strong gravitational lensing (SL) signatures and dynamical mass information. We perform FORS2/VLT spectroscopic observations for a sample of 29 new SL selected galaxy clusters from the RCSGA survey. Our spectroscopic analysis reveals 51 lensed galaxies that correspond to 34 background sources. From the redshift measurements we derive 689 cluster members, which are used to compute velocity dispersion and dynamical masses resulting in a mass range of 0.28 ≤ M200 /e+14 Mo/h ≤ 28.4. We use these results to derive robust mass measurements of our 29 clusters by combining SL constraints with dynamical masses. We combine the best-fitting model parameters from 27 of these clusters with the recent analysis of 19 X-ray selected clusters from the CLASH survey, and also with concentration parameter measurements from 27 SL selected clusters from the SGAS survey. This leads us to the largest robust dataset of concentration parameters for a controlled sample of 73 galaxy clusters. We find that for massive clusters (M200 ~ 8 × e+14 Mo/h), the concentration parameters are distributed around c200 = 4.3 ± 1.4, which is consistent with theoretical expectations within the intrinsic scatter. In contrast, for less massive clusters (M200 ∼ 1e+14 Mo/h), the concentrations are on average almost twice the mean expected value, even if the selection bias and projection effects are taken into account, resulting in a c − M relation with a strong dependence on the cluster mass, c ∝ M^α, where α = −0.52 ± 0.09. We find that this steep mass slope is mainly due to 6 RCSGA clusters and ∼ 16 clusters from the SGAS survey that are clearly describing a higher and steeper c − M relation with c = 8.9 ± 1.12 and α = −0.69 ± 0.09. This unusual relation is far from any theoretical expectation suggesting a bimodality in the c − M relation. The rest of the sample is characterized by a mass slope of α = −0.24 ± 0.11, reconciling simulation results with observations. We also develop the first algorithm able to automatically find multiple-image systems in galaxy clusters.

Verfügbare Versionen dieser Veröffentlichung

• Mass distribution in galaxy clusters: strong lensing and dynamical mass analysis. (deposited 08 Sep. 2014 11:30)
  • Mass distribution in galaxy clusters: strong lensing and dynamical mass analysis. (deposited 08 Sep. 2014 11:27) [momentan angezeigt]