Seminar @ DF-AS - P. Lopes - Optical Substructure and brightest cluster galaxy offsets of Sunyaev-Zel'dovich and X-ray Selected Galaxy Clusters

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03/28/2018 - 11:30
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03/28/2018 - 12:30
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We used optical imaging and spectroscopic data to derive substructure estimates for local Universe ($z < 0.11$) galaxy clusters from two different samples. The first was selected through the Sunyaev-Zel'dovich (SZ) effect by the Planck satellite and the second is an X-ray selected sample. In agreement to X-ray substructure estimates we found the SZ systems to have a larger fraction of substructure than the X-ray clusters. We have also found evidence that the higher mass regime of the SZ clusters, compared to the X-ray sample, explains the larger fraction of disturbed objects in the Planck data. We have also verified a good agreement ($\sim 60 \%$) between the optical and X-ray substructure estimates. However, the best level of agreement is given by the substructure classification given by measures based on the brightest cluster galaxy (BCG), either the BCG$-$X-ray offset, or the magnitude gap between the first and second BCGs. We advocate the use of those two metrics as the most reliable and cheap way to assess clusters dynamical states. However, the BCG$-$X-ray offset threshold should be smaller than typically adopted in the literature. We recommend an offset of $\sim$0.01$\times$R$_{500}$. Regarding the magnitude gap the separation can be done at $\Delta m_{12} = 1.0$.


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Last update: 03-27-2018 - 09:53