Résumé / Abstract Journal-club_Doctorants

Journal-club Doctorants / Journal-club PhD students

« Calibrating the galaxy cluster mass scale with cluster velocity dispersions »

Stefania Amodeo
Lab. Etude Rayonnement Matière Astroph. (LERMA), Obs. Paris-Meudon (Paris, France)

The potential of galaxy clusters as cosmological probes critically depends on the capability to obtain accurate estimates of their mass. This will be a key measurement for the next generation of cosmological surveys, such as Euclid.
The disturbing discrepancy between the cosmological parameters determined from anisotropies in the cosmic microwave background and those derived from cluster abundance measurements from the Planck satellite calls for careful evaluation of the reliability of cluster mass measurements and potential systematic biases. For this purpose, it is crucial to use independent techniques based on different physical properties, like analysis of the thermal emission of the intracluster medium (ICM), observed either in the X-rays or through the Sunyaev-Zeldovich (SZ) effect, dynamics of member galaxies or gravitational lensing.
I will discuss possible bias in the Planck SZ mass proxy, which is based on X-ray observations. Using optical spectroscopy from the Gemini Multi-Object Spectrograph of seventeen Planck SZ-selected clusters, I will present new estimates of the cluster mass calibrated on the velocity dispersion of the member galaxies and independently of the ICM properties. Cluster member galaxies may not, however, share the same velocity dispersion as the bulk of the dark matter, because they are hosted by subhalos whose dynamical state may differ. I will show how this velocity bias is the primary factor limiting interpretation of dynamical cluster mass measurements at this time.
mercredi 31 mai 2017 - 17:00
Salle Entresol Daniel Chalonge, Institut d'Astrophysique
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