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OATS-DAUT SEMINAR
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Speaker: Luca Zappacosta (INAF/OATS)

Title: Mass profiles of relaxed clusters of galaxies: an X-ray perspective

Date: Wednesday, September 26th, 2007
Time: 12:00
Venue: Villa Bazzoni

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Abstract: The density profiles of Cold Dark Matter (CDM) simulated halos have long been modeled well by an NFW profile regardless of their mass. However recent higher resolution numerical simulations and simulations employing also the baryonic physics and feedback processes do not agree with an NFW parametrization especially in the cores. Regardless of the exact density parametrization, CDM simulations produce cosmological halos whose concentration parameters correlate with mass and redshift. These relations are expected to vary significantly as a function of cosmological parameters. I will present an X-ray observation of a very relaxed cluster of galaxies for which I will show that an NFW parametrization is still a good parametrization for cluster relaxed cores at least down to 0.015 of the virial radius and that baryons in these regions do not seem to have played a role in shaping the inner dark matter density profile. Moreover using XMM and Chandra X-ray observations of relaxed galaxy systems (from ellipticals to clusters) I will show that their concentration parameter significantly correlates with mass. I will discuss the agreement with simulations and show the potentially useful indications that can be derived for cosmological models. I will then present Chandra observations of a sample of 19 distant (out to z~1.1) relaxed galaxy clusters showing that the concentration parameter also correlates with redshift at levels in marginal agreement with the CDM predictions.
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