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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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