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Issue A&A
Volume 394, Number 2, November I 2002
Page(s) 375 - 393
Section Cosmology
DOI http://dx.doi.org/10.1051/0004-6361:20021032



A&A 394, 375-393 (2002)
DOI: 10.1051/0004-6361:20021032

The mass profile of A1413 observed with $\vec {XMM}$- $\vec {Newton}$: Implications for the M-T relation

G. W. Pratt and M. Arnaud

CEA/Saclay, Service d'Astrophysique, L'Orme des Merisiers, Bât. 709, 91191 Gif-sur-Yvette Cedex, France

(Received 27 May 2002 / Accepted 11 July 2002 )

Abstract
We present an XMM-Newton observation of A1413, a hot ( $kT = 6.5~\rm keV$ ) galaxy cluster at z=0.143. We construct gas and temperature profiles over the radial range up to ~1700 kpc. This radius corresponds to a density contrast $\delta \sim 500$ with respect to the critical density at the redshift of the cluster, or equivalently ~ 0.7 r200. The gas distribution is well described by a $\beta$ model in the outer regions, but is more concentrated in the inner ~ $250~{\rm kpc}$. We introduce a new parameterisation for the inner regions, which allows a steeper gas density distribution. The radial temperature profile does not exhibit a sharp drop, but rather declines gradually towards the outer regions, by ~ $20\%$ between 0.1 r200 and  0.5 r200. The projected temperature profile is well described by a polytropic model with $\gamma = 1.07\pm 0.01$. We find that neither projection nor PSF effects change substantially the form of the temperature profile. Assuming hydrostatic equilibrium and spherical symmetry, we use the observed temperature profile and the new parametric form for the gas density profile to produce the total mass distribution of the cluster. The mass profile is remarkably well fitted with the Moore et al.  (1999) parameterisation, implying a very centrally peaked matter distribution. The concentration parameter is in the range expected from numerical simulations. There are several indications that beyond a density contrast $\delta \sim 600$, the gas may no longer be in hydrostatic equilibrium. There is an offset with respect to adiabatic numerical simulations in the virialised part of the cluster, in the sense that the predicted mass for the cluster temperature is ~ $40\%$ too high. The gas distribution is peaked in the centre primarily as a result of the cusp in the dark matter profile. The X-ray gas to total mass ratio rises with increasing radius to $f_{\rm gas}\sim 0.2$. These data strongly support the validity of the current approach for the modeling of the dark matter collapse, but confirm that understanding the gas specific physics is essential.


Key words: galaxies: clusters: individual: A1413 -- galaxies: clusters: general -- galaxies: intergalactic medium -- cosmology: observations -- cosmology: dark matter -- X-rays: galaxies: clusters

Offprint request: G. W. Pratt, gwp@discovery.saclay.cea.fr



© ESO 2002

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