Joint deprojection of Sunyaev-Zeldovich and X-ray images of galaxy clusters - AstrophysicsReportar como inadecuado

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Abstract: We present two non-parametric deprojection methods aimed at recovering thethree-dimensional density and temperature profiles of galaxy clusters fromspatially resolved thermal Sunyaev-Zeldovich tSZ and X-ray surface brightnessmaps, thus avoiding the use of X-ray spectroscopic data. In both methods,clusters are assumed to be spherically symmetric and modeled with an onion-skinstructure. The first method follows a direct geometrical approach. The secondmethod is based on the maximization of a single joint tSZ and X-raylikelihood function, which allows one to fit simultaneously the two signals byfollowing a Monte Carlo Markov Chain approach. These techniques are testedagainst a set of cosmological simulations of clusters, with and withoutinstrumental noise. We project each cluster along the three orthogonaldirections defined by the principal axes of the momentum of inertia tensor.This enables us to check any bias in the deprojection associated to the clusterelongation along the line of sight. After averaging over all the threeprojection directions, we find an overall good reconstruction, with a small<~10 per cent overestimate of the gas density profile. This turns into acomparable overestimate of the gas mass within the virial radius, which weascribe to the presence of residual gas clumping. Apart from this small biasthe reconstruction has an intrinsic scatter of about 5 per cent, which isdominated by gas clumpiness. Cluster elongation along the line of sight biasesthe deprojected temperature profile upwards at r<~0.2r vir and downwards atlarger radii. A comparable bias is also found in the deprojected temperatureprofile. Overall, this turns into a systematic underestimate of the gas mass,up to 10 percent. Abridged

Autor: S. Ameglio 1,2,3, S. Borgani 1,2,3, E. Pierpaoli 4, K. Dolag 5 1 Dipartimento di Astronomia dell'Universita' di Trieste


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