paper

SZ polarisation as a probe of the intracluster medium

arXiv:astro-ph/0307293 · doi:10.1111/j.1365-2966.2004.07265.x

Abstract

We present high-resolution hydrodynamical simulations of the degree and direction of polarisation imprinted on the CMB by the Sunyaev-Zel'dovich effect in the the line of sight to massive galaxy clusters. We focus on two contributions which contribute most of the induced CMB polarisation in addition to the intrinsic CMB quadrupole: the radiation quadrupole seen by electrons due to their own velocity in the plane normal to the line of sight, and the radiation quadrupole due to the thermal Sunyaev-Zel'dovich effect, which is generated by a previous scattering elsewhere in the cores of the local and nearby clusters. We show that inside the virial radius of a massive cluster, this latter effect, although being second order in the optical depth, can reach the level of the former effect. These two effects can, respectively, constrain the projected tangential velocity and inner density profile of the gas, if they can be separated with multi-frequency observations. As the information on the tangential velocity of the ICM gas is combined with the kinetic Sunyaev-Zel'dovich temperature effect probing the projected radial velocity it will be possible to constrain the dynamics of the ICM. In particular, future polarisation observations may be able to trace out the filamentary structure of the cooler and less dense ionized gas that has not yet been incorporated into massive clusters. We also discuss how the collapse of a cluster should produce a peculiar ring-like polarisation pattern which would open a new window to detect proto-clusters at high redshift.

arXiv comment11 pages, 7 figures. Submitted to MNRAS. High-resolution pictures available at http://www-astro.physics.ox.ac.uk/~gxl/sz_images/. This version of the paper is accepted version by MNRAS on Sep. 7, 2003

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