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Sunyaev-Zel'dovich effect as a probe for large structures in the Universe
Image Credit: Koch et al.
Sunyaev-Zel'dovich effect as a probe for large structures in the Universe
The Sunyaev-Zel'dovich effect as a probe for large structures in the Universe. Top: integrated pressure contour map showing a signature of merger. Left: comparison between thermal and non-thermal spectral functions in a merger event. (Koch 2004, JKAS, 37,
The Sunyaev-Zel'dovich (SZ) effect is a potential probe to both detect clusters and investigate physical processes in the intra-cluster medium. The left panel shows an integrated pressure contour map for a merger perpendicular to the line-of-sight in arbitrary units. Clearly seen is the positive excess pressure around the stagnation point and the negative excess on the side due to the moving merger through the cluster gas, which serves as a signature to identify a merger in an SZ map. The middle panel shows a comparison between the thermal spectral function due to the inverse Compton scattering between hot cluster electrons and low energy CMB photons (solid curve) and the non-thermal spectral function resulting from a merger event which produces more high-relativistic electrons (dashed curve). Magnetic fields can become dynamically important in the cores of clusters of galaxies where the magnetic field pressure becomes comparable to the gas pressure. Neglecting the magnetic field can lead to an overestimation of the cluster mass of the order of 10% and subsequently to an overestimation of the SZ flux. An independent SZ measurement can thus set a limit to the magnetic field strength. The right panel shows a comparison of the radial cluster mass density profile for the case of the cluster A119, normalized by the cluster central density. The solid line is the mass profile derived with a magnetic field, whereas the dashed line shows the case neglecting the magnetic field, leading to a mass overestimation.
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