2021MNRAS.501.3332S -
Mon. Not. R. Astron. Soc., 501, 3332-3349 (2021/March-1)
Properties of polarized synchrotron emission from fluctuation-dynamo action - I. Application to galaxy clusters.
SUR S., BASU A. and SUBRAMANIAN K.
Abstract (from CDS):
Using magnetohydrodynamic simulations of fluctuation dynamos, we perform broad-bandwidth synthetic observations to investigate the properties of polarized synchrotron emission and the role that Faraday rotation plays in inferring the polarized structures in the intracluster medium (ICM) of galaxy clusters. In the saturated state of the dynamo, we find a Faraday depth (FD) dispersion σFD ≃ 100 rad m–2, in agreement with observed values in the ICM. Remarkably, the FD power spectrum is qualitatively similar to M(k)/k, where M(k) is the magnetic spectrum and k the wavenumber. However, this similarity is broken at high k when FD is obtained by applying rotation measure (RM) synthesis to polarized emission from the ICM due to poor resolution and complexities of spectrum in FD space. Unlike the Gaussian probability distribution function (PDF) obtained for FD, the PDF of the synchrotron intensity is lognormal. A relatively large σFD in the ICM gives rise to strong frequency-dependent variations of the pixel-wise mean and peak polarized intensities at low frequencies (≲1.5 GHz). The mean fractional polarization <p> obtained at the resolution of the simulations increases from <0.1 at 0.5 GHz to its intrinsic value of ∼0.3 at 6 GHz. Beam smoothing significantly affects the polarization properties below ≲1.5 GHz, reducing <p> to <= 0.01 at 0.5 GHz. At frequencies ≳5 GHz, polarization remains largely unaffected, even when recovered using RM synthesis. Thus, our results underline the need for high-frequency (≳5 GHz) observations with future radio telescopes to effectively probe the properties of polarized emission in the ICM.
Abstract Copyright:
© 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society
Journal keyword(s):
dynamo - MHD - turbulence - galaxies: clusters: intracluster medium - galaxies: magnetic fields
Simbad objects:
3
Full paper
View the references in ADS
To bookmark this query, right click on this link: simbad:2021MNRAS.501.3332S and select 'bookmark this link' or equivalent in the popup menu