Properties of Polarized Synchrotron Emission from Fluctuation Dynamo Action — II. Effects of Turbulence Driving in the ICM and Beam Smoothing. (arXiv:2108.13945v2 [astro-ph.GA] UPDATED)

Properties of Polarized Synchrotron Emission from Fluctuation Dynamo Action — II. Effects of Turbulence Driving in the ICM and Beam Smoothing. (arXiv:2108.13945v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Basu_A/0/1/0/all/0/1">Aritra Basu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sur_S/0/1/0/all/0/1">Sharanya Sur</a>

Polarized synchrotron emission from the radio halos of diffuse intracluster
medium (ICM) in galaxy clusters are yet to be observed. To investigate the
expected polarization in the ICM, we use high resolution ($1$,kpc)
magnetohydrodynamic simulations of fluctuation dynamos, which produces
intermittent magnetic field structures, for varying scales of turbulent driving
($l_{rm f}$) to generate synthetic observations of the polarized emission. We
focus on how the inferred diffuse polarized emission for different $l_{rm f}$
is affected due to smoothing by a finite telescope resolution. The mean
fractional polarization $langle prangle$ vary as $langle p rangle propto
l_{rm f}^{1/2}$ with $langle p rangle > 20%$ for $l_{rm f} gtrsim
60$,kpc, at frequencies $nu > 4,{rm GHz}$. Faraday depolarization at $nu <
3$,GHz leads to deviation from this relation, and in combination with beam
depolarization, filamentary polarized structures are completely erased,
reducing $langle p rangle$ to below 5% level at $nu lesssim1$,GHz.
Smoothing on scales up to $30$,kpc reduces $langle p rangle$ above $4$,GHz
by at most a factor of 2 compared to that expected at $1$,kpc resolution of
the simulations, especially for $l_{rm f} gtrsim 100$,kpc, while at $nu <
3$,GHz, $langle p rangle$ is reduced by a factor of more than 5 for $l_{rm
f} gtrsim 100$,kpc, and by more than 10 for $l_{rm f} lesssim 100$,kpc.
Our results suggest that observational estimates of, or constrain on, $langle
p rangle$ at $nu gtrsim 4$,GHz could be used as an indicator of the
turbulent driving scale in the ICM.

Polarized synchrotron emission from the radio halos of diffuse intracluster
medium (ICM) in galaxy clusters are yet to be observed. To investigate the
expected polarization in the ICM, we use high resolution ($1$,kpc)
magnetohydrodynamic simulations of fluctuation dynamos, which produces
intermittent magnetic field structures, for varying scales of turbulent driving
($l_{rm f}$) to generate synthetic observations of the polarized emission. We
focus on how the inferred diffuse polarized emission for different $l_{rm f}$
is affected due to smoothing by a finite telescope resolution. The mean
fractional polarization $langle prangle$ vary as $langle p rangle propto
l_{rm f}^{1/2}$ with $langle p rangle > 20%$ for $l_{rm f} gtrsim
60$,kpc, at frequencies $nu > 4,{rm GHz}$. Faraday depolarization at $nu <
3$,GHz leads to deviation from this relation, and in combination with beam
depolarization, filamentary polarized structures are completely erased,
reducing $langle p rangle$ to below 5% level at $nu lesssim1$,GHz.
Smoothing on scales up to $30$,kpc reduces $langle p rangle$ above $4$,GHz
by at most a factor of 2 compared to that expected at $1$,kpc resolution of
the simulations, especially for $l_{rm f} gtrsim 100$,kpc, while at $nu <
3$,GHz, $langle p rangle$ is reduced by a factor of more than 5 for $l_{rm
f} gtrsim 100$,kpc, and by more than 10 for $l_{rm f} lesssim 100$,kpc.
Our results suggest that observational estimates of, or constrain on, $langle
p rangle$ at $nu gtrsim 4$,GHz could be used as an indicator of the
turbulent driving scale in the ICM.

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