Constraints on Large-Scale Magnetic Fields in the Intergalactic Medium Using Cross-Correlation Methods. (arXiv:2102.11312v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Amaral_A/0/1/0/all/0/1">Ariel Amaral</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vernstrom_T/0/1/0/all/0/1">Tessa Vernstrom</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gaensler_B/0/1/0/all/0/1">Bryan M. Gaensler</a>
Large-scale coherent magnetic fields in the intergalactic medium are presumed
to play a key role in the formation and evolution of the cosmic web, and in
large scale feedback mechanisms. However, they are theorized to be extremely
weak, in the nano-Gauss regime. To search for a statistical signature of these
weak magnetic fields we perform a cross-correlation between the Faraday
rotation measures of 1742 radio galaxies at $z > 0.5$ and large-scale structure
at $0.1 < z< 0.5$, as traced by 18 million optical and infrared foreground
galaxies. No significant correlation signal was detected within the uncertainty
limits. We are able to determine model-dependent $3 sigma$ upper limits on the
parallel component of the mean magnetic field strength of filaments in the
intergalactic medium of $sim 30 mathrm{nG}$ for coherence scales between
$1$ and $2.5 mathrm{Mpc}$, corresponding to a mean upper bound RM
enhancement of $sim 3.8 mathrm{rad/m^{2}}$ due to filaments along all
probed sight-lines. These upper bounds are consistent with upper bounds found
previously using other techniques. Our method can be used to further constrain
intergalactic magnetic fields with upcoming future radio polarization surveys.
Large-scale coherent magnetic fields in the intergalactic medium are presumed
to play a key role in the formation and evolution of the cosmic web, and in
large scale feedback mechanisms. However, they are theorized to be extremely
weak, in the nano-Gauss regime. To search for a statistical signature of these
weak magnetic fields we perform a cross-correlation between the Faraday
rotation measures of 1742 radio galaxies at $z > 0.5$ and large-scale structure
at $0.1 < z< 0.5$, as traced by 18 million optical and infrared foreground
galaxies. No significant correlation signal was detected within the uncertainty
limits. We are able to determine model-dependent $3 sigma$ upper limits on the
parallel component of the mean magnetic field strength of filaments in the
intergalactic medium of $sim 30 mathrm{nG}$ for coherence scales between
$1$ and $2.5 mathrm{Mpc}$, corresponding to a mean upper bound RM
enhancement of $sim 3.8 mathrm{rad/m^{2}}$ due to filaments along all
probed sight-lines. These upper bounds are consistent with upper bounds found
previously using other techniques. Our method can be used to further constrain
intergalactic magnetic fields with upcoming future radio polarization surveys.
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