A Parameter Space Exploration of Galaxy Cluster Mergers II: Effects of Magnetic Fields. (arXiv:1904.10024v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Brzycki_B/0/1/0/all/0/1">Bryan Brzycki</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+ZuHone_J/0/1/0/all/0/1">John ZuHone</a>
The hot intracluster plasma in clusters of galaxies is weakly magnetized.
Mergers between clusters produce gas compression and motions which can increase
the magnetic field strength. In this work, we perform high-resolution
non-radiative magnetohydrodynamics simulations of binary galaxy cluster mergers
with magnetic fields, to examine the effects of these motions on the magnetic
field configuration and strength, as well as the effect of the field on the gas
itself. Our simulations sample a parameter space of initial mass ratios and
impact parameters. During the first core passage of mergers, the magnetic
energy increases via gas compression. After this, shear flows produce
temporary, Mpc-scale, strong-field “filament” structures. Lastly, magnetic
fields grow stronger by turbulence. Field amplification is most effective for
low mass ratio mergers, but mergers with a large impact parameter can increase
the magnetic energy more via shearing motions. The amplification of the
magnetic field is most effective in between the first two core passages of each
cluster merger. After the second core passage, the magnetic energy in this
region gradually decreases. In general, the transfer of energy from gas motions
to the magnetic field is not significant enough to have a substantial effect on
gas mixing and the subsequent increase in entropy which occurs in cluster cores
as a result. In the absence of radiative cooling, this results in an overall
decrease of the magnetic field strength in cluster cores. In these regions, the
final magnetic field is isotropic, while it can be significantly tangential at
larger radii.
The hot intracluster plasma in clusters of galaxies is weakly magnetized.
Mergers between clusters produce gas compression and motions which can increase
the magnetic field strength. In this work, we perform high-resolution
non-radiative magnetohydrodynamics simulations of binary galaxy cluster mergers
with magnetic fields, to examine the effects of these motions on the magnetic
field configuration and strength, as well as the effect of the field on the gas
itself. Our simulations sample a parameter space of initial mass ratios and
impact parameters. During the first core passage of mergers, the magnetic
energy increases via gas compression. After this, shear flows produce
temporary, Mpc-scale, strong-field “filament” structures. Lastly, magnetic
fields grow stronger by turbulence. Field amplification is most effective for
low mass ratio mergers, but mergers with a large impact parameter can increase
the magnetic energy more via shearing motions. The amplification of the
magnetic field is most effective in between the first two core passages of each
cluster merger. After the second core passage, the magnetic energy in this
region gradually decreases. In general, the transfer of energy from gas motions
to the magnetic field is not significant enough to have a substantial effect on
gas mixing and the subsequent increase in entropy which occurs in cluster cores
as a result. In the absence of radiative cooling, this results in an overall
decrease of the magnetic field strength in cluster cores. In these regions, the
final magnetic field is isotropic, while it can be significantly tangential at
larger radii.
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