Non-steady heating of cool cores of galaxy clusters by ubiquitous turbulence and AGN. (arXiv:1912.01012v1 [astro-ph.HE])

Non-steady heating of cool cores of galaxy clusters by ubiquitous turbulence and AGN. (arXiv:1912.01012v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Fujita_Y/0/1/0/all/0/1">Yutaka Fujita</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cen_R/0/1/0/all/0/1">Renyue Cen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhuravleva_I/0/1/0/all/0/1">Irina Zhuravleva</a>

Recent cosmological simulations have shown that turbulence should be
generally prevailing in clusters because clusters are continuously growing
through matter accretion. Using hydrodynamic simulations, we study the heating
of cool-core clusters by the ubiquitous turbulence as well as feedback from the
central active galactic nuclei (AGNs). We find that the AGN shows intermittent
activities in the presence of moderate turbulence similar to the one observed
with Hitomi. The cluster core maintains a quasi-equilibrium state for most of
the time because the heating through turbulent diffusion is nearly balanced
with radiative cooling. The balance is gradually lost because of slight
dominance of the radiative cooling, and the AGN is ignited by increased gas
inflow. Finally, when the AGN bursts, the core is heated almost
instantaneously. Thanks to the pre-existing turbulence, the heated gas is
distributed throughout the core without triggering thermal instability and
causing catastrophic cooling, and the core recovers the quasi-equilibrium
state. The AGN bursts can be stronger in lower-mass clusters. Predictions of
our model can be easily checked with future X-ray missions like XRISM and
Athena.

Recent cosmological simulations have shown that turbulence should be
generally prevailing in clusters because clusters are continuously growing
through matter accretion. Using hydrodynamic simulations, we study the heating
of cool-core clusters by the ubiquitous turbulence as well as feedback from the
central active galactic nuclei (AGNs). We find that the AGN shows intermittent
activities in the presence of moderate turbulence similar to the one observed
with Hitomi. The cluster core maintains a quasi-equilibrium state for most of
the time because the heating through turbulent diffusion is nearly balanced
with radiative cooling. The balance is gradually lost because of slight
dominance of the radiative cooling, and the AGN is ignited by increased gas
inflow. Finally, when the AGN bursts, the core is heated almost
instantaneously. Thanks to the pre-existing turbulence, the heated gas is
distributed throughout the core without triggering thermal instability and
causing catastrophic cooling, and the core recovers the quasi-equilibrium
state. The AGN bursts can be stronger in lower-mass clusters. Predictions of
our model can be easily checked with future X-ray missions like XRISM and
Athena.

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