Efficient Production of Sound Waves by AGN Jets in the Intracluster Medium. (arXiv:1906.03272v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Bambic_C/0/1/0/all/0/1">Christopher J. Bambic</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reynolds_C/0/1/0/all/0/1">Christopher S. Reynolds</a>
We investigate the interaction between active galactic nuclei (AGN) jets and
the intracluster medium (ICM) of galaxy clusters. Specifically, we study the
efficiency with which jets can drive sound waves into the ICM. Previous works
focused on this issue model the jet-ICM interaction as a spherically symmetric
explosion, finding that <~ 12.5% of the blast energy is converted into sound
waves, even for instantaneous energy injection. We develop a method for
measuring sound wave energy in hydrodynamic simulations and measure the
efficiency of sound wave driving by supersonic jets in a model ICM. Our
axisymmetric fiducial simulations convert >~ 25% of the jet energy into strong,
long-wavelength sound waves which can propagate to large distances. Vigorous
instabilities driven by the jet-ICM interaction generate small-scale sound
waves which constructively interfere, forming powerful large-scale waves. By
scanning a parameter space of opening angles, velocities, and densities, we
study how our results depend on jet properties. High velocity, wide angle jets
produce sound waves most efficiently, yet the acoustic efficiency never exceeds
1/3 of the jet energy — an indication that equipartition may limit the
nonlinear energy conversion process. Our work argues that sound waves may
comprise a significant fraction of the energy budget in cluster AGN feedback
and underscores the importance of properly treating compressive wave
dissipation in the weakly collisional, magnetized ICM.
We investigate the interaction between active galactic nuclei (AGN) jets and
the intracluster medium (ICM) of galaxy clusters. Specifically, we study the
efficiency with which jets can drive sound waves into the ICM. Previous works
focused on this issue model the jet-ICM interaction as a spherically symmetric
explosion, finding that <~ 12.5% of the blast energy is converted into sound
waves, even for instantaneous energy injection. We develop a method for
measuring sound wave energy in hydrodynamic simulations and measure the
efficiency of sound wave driving by supersonic jets in a model ICM. Our
axisymmetric fiducial simulations convert >~ 25% of the jet energy into strong,
long-wavelength sound waves which can propagate to large distances. Vigorous
instabilities driven by the jet-ICM interaction generate small-scale sound
waves which constructively interfere, forming powerful large-scale waves. By
scanning a parameter space of opening angles, velocities, and densities, we
study how our results depend on jet properties. High velocity, wide angle jets
produce sound waves most efficiently, yet the acoustic efficiency never exceeds
1/3 of the jet energy — an indication that equipartition may limit the
nonlinear energy conversion process. Our work argues that sound waves may
comprise a significant fraction of the energy budget in cluster AGN feedback
and underscores the importance of properly treating compressive wave
dissipation in the weakly collisional, magnetized ICM.
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