Velocity structure functions in multiphase turbulence: interpreting kinematics of H$α$ filaments in cool core clusters

Rajsekhar Mohapatra; Mrinal Jetti; Prateek Sharma; Christoph Federrath

doi:10.1093/mnras/stab3429

paper

Velocity structure functions in multiphase turbulence: interpreting kinematics of H $α$ filaments in cool core clusters

arXiv:2109.01771 · doi:10.1093/mnras/stab3429

Abstract

The central regions of cool-core galaxy clusters harbour multiphase gas, with gas temperatures ranging from $10$ $K$ -- $1 0^{7}$ $K$ . Feedback from active galactic nuclei (AGNs) jets prevents the gas from undergoing a catastrophic cooling flow. However, the exact mechanism of this feedback energy input is unknown, mainly due to the lack of velocity measurements of the hot phase gas. However, recent observations have measured the velocity structure functions ( $VSF$ s) of the cooler molecular ( $\sim 10$ $K$ ) and H $α$ filaments ( $\sim 1 0^{4}$ $K$ ) and used them to indirectly estimate the motions of the hot phase. In the first part of this study, we conduct high-resolution ( $38 4^{3}$ -- $153 6^{3}$ resolution elements) simulations of homogeneous isotropic subsonic turbulence, without radiative cooling. We analyse the second-order velocity structure functions ( $VSF_{2}$ ) in these simulations and study the effects of varying spatial resolution, the introduction of magnetic fields, and the effect of projection along the line of sight (LOS) on it. In the second part of the study, we analyse high-resolution ( $76 8^{3}$ resolution elements) idealised simulations of multiphase turbulence in the intracluster medium (ICM) from Mohapatra et al 2021. We compare the $VSF_{2}$ for both the hot ( $T \sim 1 0^{7}$ $K$ ) and cold ( $T \sim 1 0^{4}$ $K$ ) phases and find that their amplitude depends on the density contrast between the phases. They have similar scaling with separation, but introducing magnetic fields steepens the $VSF_{2}$ of only the cold phase. We also find that projection along the LOS steepens the $VSF_{2}$ for the hot phase and mostly flattens it for the cold phase.

17 pages, 11 figures, simulation movies at this youtube playlist: https://www.youtube.com/watch?v=-_0WIfRL9tI&list=PLuaNgQ1v_KMauk1cTu_ellwe6-pTkABIh. Accepted for publication in MNRAS, comments are welcome. Companion study at arxiv ID 2107.07722

Velocity structure functions in multiphase turbulence: interpreting kinematics of H $α$ filaments in cool core clusters

Abstract

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Velocity structure functions in multiphase turbulence: interpreting kinematics of Hα filaments in cool core clusters

Abstract

References in corpus (30)

Cited by in corpus (27)

Velocity structure functions in multiphase turbulence: interpreting kinematics of H $α$ filaments in cool core clusters