BlackHoleWeather -- Chaotic cold accretion across the meso-scale: Variability and kinematics

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Main Authors: Barbani, Filippo, Gaspari, Massimo, Piana, Olmo, Cammelli, Vieri, Jennings, Fred J., Brustio, Davide M., Stel, Giovanni, Olivares, Valeria, Maccagni, Filippo M., Fournier, Martin, Tombesi, Francesco, Temi, Pasquale, Fiore, Fabrizio, Serafinelli, Roberto, Danehkar, Ashkbiz
Format: Preprint
Published: 2026
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author Barbani, Filippo
Gaspari, Massimo
Piana, Olmo
Cammelli, Vieri
Jennings, Fred J.
Brustio, Davide M.
Stel, Giovanni
Olivares, Valeria
Maccagni, Filippo M.
Fournier, Martin
Tombesi, Francesco
Temi, Pasquale
Fiore, Fabrizio
Serafinelli, Roberto
Danehkar, Ashkbiz
author_facet Barbani, Filippo
Gaspari, Massimo
Piana, Olmo
Cammelli, Vieri
Jennings, Fred J.
Brustio, Davide M.
Stel, Giovanni
Olivares, Valeria
Maccagni, Filippo M.
Fournier, Martin
Tombesi, Francesco
Temi, Pasquale
Fiore, Fabrizio
Serafinelli, Roberto
Danehkar, Ashkbiz
contents Accretion onto supermassive black holes (SMBHs) in realistic halos is time-variable, governed by turbulence, cooling, and multiphase condensation. In chaotic cold accretion (CCA), clouds and filaments condense out of the hot gas and feed the SMBH stochastically. We investigate how turbulence regulates the variability, radial transport, and kinematics of CCA, focusing on the meso-scale connecting halo rain to inner inflow. We analyse 3D hydrodynamic simulations with a GPU-accelerated code, including cooling and driven subsonic turbulence in a stratified galaxy group, resolving scales from kpc to sub-pc and probing two turbulent weather regimes. In both regimes, SMBH accretion proceeds through CCA, remains super-Bondi, and varies by up to $\sim 2$ dex. The runs diverge mainly at meso-scales: strong stirring sustains fragmented feeding and clear inflow enhancement at 0.1-1 kpc, whereas weaker turbulence yields a smoother central cascade. Yet innermost feeding rates remain similar, implying SMBH accretion is not directly supply-limited by macro-scale weather. Accretion rate distributions peak at low Eddington ratios, indicating maintenance-mode state. Accretion rate power spectra follow a broken power law, with pink noise on long/intermediate timescales and a steeper red-noise tail at high frequencies, consistent with parsec-scale collisional damping. CCA modes are captured by two complementary diagnostics: the $\mathcal{C}$-ratio ($\equiv t_{\rm cool}/t_{\rm eddy}$) $\approx 1$ identifies soft X-ray gas as the gateway of condensation, while the k-plot (line broadening vs. shift) shows that the weather distinction is strongest on meso-scales, where the stormy regime produces broader, overlapping multiphase kinematics than the rainy regime. The meso-scale bridges halo rain and micro-scale CCA feeding, regulating spatial transport, kinematic imprint, and temporal coherence of SMBH growth.
format Preprint
id arxiv_https___arxiv_org_abs_2605_27504
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle BlackHoleWeather -- Chaotic cold accretion across the meso-scale: Variability and kinematics
Barbani, Filippo
Gaspari, Massimo
Piana, Olmo
Cammelli, Vieri
Jennings, Fred J.
Brustio, Davide M.
Stel, Giovanni
Olivares, Valeria
Maccagni, Filippo M.
Fournier, Martin
Tombesi, Francesco
Temi, Pasquale
Fiore, Fabrizio
Serafinelli, Roberto
Danehkar, Ashkbiz
Astrophysics of Galaxies
High Energy Astrophysical Phenomena
Accretion onto supermassive black holes (SMBHs) in realistic halos is time-variable, governed by turbulence, cooling, and multiphase condensation. In chaotic cold accretion (CCA), clouds and filaments condense out of the hot gas and feed the SMBH stochastically. We investigate how turbulence regulates the variability, radial transport, and kinematics of CCA, focusing on the meso-scale connecting halo rain to inner inflow. We analyse 3D hydrodynamic simulations with a GPU-accelerated code, including cooling and driven subsonic turbulence in a stratified galaxy group, resolving scales from kpc to sub-pc and probing two turbulent weather regimes. In both regimes, SMBH accretion proceeds through CCA, remains super-Bondi, and varies by up to $\sim 2$ dex. The runs diverge mainly at meso-scales: strong stirring sustains fragmented feeding and clear inflow enhancement at 0.1-1 kpc, whereas weaker turbulence yields a smoother central cascade. Yet innermost feeding rates remain similar, implying SMBH accretion is not directly supply-limited by macro-scale weather. Accretion rate distributions peak at low Eddington ratios, indicating maintenance-mode state. Accretion rate power spectra follow a broken power law, with pink noise on long/intermediate timescales and a steeper red-noise tail at high frequencies, consistent with parsec-scale collisional damping. CCA modes are captured by two complementary diagnostics: the $\mathcal{C}$-ratio ($\equiv t_{\rm cool}/t_{\rm eddy}$) $\approx 1$ identifies soft X-ray gas as the gateway of condensation, while the k-plot (line broadening vs. shift) shows that the weather distinction is strongest on meso-scales, where the stormy regime produces broader, overlapping multiphase kinematics than the rainy regime. The meso-scale bridges halo rain and micro-scale CCA feeding, regulating spatial transport, kinematic imprint, and temporal coherence of SMBH growth.
title BlackHoleWeather -- Chaotic cold accretion across the meso-scale: Variability and kinematics
topic Astrophysics of Galaxies
High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2605.27504