arXiv subjects

Fred J. Jennings

Publications and source records attributed to Fred J. Jennings.

3 recordsLinked to original sources

arXiv2026

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

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.

astro-ph.GA↗

arXiv2026

BlackHoleWeather -- Chaotic cold accretion across the meso-scale: Morphology and thermodynamics

Supermassive black holes (SMBHs) self-regulate galaxies, groups, and clusters, yet the pathway transporting gas from halo scales to sub-pc radii remains debated. In hot stratified atmospheres, subsonic turbulence can trigger nonlinear thermal instability and a multiphase condensation cascade, producing chaotic time-variable BH `weather'. A key missing link is how the meso-scale connects halo rain to nuclear inflow. We study turbulence-driven condensation and chaotic cold accretion (CCA) in a group-scale halo, quantifying how the stirring level shapes multiphase morphology, thermodynamics, and SMBH feeding. We ran 3D hydrodynamic hyper-zoom simulations with a GPU-accelerated code, including cooling and driven subsonic turbulence in a hot intragroup halo. Two endpoint runs bracket weak and strong stirring, capturing distinct BH weather states. In both regimes the atmosphere becomes thermally unstable and develops a multiphase medium spanning 8-10 dex in temperature and density. Strong stirring delays cold gas accretion and sustains an extended filament-rich rain pattern to kpc radii (`stormy' CCA), with broader thermodynamic distributions beyond the nucleus. Weak stirring triggers earlier condensation but yields a more compact rain, with most cold gas confined within 100 pc (`rainy' CCA). At micro-scales the inflow is partly mediated by a clumpy rotating torus. Despite large differences in condensed cold mass, the BH accretion rate is recurrently boosted by up to 100x above the hot-mode Bondi baseline and varies weakly between the weather regimes, indicating that feeding is regulated primarily by how efficiently multiphase structures couple to the central inflow. Modest turbulence changes are sufficient to shift the same hot halo between stormy (extended) and rainy (centralized) BH weather, providing a quantitative multiscale baseline for interpreting multiphase CCA and SMBH feeding.

astro-ph.GA↗

arXiv2024

Hyenas: X-ray Bubbles and Cavities in the Intra-Group Medium

We investigate the role of the Simba feedback model on the structure of the Intra-Group Medium (IGrM) in the new Hyenas suite of cutting-edge cosmological zoom-in simulations. Using 34 high-resolution zooms of halos spanning from $10^{13}-10^{14}$ $M_\odot$ at $z=0.286$, we follow halos for 700 Myr, over several major active galactic nuclei (AGN) jet feedback events. We use the MOXHA package to generate mock Chandra X-ray observations, as well as predictive mocks for the upcoming LEM mission, identifying many feedback-generated features such as cavities, shock-fronts, and hot-spots, closely mimicking real observations. Our sample comprises $105$ snapshots with identified cavities, $50$ with single bubbles and $55$ with two, and spans three orders of magnitude in observed cavity enthalpies, from $10^{41}-10^{44}$ erg/s. Comparing semi-major axis length, midpoint radius, and eccentricity to a matched sample of observations, we find good agreement in cavity dimensions with real catalogues. We estimate cavity power from our mock maps following observational procedures, showing that this is typically more than enough to offset halo cooling, particularly in low-mass halos, where we match the observed excess in energy relative to cooling. Bubble enthalpy as measured with the usual midpoint pressure typically exceeds the energy released by the most recent jet event, hinting that the mechanical work is done predominantly at a lower pressure against the IGrM. We demonstrate for the first time that X-ray cavities are observable in a modern large-scale simulation suite and discuss the use of realistic cavity mock observations as new halo-scale constraints on feedback models in cosmological simulations.

astro-ph.GA↗