Clumpy Outflows from Super-Eddington Accreting Black Holes. II. Conditions for Clump Formation
Abstract
Active galactic nuclei (AGNs) commonly exhibit ultra-fast outflows (UFOs) with velocities of $0.03−−0.3~c$. Recent high-resolution X-ray observations with XRISM/Resolve suggest that UFOs may have a clumpy structure. However, the formation and evolution of these clumpy outflows remain poorly understood. In the first paper of this series, we investigated the formation of clumpy outflows using numerical simulations and find that sufficiently high spatial resolution is required to reproduce clumpy structures numerically. In this second paper, we perform a series of numerical experiments to identify the key physical processes governing clump formation. We find that spatial fluctuations of physical quantities at the disk surface are essential for the formation of clumpy outflows, whereas spatial and temporal fluctuations at the inner boundary have only a minor effect. Furthermore, density structure-function analysis suggests that the high-density regions have an elongated morphology with characteristic transverse widths of several tens of Rg, possibly produced by radiation Rayleigh--Taylor instability. A more comprehensive investigation of the instability in general-relativistic radiation magnetohydrodynamic simulations, where accretion disk structures emerge self-consistently, is expected to provide deeper insights into the physical origin of clumpy outflows.
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BibTeX
@misc{hu2026clumpy,
title = {{Clumpy Outflows from Super-Eddington Accreting Black Holes. II. Conditions for Clump Formation}},
author = {Haojie Hu and Yuta Asahina and Shogo Yoshioka and Hiroyuki R. Takahashi and Ken Ohsuga},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.24660},
eprint = {2610.24660},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.24660},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Clumpy Outflows from Super-Eddington Accreting Black Holes. II. Conditions for Clump Formation
AU - Haojie Hu
AU - Yuta Asahina
AU - Shogo Yoshioka
AU - Hiroyuki R. Takahashi
AU - Ken Ohsuga
PY - 2026
DA - 2026/10/17
PB - arXiv
DO - 10.48550/arxiv.2610.24660
UR - https://arxiv.org/abs/2610.24660
AB - Active galactic nuclei (AGNs) commonly exhibit ultra-fast outflows (UFOs) with velocities of $0.03−−0.3~c$. Recent high-resolution X-ray observations with XRISM/Resolve suggest that UFOs may have a clumpy structure. However, the formation and evolution of these clumpy outflows remain poorly understood. In the first paper of this series, we investigated the formation of clumpy outflows using numerical simulations and find that sufficiently high spatial resolution is required to reproduce clumpy structures numerically. In this second paper, we perform a series of numerical experiments to identify the key physical processes governing clump formation. We find that spatial fluctuations of physical quantities at the disk surface are essential for the formation of clumpy outflows, whereas spatial and temporal fluctuations at the inner boundary have only a minor effect. Furthermore, density structure-function analysis suggests that the high-density regions have an elongated morphology with characteristic transverse widths of several tens of R_g, possibly produced by radiation Rayleigh--Taylor instability. A more comprehensive investigation of the instability in general-relativistic radiation magnetohydrodynamic simulations, where accretion disk structures emerge self-consistently, is expected to provide deeper insights into the physical origin of clumpy outflows.
ER -