TY - JOUR
T1 - 3D Radiation Hydrodynamic Simulations of Gravitational Instability in AGN Accretion Disks
T2 - Effects of Radiation Pressure
AU - Chen, Yi Xian
AU - Jiang, Yan Fei
AU - Goodman, Jeremy
AU - Ostriker, Eve C.
N1 - Funding Information:
Y.X.C. thanks Wenrui Xu, Chang-Goo Kim, Alwin Mao, Douglas Lin, Eliot Quataert, Xue-Ning Bai, Jane Dai, Kaitlin Kratter, Minghao Guo for helpful discussions. We also acknowledge computational resources provided by the high-performance computer center at Princeton University, which is jointly supported by the Princeton Institute for Computational Science and Engineering (PICSciE) and the Princeton University Office of Information Technology. The work of ECO is supported by grant 510940 from the Simons Foundation. The Center for Computational Astrophysics at the Flatiron Institute is supported by the Simons Foundation.
Publisher Copyright:
© 2023. The Author(s). Published by the American Astronomical Society.
PY - 2023/5/1
Y1 - 2023/5/1
N2 - We perform 3D radiation hydrodynamic local shearing-box simulations to study the outcome of gravitational instability (GI) in optically thick active galactic nuclei (AGNs) accretion disks. GI develops when the Toomre parameter Q T ≲ 1, and may lead to turbulent heating that balances radiative cooling. However, when radiative cooling is too efficient, the disk may undergo runaway gravitational fragmentation. In the fully gas-pressure-dominated case, we confirm the classical result that such a thermal balance holds when the Shakura-Sunyaev viscosity parameter (α) due to the gravitationally driven turbulence is ≲0.2, corresponding to dimensionless cooling times Ωt cool ≳ 5. As the fraction of support by radiation pressure increases, the disk becomes more prone to fragmentation, with a reduced (increased) critical value of α (Ωt cool). The effect is already significant when the radiation pressure exceeds 10% of the gas pressure, while fully radiation-pressure-dominated disks fragment at t cool ≲ 50 Ω−1. The latter translates to a maximum turbulence level α ≲ 0.02, comparable to that generated by magnetorotational instability. Our results suggest that gravitationally unstable (Q T ∼ 1) outer regions of AGN disks with significant radiation pressure (likely for high/near-Eddington accretion rates) should always fragment into stars, and perhaps black holes.
AB - We perform 3D radiation hydrodynamic local shearing-box simulations to study the outcome of gravitational instability (GI) in optically thick active galactic nuclei (AGNs) accretion disks. GI develops when the Toomre parameter Q T ≲ 1, and may lead to turbulent heating that balances radiative cooling. However, when radiative cooling is too efficient, the disk may undergo runaway gravitational fragmentation. In the fully gas-pressure-dominated case, we confirm the classical result that such a thermal balance holds when the Shakura-Sunyaev viscosity parameter (α) due to the gravitationally driven turbulence is ≲0.2, corresponding to dimensionless cooling times Ωt cool ≳ 5. As the fraction of support by radiation pressure increases, the disk becomes more prone to fragmentation, with a reduced (increased) critical value of α (Ωt cool). The effect is already significant when the radiation pressure exceeds 10% of the gas pressure, while fully radiation-pressure-dominated disks fragment at t cool ≲ 50 Ω−1. The latter translates to a maximum turbulence level α ≲ 0.02, comparable to that generated by magnetorotational instability. Our results suggest that gravitationally unstable (Q T ∼ 1) outer regions of AGN disks with significant radiation pressure (likely for high/near-Eddington accretion rates) should always fragment into stars, and perhaps black holes.
UR - http://www.scopus.com/inward/record.url?scp=85159822158&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85159822158&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/acc023
DO - 10.3847/1538-4357/acc023
M3 - Article
AN - SCOPUS:85159822158
SN - 0004-637X
VL - 948
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 120
ER -