Back to Search
Start Over
3D Radiation Hydrodynamic Simulations of Gravitational Instability in AGN Accretion Disks: Effects of Radiation Pressure
- Source :
- The Astrophysical Journal, Vol 948, Iss 2, p 120 (2023)
- Publication Year :
- 2023
- Publisher :
- IOP Publishing, 2023.
-
Abstract
- 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 Ω t _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 (Ω t _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.
Details
- Language :
- English
- ISSN :
- 15384357
- Volume :
- 948
- Issue :
- 2
- Database :
- Directory of Open Access Journals
- Journal :
- The Astrophysical Journal
- Publication Type :
- Academic Journal
- Accession number :
- edsdoj.573070de2acd453885c7c836793dc6bb
- Document Type :
- article
- Full Text :
- https://doi.org/10.3847/1538-4357/acc023