Nonlinear Outcome of Gravitational Instability in Disks with Realistic Cooling

Johnson, Bryan M.; Gammie, Charles F.

doi:10.1086/378392

Cited by 169 publications

(244 citation statements)

References 33 publications

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“…Of course, both a constant cooling timescale and our choice are highly idealized assumptions, and further studies are needed to assess which of the two is more reasonable. In principle, one could follow Johnson & Gammie (2003) and find a relation between cooling time and density, based on some opacity prescription. This would not, in general, give t cool Ω =const.…”

Section: Discussionmentioning

confidence: 99%

Testing the locality of transport in self-gravitating accretion discs

Lodato

Rice

2004

AIP Conference Proceedings

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In this paper, we extend our previous analysis of the transport properties induced by gravitational instabilities in cooling, gaseous accretion discs to the case where the disc mass is comparable to the central object. In order to do so, we have performed global, three-dimensional smoothed particle hydrodynamics simulations of massive discs. These new simulations show a much more complex temporal evolution with respect to the less massive case. Whereas in the low disc mass case a self-regulated, marginally stable state (characterized by an approximately constant radial profile of the stability parameter Q) is easily established, in the high disc mass case we observe the development of an initial transient and subsequent settling down in a self-regulated state in some simulations, or a series or recurrent spiral episodes, with low azimuthal wave number m, in others. Accretion in this last case can therefore be a highly variable process. On the other hand, we find that the secular evolution of the disc is relatively slow. In fact, the time-average of the stress induced by selfgravity results in accretion time-scales much longer than the dynamical timescale, in contrast with previous isothermal simulations of massive accretion discs. We have also compared the resulting stress tensor with the expectations based on a local theory of transport, finding no significant evidence for global wave energy transport.

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Section: Discussionmentioning

confidence: 99%

Testing the locality of transport in self-gravitating accretion discs

Lodato

Rice

2004

AIP Conference Proceedings

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“…The radiative cooling Λ in Eq. (2) is determined using the diffusion approximation of the vertical radiation transport in a one-zone model of the vertical disk structure (Johnson & Gammie 2003)…”

Section: Model Descriptionmentioning

confidence: 99%

The effect of external environment on the evolution of protostellar disks

Vorobyov

Lin

Guêdel

2014

A&A

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Aims. Using numerical hydrodynamics simulations, we studied the gravitational collapse of prestellar cores of subsolar mass embedded into a low-density external environment. Methods. Four models with different magnitude and direction of rotation of the external environment with respect to the central core were studied and compared with an isolated model. Results. We found that the infall of matter from the external environment can significantly alter the disk properties as compared to those seen in the isolated model. Depending on the magnitude and direction of rotation of the external environment, a variety of disks can form including compact (≤200 AU) ones shrinking in size owing to infall of external matter with low angular momentum, as well as extended disks forming from infall of external matter with high angular momentum. The former are usually stable against gravitational fragmentation, while the latter are prone to fragmentation and formation of stellar systems with substellar/very-low-mass companions. In the case of a counter-rotating external environment, very compact (<5 AU) and short-lived ( < ∼ a few 10 5 yr) disks can form when infalling material has low angular momentum. The most interesting case is found for the infall of counter-rotating external material with high angular momentum, leading to the formation of counter-rotating inner and outer disks separated by a deep gap at a few tens AU. The gap migrates inward owing to accretion of the inner disk onto the protostar, turns into a central hole, and finally disappears, giving way to the outer strongly gravitationally unstable disk. This model may lead to the emergence of a transient stellar system with planetary/substellar components counter-rotating with respect to that of the star.

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“…Johnson & Gammie 2003). The cooling rateu of the emission is given by dividing F by the surface area of the annulus, and we find the cooling time t cool with (red) and retrograde (blue) mid m simulations.…”

Section: Coolingmentioning

confidence: 71%

Misaligned accretion on to supermassive black hole binaries

Dunhill

Alexander

Nixon

et al. 2014

Monthly Notices of the Royal Astronomical Society

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We present the results of high-resolution numerical simulations of gas clouds falling onto binary supermassive black holes to form circumbinary accretion discs, with both prograde and retrograde cloud orbits. We explore a range of clouds masses and cooling rates. We find that for low mass discs that cool fast enough to fragment, prograde discs are significantly shorter-lived than similar discs orbiting retrograde with respect to the binary. For fragmenting discs of all masses, we also find that prograde discs fragment across a narrower radial region. If the cooling is slow enough that the disc enters a self-regulating gravitoturbulent regime, we find that alignment between the disc and binary planes occurs on a timescale primarily dictated by the disc thickness. We estimate realistic cooling times for such discs, and find that in the majority of cases we expect fragmentation to occur. The longer lifetime of lowmass fragmenting retrograde discs allows them to drive significant binary evolution, and may provide a mechanism for solving the 'last parsec problem'.

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Nonlinear Outcome of Gravitational Instability in Disks with Realistic Cooling

Cited by 169 publications

References 33 publications

Testing the locality of transport in self-gravitating accretion discs

Testing the locality of transport in self-gravitating accretion discs

The effect of external environment on the evolution of protostellar disks

Misaligned accretion on to supermassive black hole binaries

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