Fragmentation of protoplanetary discs around M-dwarfs

Backus, Isaac; Quinn, Thomas

doi:10.1093/mnras/stw1825

Cited by 18 publications

(19 citation statements)

References 57 publications

(107 reference statements)

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“…The vertical gas density distribution is taken to be that for hydrostatic balance of a nonself-gravitating disk. Although this initial state is somewhat out of vertical force balance due to self-gravity, this imbalance is unlikely to be responsible for the strong effects we find associated with large-scale shocks (see also Backus & Quinn 2016).…”

Section: Numberical Simulationmentioning

confidence: 77%

Fragmentation of Kozai–Lidov Disks

Lubow

Martin

2017

ApJL

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We analyze the gravitational instability (GI) of a locally isothermal inclined disk around one component of a binary system. Such a disk can undergo global Kozai-Lidov (KL) cycles if the initial disk tilt is above the critical KL angle (of about 40• ). During these cycles, an initially circular disk exchanges its inclination for eccentricity, and vice versa. Self-gravity may suppress the cycles under some circumstances. However, with hydrodynamic simulations including self-gravity we show that for a sufficiently high initial disk tilts and for certain disk masses, disks can undergo KL oscillations and fragment due to GI, even when the Toomre Q value for an equivalent undisturbed disk is well within the stable regime (Q > 2). We suggest that KL triggered disk fragmentation provides a mechanism for the efficient formation of giant planets in binary systems and may enhance fragmentation of disks in massive black hole binaries.

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Section: Numberical Simulationmentioning

confidence: 77%

Fragmentation of Kozai–Lidov Disks

Lubow

Martin

2017

ApJL

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“…MFM is the only method for which we were able to prove convergence of the critical cooling timescale among the methods explored so far, but even in this case exact convergence requires relaxation of the initial conditions in order to avoid transients that lead to sharp flow velocity gradients and high local vorticity at interface regions. The important role of the initial conditions is supported also by a recent study of Backus & Quinn (2016) with locally isothermal disks using a modern formulation of the SPH hydro force, but still standard artificial viscosity, using the ChaNGa code. It is also in line with previous findings by Paardekooper et al (2011) with the FARGO code.…”

Section: Discussionmentioning

confidence: 92%

Convergence of the Critical Cooling Rate for Protoplanetary Disk Fragmentation Achieved: The Key Role of Numerical Dissipation of Angular Momentum

Deng

Mayer

Meru

2017

ApJ

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We carry out simulations of gravitationally unstable disks using smoothed particle hydrodynamics(SPH) and the novel Lagrangian meshless finite mass (MFM) scheme in the GIZMO code (Hopkins 2015). Our aim is to understand the cause of the non-convergence of the cooling boundary for fragmentation reported in the literature. We run SPH simulations with two different artificial viscosity implementations, and compare them with MFM, which does not employ any artificial viscosity. With MFM we demonstrate convergence of the critical cooling time scale for fragmentation at β crit ≈ 3.. Non-convergence persists in SPH codes, although it is significantly mitigated with schemes having reduced artificial viscosity such as inviscid SPH (ISPH) (Cullen & Dehnen 2010). We show how the non-convergence problem is caused by artificial fragmentation triggered by excessive dissipation of angular momentum in domains with large velocity derivatives. With increased resolution such domains become more prominent. Vorticity lags behind density due to numerical viscous dissipation in these regions, promoting collapse with longer cooling times. Such effect is shown to be dominant over the competing tendency of artificial viscosity to diminish with increasing resolution. When the initial conditions are first relaxed for several orbits, the flow is more regular, with lower shear and vorticity in non-axisymmetric regions, aiding convergence. Yet MFM is the only method that converges exactly. Our findings are of general interest as numerical dissipation via artificial viscosity or advection errors can also occur in grid-based codes. Indeed for the FARGO code values of β crit significantly higher than our converged estimate have been reported in the literature. Finally, we discuss implications for giant planet formation via disk instability.

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“…Cai et al 2008;Meru & Bate 2010;Kratter & Murray-Clay 2011;Rice et al 2011;Hall et al 2016) From Kratter & Lodato (2016) and equations 1 and 2 we do have an anticipated scaling of disc stability with stel-lar mass. However this has not yet been directly confirmed with simulations (Backus & Quinn 2016, model isothermal discs around 0.3 M M stars for discs of radius from 1/3 to 30 AU and for M d /M * from 0.033 to 0.266 and find GI can occur, but do not model how the behaviour is sensitive to stellar mass). An additional issue is that the evolution of a self-gravitating disc becomes increasingly global for discto-star mass ratios above 0.5 .…”

Section: Introductionmentioning

confidence: 83%

Massive discs around low-mass stars

Haworth

Cadman

Meru

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We use a suite of SPH simulations to investigate the susceptibility of protoplanetary discs to the effects of self-gravity as a function of star-disc properties. We also include passive irradiation from the host star using different models for the stellar luminosities. The critical disc-to-star mass ratio for axisymmetry (for which we produce criteria) increases significantly for low-mass stars. This could have important consequences for increasing the potential mass reservoir in a proto Trappist-1 system, since even the efficient Ormel et al. (2017) formation model will be influenced by processes like external photoevaporation, which can rapidly and dramatically deplete the dust reservoir. The aforementioned scaling of the critical M d /M * for axisymmetry occurs in part because the Toomre Q parameter has a linear dependence on surface density (which promotes instability) and only an M 1/2 * dependence on shear (which reduces instability), but also occurs because, for a given M d /M * , the thermal evolution depends on the host star mass. The early phase stellar irradiation of the disc (for which the luminosity is much higher than at the zero age main sequence, particularly at low stellar masses) can also play a key role in significantly reducing the role of self-gravity, meaning that even Solar mass stars could support axisymmetric discs a factor two higher in mass than usually considered possible. We apply our criteria to the DSHARP discs with spirals, finding that self-gravity can explain the observed spirals so long as the discs are optically thick to the host star irradiation.

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Fragmentation of protoplanetary discs around M-dwarfs

Cited by 18 publications

References 57 publications

Fragmentation of Kozai–Lidov Disks

Fragmentation of Kozai–Lidov Disks

Convergence of the Critical Cooling Rate for Protoplanetary Disk Fragmentation Achieved: The Key Role of Numerical Dissipation of Angular Momentum

Massive discs around low-mass stars

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