scholarly journals The Role of Discs in the Collapse and Fragmentation of Prestellar Cores

2016 ◽  
Vol 33 ◽  
Author(s):  
O. Lomax ◽  
A. P. Whitworth ◽  
D. A. Hubber
Keyword(s):  
Kinetic Energy ◽  
Smoothed Particle Hydrodynamics ◽  
Low Mass Stars ◽  
Gravitational Instabilities ◽  
Disc Material ◽  
Prestellar Cores ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Low Mass

AbstractDisc fragmentation provides an important mechanism for producing low-mass stars in prestellar cores. Here, we describe smoothed particle hydrodynamics simulations which show how populations of prestellar cores evolve into stars. We find the observed masses and multiplicities of stars can be recovered under certain conditions.First, protostellar feedback from a star must be episodic. The continuous accretion of disc material on to a central protostar results in local temperatures which are too high for disc fragmentation. If, however, the accretion occurs in intense outbursts, separated by a downtime of ~ 104yr, gravitational instabilities can develop and the disc can fragment.Second, a significant amount of the cores’ internal kinetic energy should be in solenoidal turbulent modes. Cores with less than a third of their kinetic energy in solenoidal modes have insufficient angular momentum to form fragmenting discs. In the absence of discs, cores can fragment but results in a top-heavy distribution of masses with very few low-mass objects.

scholarly journals Modelling Planet Formation by Capture-Theory Interactions

2004 ◽  
Vol 202 ◽  
pp. 244-246
Author(s):  
Michael M. Woolfson ◽  
Stephen Oxley
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Planet Formation ◽  
Open Cluster ◽  
Brown Dwarfs ◽  
Low Mass Stars ◽  
Capture Theory ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Solar Type ◽  
Low Mass

Diffuse low-mass stars and brown dwarfs coexist with condensed solar-type stars in the embedded stage of a developing open cluster. It is shown by smoothed-particle-hydrodynamics modelling that interactions between stars and protostars leads to disruption of the protostar to form protoplanets that can then be captured by the star.

scholarly journals Improved δ-SPH Scheme with Automatic and Adaptive Numerical Dissipation

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2858 ◽  
Author(s):  
Abdelkader Krimi ◽  
Luis Ramírez ◽  
Sofiane Khelladi ◽  
Fermín Navarrina ◽  
Michael Deligant ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Smoothed Particle Hydrodynamics ◽  
Numerical Scheme ◽  
Compressible Flows ◽  
Adaptive Method ◽  
Numerical Dissipation ◽  
Numerical Examples ◽  
Weakly Compressible ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

In this work we present a δ-Smoothed Particle Hydrodynamics (SPH) scheme for weakly compressible flows with automatic adaptive numerical dissipation. The resulting scheme is a meshless self-adaptive method, in which the introduced artificial dissipation is designed to increase the dissipation in zones where the flow is under-resolved by the numerical scheme, and to decrease it where dissipation is not required. The accuracy and robustness of the proposed methodology is tested by solving several numerical examples. Using the proposed scheme, we are able to recover the theoretical decay of kinetic energy, even where the flow is under-resolved in very coarse particle discretizations. Moreover, compared with the original δ-SPH scheme, the proposed method reduces the number of problem-dependent parameters.

scholarly journals Planet migration in self-gravitating discs: survival of planets

2020 ◽  
Vol 496 (2) ◽  
pp. 1598-1609 ◽  
Author(s):  
Sahl Rowther ◽  
Farzana Meru
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Three Dimensional ◽  
Cooling Time ◽  
Early Stages ◽  
Simplified Method ◽  
Planet Migration ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Low Mass ◽  
Protoplanetary Discs

ABSTRACT We carry out three-dimensional smoothed particle hydrodynamics simulations to study whether planets can survive in self-gravitating protoplanetary discs. The discs modelled here use a cooling prescription that mimics a real disc, which is only gravitationally unstable in the outer regions. We do this by modelling the cooling using a simplified method such that the cooling time in the outer parts of the disc is shorter than in the inner regions, as expected in real discs. We find that both giant (>MSat) and low-mass (<MNep) planets initially migrate inwards very rapidly, but are able to slow down in the inner gravitationally stable regions of the disc without needing to open up a gap. This is in contrast to previous studies where the cooling was modelled in a more simplified manner where, regardless of mass, the planets were unable to slow down their inward migration. This shows the important effect the thermodynamics has on planet migration. In a broader context, these results show that planets that form in the early stages of the discs’ evolution, when they are still quite massive and self-gravitating, can survive.

scholarly journals Accretion onto Protoplanetary Discs: Implications for Globular Cluster Evolution

2015 ◽  
Vol 12 (S316) ◽  
pp. 334-335
Author(s):  
T. P. G. Wijnen ◽  
O. R. Pols ◽  
F. I. Pelupessy ◽  
S. Portegies Zwart
Keyword(s):  
Globular Clusters ◽  
Mass Star ◽  
Low Mass Stars ◽  
The Past ◽  
Cluster Evolution ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Low Mass ◽  
Gas Accretion ◽  
Classical Picture

AbstractIn the past decade, observational evidence that Globular Clusters (GCs) harbour multiple stellar populations has grown steadily. These observations are hard to reconcile with the classical picture of star formation in GCs, which approximates them as a single generation of stars. Bastian et al. recently suggested an evolutionary scenario in which a second, chemically distinct, population is formed by the accretion of chemically enriched material onto the protoplanetary disc of low-mass stars in the initial GC population. Using assumptions that represent the (dynamical) conditions in a typical GC, we investigate whether a low-mass star surrounded by a protoplanetary disc can accrete sufficient enriched material to account for the observed abundances in ‘second generation’ stars. We compare the outcome of two different smoothed particle hydrodynamics codes and focus on the lifetime and stability of the disc and on the gas accretion rate onto both the star and the disc.

scholarly journals Fragmentation favoured in discs around higher mass stars

2020 ◽  
Vol 492 (4) ◽  
pp. 5041-5051 ◽  
Author(s):  
James Cadman ◽  
Ken Rice ◽  
Cassandra Hall ◽  
Thomas J Haworth ◽  
Beth Biller
Keyword(s):  
Gravitational Instability ◽  
High Mass ◽  
Low Mass Stars ◽  
Star Mass ◽  
Gravitational Instabilities ◽  
Mass Ratios ◽  
Particle Hydrodynamics ◽  
Low Mass ◽  
M Stars ◽  
Self Gravity

ABSTRACT We investigate how a protoplanetary disc’s susceptibility to gravitational instabilities and fragmentation depends on the mass of its host star. We use 1D disc models in conjunction with 3D smoothed particle hydrodynamics simulations to determine the critical disc-to-star mass ratios at which discs become unstable against fragmentation, finding that discs become increasingly prone to the effects of self-gravity as we increase the host star mass. The actual limit for stability is sensitive to the disc temperature, so if the disc is optically thin stellar irradiation can dramatically stabilize discs against gravitational instability. However, even when this is the case we find that discs around 2 M⊙ stars are prone to fragmentation, which will act to produce wide-orbit giant planets and brown dwarfs. The consequences of this work are twofold: that low-mass stars could in principle support high disc-to-star mass ratios, and that higher mass stars have discs that are more prone to fragmentation, which is qualitatively consistent with observations that favour high-mass wide-orbit planets around higher mass stars. We also find that the initial masses of these planets depends on the temperature in the disc at large radii, which itself depends on the level of stellar irradiation.

scholarly journals Massive discs around low-mass stars

2020 ◽  
Vol 494 (3) ◽  
pp. 4130-4148 ◽  
Author(s):  
Thomas J Haworth ◽  
James Cadman ◽  
Farzana Meru ◽  
Cassandra Hall ◽  
Emma Albertini ◽  
...  
Keyword(s):  
Thermal Evolution ◽  
Solar Mass ◽  
Low Mass Stars ◽  
Star Mass ◽  
Smoothed Particle ◽  
Low Mass ◽  
Self Gravity ◽  
Stellar Masses ◽  
Smoothed Particle Hydrodynamic

ABSTRACT We use a suite of smoothed particle hydrodynamic 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. 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 Md/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 Md/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.

scholarly journals Self-gravitating disks in binary systems: an SPH approach

2019 ◽  
Vol 628 ◽  
pp. A82
Author(s):  
L. D. Pinto ◽  
R. Capuzzo-Dolcetta ◽  
G. Magni
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Binary Systems ◽  
Open Clusters ◽  
Star Mass ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Sph Algorithm ◽  
The Stability ◽  
Self Gravity

The study of the stability of massive gaseous disks around a star in a nonisolated context is a difficult task and becomes even more complicated for disks that are hosted by binary systems. The role of self-gravity is thought to be significant when the ratio of the disk-to-star mass is non-negligible. To solve these problems, we implemented, tested, and applied our own smoothed particle hydrodynamics (SPH) algorithm. The code (named GaSPH) passed various quality tests and shows good performances, and it can therefore be reliably applied to the study of disks around stars when self-gravity needs to be accounted for. We here introduce and describe the algorithm, including some performance and stability tests. This paper is the first part of a series of studies in which self-gravitating disks in binary systems are let evolve in larger environments such as open clusters.

scholarly journals Response Analysis of Submerged Floating Tunnel Hit by Submarine Based on Smoothed-Particle Hydrodynamics

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Gang Luo ◽  
Shaokang Pan ◽  
Yulong Zhang ◽  
Liang Chen
Keyword(s):  
Kinetic Energy ◽  
Smoothed Particle Hydrodynamics ◽  
Coupling Method ◽  
Response Analysis ◽  
Initial Kinetic Energy ◽  
Kinematic Parameters ◽  
Particle Hydrodynamics ◽  
Submerged Floating Tunnel ◽  
Smoothed Particle ◽  
The Impact

This paper presents the theoretical investigation on the damage of the submerged floating tunnel (SFT) under extreme loads. Water was modeled by smoothed-particle hydrodynamics (SPH). Anchor cables, SFT, and submarine were modeled by the finite element method (FEM). Penetrating phenomenon in the calculation process was achieved by the penalty function, and the fluid-solid coupling effect was also considered in the simulation. The process of a submarine striking on the SFT was studied based on the commercial software. The relationships between the energy of the water, submarine, and SFT were studied. The structural and human damages were evaluated using the kinematics and kinetic parameters of the SFT according to the relevant criterion. The results indicate that the SPH-FEM coupling method is suitable to investigate the impact of the SFT in the water. The initial kinetic energy of the submarine is mainly converted into kinetic energy of the water and internal energy of the tunnel. The kinematic parameters at the impact point reach a peak value. The kinematic parameters at the anchor cables reach the minimum value, so the anchor cables can inhibit the development of disaster significantly. The SPH-FEM coupling method can be helpful for collision and explosion analysis of the SFT.

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