Native synthetic imaging of smoothed particle hydrodynamics density fields using gridless Monte Carlo radiative transfer

Forgan, Duncan; Rice, Ken

doi:10.1111/j.1365-2966.2010.16842.x

Cited by 7 publications

(6 citation statements)

References 47 publications

(61 reference statements)

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“…To compute the distribution of line‐of‐sight peculiar velocity, we ray trace through the SPH simulation using the algorithms described in Altay, Croft & Pelupessy () and Forgan & Rice (). Particles only contribute to the density and velocity fields along the ray if their smoothing volumes intersect it (see Fig.…”

Section: Methodsmentioning

confidence: 99%

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Turbulent linewidths as a diagnostic of self-gravity in protostellar discs

Forgan

Armitage

Simon

2012

Monthly Notices of the Royal Astronomical Society

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We use smoothed particle hydrodynamics simulations of massive protostellar discs to investigate the predicted broadening of molecular lines from discs in which self‐gravity is the dominant source of angular momentum transport. The simulations include radiative transfer, and span a range of disc‐to‐star mass ratios between Md/M* = 0.25 and 1.5. Subtracting off the mean azimuthal flow velocity, we compute the distribution of the in‐plane and perpendicular peculiar velocity due to large‐scale structure and turbulence induced by self‐gravity. For the lower mass discs, we show that the characteristic peculiar velocities scale with the square root of the effective turbulent viscosity parameter, α, as expected from local α‐disc theory. The derived velocities are anisotropic, with substantially larger in‐plane than perpendicular values. As the disc mass is increased, the validity of the α approximation breaks down, and this is accompanied by anomalously large in‐plane broadening. There is also a high variance due to the importance of low‐m spiral modes. For low‐mass discs, the magnitude of in‐plane broadening is, to leading order, equal to the predictions from α disc theory and cannot constrain the source of turbulence. However, combining our results with prior evaluations of turbulent broadening expected in discs where the magnetorotational instability (MRI) is active, we argue that self‐gravity may be distinguishable from the MRI in these systems if it is possible to measure the anisotropy of the peculiar velocity field with disc inclination. Furthermore, for large mass discs, the dominant contribution of large‐scale modes is a distinguishing characteristic of self‐gravitating turbulence versus MRI‐driven turbulence.

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Section: Methodsmentioning

confidence: 99%

“…Particles only contribute to the estimated line‐of‐sight velocity if their smoothing volume intersects the ray. Figure taken from Forgan & Rice ().…”

Section: Methodsmentioning

confidence: 99%

Turbulent linewidths as a diagnostic of self-gravity in protostellar discs

Forgan

Armitage

Simon

2012

Monthly Notices of the Royal Astronomical Society

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“…Episodic accretion maybe due to gravitational instabilities (Vorobyov & Basu 2005;Machida et al 2011;Vorobyov & Basu 2015;Liu et al 2016), thermal instabilities in the inner disc region (Hartmann & Kenyon 1985;Lin et al 1985;Bell & Lin 1994), or due to gravitational interactions in a binary system (Bonnell & Bastien 1992;Forgan & Rice 2010). It has also been suggested that they may be due to the combined effect of gravitational instabilities operating in the outer disc region transferring matter inwards and the magneto-rotational instability (MRI) operating episodically in the inner disc region delivering matter onto the young protostar (Armitage et al 2001;Zhu et al 2007Zhu et al , 2009aZhu et al ,b, 2010.…”

Section: Introductionmentioning

confidence: 99%

The effect of radiative feedback on disc fragmentation

Mercer

Stamatellos

2016

Mon. Not. R. Astron. Soc.

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Protostellar discs may become massive enough to fragment producing secondary lowmass objects: planets, brown dwarfs and low-mass stars. We study the effect of radiative feedback from such newly-formed secondary objects using radiative hydrodynamic simulations. We compare the results of simulations without any radiative feedback from secondary objects with those where two types of radiative feedback are considered: (i) continuous, and (ii) episodic. We find that: (i) continuous radiative feedback stabilizes the disc and suppresses further fragmentation, reducing the number secondary objects formed; (ii) episodic feedback from secondary objects heats and stabilises the disc when the outburst occurs, but shortly after the outburst stops, the disc becomes unstable and fragments again. However, fewer secondary objects are formed compared to the the case without radiative feedback. We also find that the mass growth of secondary objects is mildly suppressed due to the effect of their radiative feedback. However, their mass growth also depends on where they form in the disc and on their subsequent interactions, such that their final masses are not drastically different from the case without radiative feedback. We find that the masses of secondary objects formed by disc fragmentation are from a few M J to a few 0.1 M . Planets formed by fragmentation tend to be ejected from the disc. We conclude that planetary-mass objects on wide orbits (wide-orbit planets) are unlikely to form by disc fragmentation. Nevertheless, disc fragmentation may be a significant source of free-floating planets and brown dwarfs.

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“…Such radiation-hydrodynamics (RHD) schemes have been successfully implemented for grid-based (Harries 2015;Smith et al 2017) and moving mesh (Vandenbroucke & Wood 2018;Smith et al 2020) hydro codes, but are still under development for Smoothed Particle Hydrodynamics (SPH) codes. This is due to the particle nature of SPH and the fact that, with a few exceptions (Forgan & Rice 2010;Lomax & Whitworth 2016), MCRT algorithms are typically performed on a grid.…”

Section: Introductionmentioning

confidence: 99%

Modelling of ionising feedback with Smoothed Particle Hydrodynamics and Monte Carlo Radiative Transfer on a Voronoi grid

Petkova,

Vandenbroucke,

Bonnell

et al. 2021

Preprint

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The ionising feedback of young massive stars is well known to influence the dynamics of the birth environment and hence plays an important role in regulating the star formation process in molecular clouds. For this reason, modern hydrodynamics codes adopt a variety of techniques accounting for these radiative effects. A key problem hampering these efforts is that the hydrodynamics are often solved using smoothed particle hydrodynamics (SPH), whereas radiative transfer is typically solved on a grid. Here we present a radiation-hydrodynamics (RHD) scheme combining the SPH code P and the Monte Carlo Radiative Transfer (MCRT) code CM I , using the particle distribution to construct a Voronoi grid on which the MCRT is performed. We demonstrate that the scheme successfully reproduces the well-studied problem of D-type H II region expansion in a uniform density medium. Furthermore, we use this simulation setup to study the robustness of the RHD code with varying choice of grid structure, density mapping method, and mass and temporal resolution. To test the scheme under more realistic conditions, we apply it to a simulated star-forming cloud reminiscing those in the Central Molecular Zone of our galaxy, in order to estimate the amount of ionised material that a single source could create. We find that a stellar population of several 10 3 M is needed to noticeably ionise the cloud. Based on our results, we formulate a set of recommendations to guide the numerical setup of future and more complex simulations of star forming clouds.

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Native synthetic imaging of smoothed particle hydrodynamics density fields using gridless Monte Carlo radiative transfer

Cited by 7 publications

References 47 publications

Turbulent linewidths as a diagnostic of self-gravity in protostellar discs

Turbulent linewidths as a diagnostic of self-gravity in protostellar discs

The effect of radiative feedback on disc fragmentation

Modelling of ionising feedback with Smoothed Particle Hydrodynamics and Monte Carlo Radiative Transfer on a Voronoi grid

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