<scp>Sphenix</scp>: smoothed particle hydrodynamics for the next generation of galaxy formation simulations

Borrow, Josh; Schaller, Matthieu; Bower, Richard; Schaye, Joop

doi:10.1093/mnras/stab3166

Cited by 39 publications

(12 citation statements)

References 77 publications

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“…However, due to a different mach-number those results are not directly comparable. Borrow et al (2022) also present a cloud exposed to a M = 2.7 wind. Compared with us, they find a qualitatively similar evolution with a central cloud holding together and only limited fragmentation or tail formation.…”

Section: Resultsmentioning

confidence: 99%

Sensitivity of non-radiative cloud-wind interactions to the hydrodynamics solver

Braspenning¹,

Schaye²,

Borrow³

et al. 2022

Preprint

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Cloud-wind interactions are common in the interstellar and circumgalactic media. Many studies have used simulations of such interactions to investigate the effect of particular physical processes, but the impact of the choice of hydrodynamics solver has largely been overlooked. Here we study the cloud-wind interaction, also known as the "blob test", using seven different hydrodynamics solvers: Three flavours of SPH, a moving mesh, adaptive mesh refinement and two meshless schemes. The evolution of masses in dense gas and intermediate-temperature gas, as well as the covering fraction of intermediate-temperature gas, are systematically compared for initial density contrasts of 10 and 100, and four numerical resolutions. To isolate the differences due to the hydrodynamics solvers, we use non-radiative simulations without physical conduction. We find large differences between these methods. SPH methods show slower dispersal of the cloud, particularly for the higher density contrast, but faster convergence, especially for the lower density contrast. Predictions for the intermediate-temperature gas differ particularly strongly, also between non-SPH codes, and converge most slowly. We conclude that the hydrodynamical interaction between a dense cloud and a supersonic wind remains an unsolved problem. Studies aiming to understand the physics or observational signatures of cloud-wind interactions should test the robustness of their results by comparing different hydrodynamics solvers.

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Section: Resultsmentioning

confidence: 99%

Sensitivity of non-radiative cloud-wind interactions to the hydrodynamics solver

Braspenning¹,

Schaye²,

Borrow³

et al. 2022

Preprint

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“…SWIFT includes multiple hydrodynamics and gravity schemes, but here we use the SPHENIX SPH scheme, designed with galaxy formation sub-grid models in mind, for the hydrodynamics (Borrow et al 2022). For N-body gravity, we use a solver employing the Fast Multiple Method (Greengard & Rokhlin 1987) with an adaptive opening angle, similar to Dehnen (2014).…”

Section: The Swift Cosmological Simulation Codementioning

confidence: 99%

The impact of stochastic modeling on the predictive power of galaxy formation simulations

Borrow¹,

Schaller²,

Bahé³

et al. 2022

Preprint

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All modern galaxy formation models employ stochastic elements in their sub-grid prescriptions to discretise continuous equations across the time domain. In this paper, we investigate how the stochastic nature of these models, notably star formation, black hole accretion, and their associated feedback, that act on small (< kpc) scales, can back-react on macroscopic galaxy properties (e.g. stellar mass and size) across long (> Gyr) timescales. We find that the scatter in scaling relations predicted by the EAGLE model implemented in the SWIFT code can be significantly impacted by random variability between re-simulations of the same object, even when galaxies are resolved by tens of thousands of particles. We then illustrate how re-simulations of the same object can be used to better understand the underlying model, by showing how correlations between galaxy stellar mass and black hole mass disappear at the highest black hole masses (M BH > 10 8 M ), indicating that the feedback cycle may be interrupted by external processes. We find that although properties that are collected cumulatively over many objects are relatively robust against random variability (e.g. the median of a scaling relation), the properties of individual galaxies (such as galaxy stellar mass) can vary by up to 25%, even far into the well-resolved regime, driven by bursty physics (black hole feedback) and mergers between galaxies. We suggest that studies of individual objects within cosmological simulations be treated with caution, and that any studies aiming to closely investigate such objects must account for random variability within their results.

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“…This method follows the classical SPH formulation (see e.g. Price 2012 for a review of the algorithm), and it has also been implemented in SWIFT to model the evolution of the gas particles (Borrow et al 2022).…”

Section: Gravothermal Core-collapse In a Cosmological Set-upmentioning

confidence: 99%

TangoSIDM: Tantalizing models of Self-Interacting Dark Matter

Correa,

Schaller,

Ploeckinger

et al. 2022

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We introduce the TangoSIDM project, a suite of cosmological simulations of structure formation in a Λ-Self-Interacting Dark Matter (SIDM) universe. TangoSIDM explores the impact of large dark matter (DM) scattering cross sections over dwarf galaxy scales. Motivated by DM interactions that follow a Yukawa potential, the cross section per unit mass, 𝜎/𝑚 𝜒 , assumes a velocity dependent form that avoids violations of current constraints on large scales. We demonstrate that our implementation accurately models not only core formation in haloes, but also gravothermal core collapse. For central haloes in cosmological volumes, frequent DM particle collisions isotropise the particles orbit, making them largely spherical. We show that the velocity-dependent 𝜎/𝑚 𝜒 models produce a large diversity in the circular velocities of satellites haloes, with the spread in velocities increasing as the cross sections reach 20, 60 and 100 cm 2 /g in 10 9 M haloes. The large variation in the haloes internal structure is driven by DM particles interactions, causing in some haloes the formation of extended cores, whereas in others gravothermal core collapse. We conclude that the SIDM models from the Tango project offer a promising explanation for the diversity in the density and velocity profiles of observed dwarf galaxies.

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Sphenix: smoothed particle hydrodynamics for the next generation of galaxy formation simulations

Cited by 39 publications

References 77 publications

Sensitivity of non-radiative cloud-wind interactions to the hydrodynamics solver

Sensitivity of non-radiative cloud-wind interactions to the hydrodynamics solver

The impact of stochastic modeling on the predictive power of galaxy formation simulations

TangoSIDM: Tantalizing models of Self-Interacting Dark Matter

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