Moving mesh cosmology: numerical techniques and global statistics

Vogelsberger, Mark; Sijacki, Debora; Keres, Dusan; Springel, Volker; Hernquist, Lars

doi:10.48550/arxiv.1109.1281

Cited by 12 publications

(13 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similar conclusions were reached in a set of companion papers (Sijacki et al 2011;Vogelsberger et al 2011), in which the new code was used in galaxy formation studies to demonstrate its superiority over standard SPH. However, the code is characterized by considerable complexity which makes the use the SPH scheme still appealing and, more generally, it is desirable that simulation results produced with a specific code should be reproduced with a completely independent numerical scheme when complex non-linear phenomena are involved.…”

Section: Introductionsupporting

confidence: 72%

Hydrodynamic capabilities of an SPH code incorporating an artificial conductivity term with a gravity-based signal velocity

Valdarnini

2012

A&A

View full text Add to dashboard Cite

This paper investigates the hydrodynamic performances of an smoothed particle hydrodynamics (SPH) code incorporating an artificial heat conductivity term in which the adopted signal velocity is applicable when gravity is present. To this end, we analyze results from simulations produced using a suite of standard hydrodynamical test problems. In accordance with previous findings, we show that the performances of SPH in describing the development of Kelvin-Helmholtz instabilities depend strongly on both the consistency of the initial condition set-up and the leading error in the momentum equation due to incomplete kernel sampling. In contrast, the presence of artificial conductivity does not significantly affect the results. An error and stability analysis shows that the quartic B-spline kernel (M 5 ) possesses very good stability properties and so we propose its use with a large neighbor number, between ∼50 (2D) to ∼100 (3D), to improve convergence in simulation results without being affected by the so-called clumping instability. Moreover, the results of the Sod shock tube demonstrate that to obtain simulation profiles in accord with the analytic solution, for simulations employing kernels with a non-zero first derivative at the origin, it is necessary to use a much larger number of neighbors than in the case of the M 5 runs. Our SPH simulations of the blob test show that in order to achieve blob disruption it is necessary to include an artificial conductivity term. However, we find that in the regime of strong supersonic flows an appropriate limiting condition, which depends on the Prandtl number, must be imposed on the artificial conductivity SPH coefficients in order to avoid an unphysical amount of heat diffusion. Our results from hydrodynamic simulations that include self-gravity show profiles of hydrodynamic variables that are in much better agreement with those produced using mesh-based codes. In particular, the final levels of core entropies in cosmological simulations of galaxy clusters are consistent with those found using AMR codes. This demonstrates that the proposed diffusion scheme is capable of mimicking the process of entropy mixing that is produced during structure formation because of the diffusion caused by turbulence. Finally, the results of our Rayleigh-Taylor instability test demonstrate that in the regime of very subsonic flows the code still has several difficulties in the treatment of hydrodynamic instabilities. These problems are intrinsic to the way in which standard SPH gradients are calculated and not to the implementation of the artificial conductivity term. To overcome these difficulties, several numerical schemes have been proposed that, if coupled with the SPH implementation presented in this paper, could solve the issues that have recently been addressed in investigating SPH performances to model subsonic turbulence.

show abstract

Section: Introductionsupporting

confidence: 72%

Hydrodynamic capabilities of an SPH code incorporating an artificial conductivity term with a gravity-based signal velocity

Valdarnini

2012

A&A

View full text Add to dashboard Cite

show abstract

“…We note that some recent studies of low-resolution cosmological simulations comparing GADGET and the moving mesh code AREPO (Springel 2010) have highlighted some differences between smoothed particle hydrodynamics and grid methods for some cosmological inflow problems (Vogelsberger et al 2011;Kereš et al 2012;Torrey et al 2011). However, we have also performed idealized simulation comparisons between the individual, high-resolution galaxy models here (as well as galaxy mergers) and found excellent agreement for e.g.…”

Section: The Simulationssupporting

confidence: 62%

Stellar feedback and bulge formation in clumpy discs

Hopkins

Kereš

Murray

et al. 2012

Monthly Notices of the Royal Astronomical Society

Self Cite

150

158

View full text Add to dashboard Cite

We use numerical simulations of isolated galaxies to study the effects of stellar feedback on the formation and evolution of giant star‐forming gas ‘clumps’ in high‐redshift, gas‐rich galaxies. Such galactic discs are unstable to the formation of bound gas‐rich clumps whose properties initially depend only on global disc properties, not the microphysics of feedback. In simulations without stellar feedback, clumps turn an order‐unity fraction of their mass into stars and sink to the centre, forming a large bulge and kicking most of the stars out into a much more extended stellar envelope. By contrast, strong radiative stellar feedback disrupts even the most massive clumps after they turn ∼10–20 per cent of their mass into stars, in a time‐scale of ∼10–100 Myr, ejecting some material into a superwind and recycling the rest of the gas into the diffuse interstellar medium (ISM). This suppresses the bulge formation rate by direct ‘clump coalescence’ by a factor of several. However, the galactic discs do undergo significant internal evolution in the absence of mergers: clumps form and disrupt continuously and torque gas to the galactic centre. The resulting evolution is qualitatively similar to bar/spiral evolution in simulations with a more homogeneous ISM.

show abstract

“…While not quite as highresolution as our "intermediate-scale" re-simulation runs, these provide an important check on the results of the latter and are run self-consistently for 4 × 10 9 yr. We have followed the same procedure on small scales: running 5 "intermediate-scale" simulations (with a range of gas fraction and bulge-to-disk ratio) with > 10 7 gas particles and softening of ∼ 0.3 pc; these extend from scales ∼ 0.3 − 1000 pc and are run for 2 × 10 8 yr. In Hopkins & Quataert (2010a) and Hopkins & Quataert (2011a) we explicitly compare the results of these simulations with those of our "re-simulations" at the dynamic range where they overlap, and find they are very similar (see e. We note that recent studies comparing cosmological simulations done with GADGET and the new moving mesh code AREPO (Springel 2010) have called into question the reliability of smoothed particle hydrodynamics (SPH) for some problems related to galaxy formation in a cosmological context (Vogelsberger et al 2011;Sijacki et al 2011;Keres et al 2011;Bauer & Springel 2011). However, we have also performed idealized simulations of mergers between individual galaxies and found excellent agreement between GADGET and AREPO for e.g.…”

Section: Gasmentioning

confidence: 61%

Why are active galactic nuclei and host galaxies misaligned?

Hopkins

Hernquist

Hayward

et al. 2012

Monthly Notices of the Royal Astronomical Society

Self Cite

View full text Add to dashboard Cite

It is well established observationally that the characteristic angular momentum axis on small scales around active galactic nuclei (AGN), traced by radio jets and the putative torus, is not well correlated with the large‐scale angular momentum axis of the host galaxy. In this paper, we show that such misalignments arise naturally in high‐resolution simulations in which we follow angular momentum transport and inflows from galaxy to sub‐pc scales near AGN, triggered either during galaxy mergers or by instabilities in isolated discs. Sudden misalignments can sometimes be caused by single massive clumps falling into the centre slightly off‐axis, but more generally, they arise even when the gas inflows are smooth and trace only global gravitational instabilities. When several nested, self‐gravitating modes are present, the inner ones can precess and tumble in the potential of the outer modes. Resonant angular momentum exchange can flip or re‐align the spin of an inner mode on a short time‐scale, even without the presence of massive clumps. We therefore do not expect that AGN and their host galaxies will be preferentially aligned, nor should the relative alignment be an indicator of the AGN fuelling mechanism. We discuss implications of this conclusion for AGN feedback and black hole (BH) spin evolution. The misalignments may mean that even BHs accreting from smooth large‐scale discs will not be spun up to maximal rotation and so have more modest radiative efficiencies and inefficient jet formation. Even more random orientations/lower spins are possible if there is further unresolved clumpiness in the gas, and more ordered accretion may occur if the inflow is slower and not self‐gravitating.

show abstract

Moving mesh cosmology: numerical techniques and global statistics

Cited by 12 publications

References 0 publications

Hydrodynamic capabilities of an SPH code incorporating an artificial conductivity term with a gravity-based signal velocity

Hydrodynamic capabilities of an SPH code incorporating an artificial conductivity term with a gravity-based signal velocity

Stellar feedback and bulge formation in clumpy discs

Why are active galactic nuclei and host galaxies misaligned?

Contact Info

Product

Resources

About