<i>N</i>-body simulations of dark matter with frequent self-interactions

Fischer, M.; Brüggen, M.; Schmidt-Hoberg, Kai; Dolag, K.; Kahlhoefer, Felix; Ragagnin, Antonio; Robertson, Andrew

doi:10.1093/mnras/stab1198

Cited by 22 publications

(40 citation statements)

References 69 publications

(73 reference statements)

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“…Kim et al (2017) have performed a parameter study of equal-mass mergers that demonstrated that offsets between DM and galaxies can arise from rare self-interactions. Building on this, Fischer et al (2021) showed that even larger offsets arise when fSIDM is considered, as expected by Kahlhoefer et al (2014). Unequal-mass mergers are interesting since they occur much more frequently than equal-mass mergers.…”

Section: Introductionmentioning

confidence: 63%

“…For our simulations we use the cosmological 𝑁-body code -3, which is a successor of -2 . For rare and frequent self-interactions we are using the implementation described in Fischer et al (2021). This means that for the rare self-interactions a similar scheme to the one introduced by Rocha et al ( 2013) is used and the scheme for frequent self-interactions is based on an effective description employing a drag force (Kahlhoefer et al 2014) and was introduced in Fischer et al (2021).…”

Section: Simulation Code and Implementation Of Self-interactionsmentioning

confidence: 99%

“…For rare and frequent self-interactions we are using the implementation described in Fischer et al (2021). This means that for the rare self-interactions a similar scheme to the one introduced by Rocha et al ( 2013) is used and the scheme for frequent self-interactions is based on an effective description employing a drag force (Kahlhoefer et al 2014) and was introduced in Fischer et al (2021). In addition to the existing implementation, we added a time-step criterion and slightly modified the implementation of rSIDM as described below.…”

Section: Simulation Code and Implementation Of Self-interactionsmentioning

confidence: 99%

“…For both rare and frequent self-interactions we implemented a timestep criterion that limits the maximum allowed time-step for each particle. In this context, our explanation about the time-step scaling for fSIDM in (Fischer et al 2021, section 2.4) might be of interest.…”

Section: Time-step Criterion For Self-interactionsmentioning

confidence: 99%

“…Nevertheless, these studies have been limited to large-angle scattering. Meanwhile, frequent self-interactions have only very recently been implemented in 𝑁-body simulations based on an effective drag force (Fischer et al 2021), which is more generally applicable than the description in terms of a heat conduction approach (Kummer et al 2019). Kim et al (2017) have performed a parameter study of equal-mass mergers that demonstrated that offsets between DM and galaxies can arise from rare self-interactions.…”

Section: Introductionmentioning

confidence: 99%

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Unequal-mass mergers of dark matter haloes with rare and frequent self-interactions

Fischer

Brüggen

Schmidt-Hoberg

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Dark matter self-interactions have been proposed to solve problems on small length scales within the standard cold dark matter cosmology. Here we investigate the effects of dark matter self-interactions in merging systems of galaxies and galaxy clusters with equal and unequal mass ratios. We perform N-body dark matter-only simulations of idealised setups to study the effects of dark matter self-interactions that are elastic and velocity-independent. We go beyond the commonly adopted assumption of large-angle (rare) dark matter scatterings, paying attention to the impact of small-angle (frequent) scatterings on astrophysical observables and related quantities. Specifically, we focus on dark matter-galaxy offsets, galaxy-galaxy distances, halo shapes, morphology and the phase-space distribution. Moreover, we compare two methods to identify peaks: one based on the gravitational potential and one based on isodensity contours. We find that the results are sensitive to the peak finding method, which poses a challenge for the analysis of merging systems in simulations and observations, especially for minor mergers. Large dark matter-galaxy offsets can occur in minor mergers, especially with frequent self-interactions. The subhalo tends to dissolve quickly for these cases. While clusters in late merger phases lead to potentially large differences between rare and frequent scatterings, we believe that these differences are non-trivial to extract from observations. We therefore study the galaxy/star populations which remain distinct even after the dark matter haloes have coalesced. We find that these collisionless tracers behave differently for rare and frequent scatterings, potentially giving a handle to learn about the micro-physics of dark matter.

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Section: Introductionmentioning

confidence: 63%

Section: Simulation Code and Implementation Of Self-interactionsmentioning

confidence: 99%

Section: Simulation Code and Implementation Of Self-interactionsmentioning

confidence: 99%

Section: Time-step Criterion For Self-interactionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Unequal-mass mergers of dark matter haloes with rare and frequent self-interactions

Fischer

Brüggen

Schmidt-Hoberg

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Dark matter in galaxy clusters: Parametric strong-lensing approach

Limousin

Beauchesne

Jullo

2022

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Context. We present a parametric strong-lensing analysis of three massive galaxy clusters for which Hubble Space Telescope imaging is available, as well as spectroscopy of multiply imaged systems and galaxy cluster members. Our aim is to probe the inner shape of dark matter haloes, in particular the existence of a core. We adopted the following working hypothesis: any group-or cluster-scale dark matter clump introduced in the modelling should be associated with a luminous counterpart. We also adopted some additional well-motivated priors in the analysis, even when this degraded the quality of the fit, quantified using the root mean square between the observed and model-generated images. In particular, in order to alleviate the degeneracy between the smooth underlying component and the galaxy-scale perturbers, we used the results from previous spectroscopic campaigns, which allowed us to fix the mass of the galaxy-scale component. In the unimodal galaxy cluster AS 1063, a core mass model is favoured over a non-core mass model, and this is also the case in the multimodal cluster MACS J0416. In the unimodal cluster MACS J1206, we fail to reproduce the strong-lensing constraints using a parametric approach within the adopted working hypothesis. We then successfully added a mild perturbation in the form of a superposition of B-spline potentials, which allowed us to obtain a decent fit (root mean square = 0.5 ′′ ), and finally find that a core mass model is favoured. Overall, our analysis suggest evidence for core cluster-scale dark matter haloes in these three clusters. These findings may be useful for the interpretation within alternative dark matter scenario, such as self-interacting dark matter. We propose a working hypothesis for parametric strong-lensing modelling in which the quest for the best-fit model is balanced by the quest for presenting a physically motivated mass model, in particular by imposing priors. Aims.Methods. Results. Gravitational lensing: strong lensing -Galaxies: cluster -Conclusions.

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Sensitivity of halo shape measurements

Fischer

Valenzuela

2023

A&A

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Shape measurements of galaxies and galaxy clusters are widespread in the analysis of cosmological simulations. But the limitations of those measurements have been poorly investigated. In this Letter, we explain why the quality of the shape measurement does not only depend on the numerical resolution, but also on the density gradient. In particular, this can limit the quality of measurements in the central regions of haloes. We propose a criterion to estimate the sensitivity of the measured shapes based on the density gradient of the halo and to apply it to cosmological simulations of collisionless and self-interacting dark matter. By this, we demonstrate where reliable measurements of the halo shape are possible and how cored density profiles limit their applicability.

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N-body simulations of dark matter with frequent self-interactions

Cited by 22 publications

References 69 publications

Unequal-mass mergers of dark matter haloes with rare and frequent self-interactions

Unequal-mass mergers of dark matter haloes with rare and frequent self-interactions

Dark matter in galaxy clusters: Parametric strong-lensing approach

Sensitivity of halo shape measurements

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