Ahf: Amiga's Halo Finder

Knollmann, Steffen R.; Knebe, Alexander

doi:10.1088/0067-0049/182/2/608

Cited by 838 publications

(779 citation statements)

References 47 publications

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“…The simulations are performed with PKDGRAV2 (Stadel 2001), applying a standard force softening of 1/50 times the mean particle separation. For the halo finding, we use AHF with particle unbinding and an over-density criterion corresponding to spherical tophat collapse (Gill et al 2004;Knollmann & Knebe 2009). A list summarising the main characteristics of the simulations is given in Table 1.…”

Section: Numerical Simulationsmentioning

confidence: 99%

“…Since standard mergertree codes require the same particle numbers between analysed snapshots, we formally increase the particle number of the LR output by splitting every LR particle into n particles corresponding to the HR particles of the same phase-space volume. This simple trick allows us to use the publicly available code MergerTree (out of the AHF-package, Knollmann & Knebe 2009) to calculate the number of shared particles between all haloes in the LR and HR simulations. This then trivially leads to the merit function of Eq.…”

Section: Removing Artefactsmentioning

confidence: 99%

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Structure formation with suppressed small-scale perturbations

Schneider

2015

Monthly Notices of the Royal Astronomical Society

143

215

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All commonly considered dark matter scenarios are based on hypothetical particles with small but non-zero thermal velocities and tiny interaction cross-sections. A generic consequence of these attributes is the suppression of small-scale matter perturbations either due to free-streaming or due to interactions with the primordial plasma. The suppression scale can vary over many orders of magnitude depending on particle candidate and production mechanism in the early Universe.While nonlinear structure formation has been explored in great detail well above the suppression scale, the range around suppressed perturbations is still poorly understood. In this paper we study structure formation in the regime of suppressed perturbations using both analytical techniques and numerical simulations. We develop simple and theoretically motivated recipes for the halo mass function, the expected number of satellites, and the halo concentrations, which are designed to work for power spectra with suppression at arbitrary scale and of arbitrary shape. As case studies, we explore warm and mixed dark matter scenarios where effects are most distinctive. Additionally, we examine the standard dark matter scenario based on weakly interacting massive particles (WIMP) and compare it to pure cold dark matter with zero primordial temperature. We find that our analytically motivated recipes are in good agreement with simulations for all investigated dark matter scenarios, and we therefore conclude that they can be used for generic cases with arbitrarily suppressed small-scale perturbations.

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Section: Numerical Simulationsmentioning

confidence: 99%

Section: Removing Artefactsmentioning

confidence: 99%

Structure formation with suppressed small-scale perturbations

Schneider

2015

Monthly Notices of the Royal Astronomical Society

143

215

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“…Instead of reinventing the wheel, we use the AMIGA Halo Finder (AHF) to calculate these halo properties [30,31]. AHF identifies halos by using the spherical overdensity algorithm.…”

Section: Halo Propertiesmentioning

confidence: 99%

The Vainshtein mechanism in the cosmic web

Falck

Koyama

Zhao

et al. 2014

J. Cosmol. Astropart. Phys.

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We investigate the dependence of the Vainshtein screening mechanism on the cosmic web morphology of both dark matter particles and halos as determined by ORIGAMI. Unlike chameleon and symmetron screening, which come into effect in regions of high density, Vainshtein screening instead depends on the dimensionality of the system, and screened bodies can still feel external fields. ORIGAMI is well-suited to this problem because it defines morphologies according to the dimensionality of the collapsing structure and does not depend on a smoothing scale or density threshold parameter. We find that halo particles are screened while filament, wall, and void particles are unscreened, and this is independent of the particle density. However, after separating halos according to their large scale cosmic web environment, we find no difference in the screening properties of halos in filaments versus halos in clusters. We find that the fifth force enhancement of dark matter particles in halos is greatest well outside the virial radius. We confirm the theoretical expectation that even if the internal field is suppressed by the Vainshtein mechanism, the object still feels the fifth force generated by the external fields, by measuring peculiar velocities and velocity dispersions of halos. Finally, we investigate the morphology and gravity model dependence of halo spins, concentrations, and shapes.

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“…The simulation includes all the standard processes of star formation and its associated metal production and feedback using the prescription of Springel & Hernquist (2003), assuming a Salpeter (Salpeter 1955) initial mass function (IMF) between 0.1 − 100M . Bound structures of more than 20 to- tal (Dark Matter, gas and star) particles are recognised as galaxies using the Amiga Halo Finder (AHF; Knollmann & Knebe 2009). Of all these galaxies, we only use "resolved" galaxies that are complete in the halo mass function in all our calculations -these consist of at least 160 (10) gas (star) particles and have a halo mass M h > ∼ 10 9.2 M .…”

Section: The Modelmentioning

confidence: 99%

Clustering and lifetime of Lyman Alpha Emitters in the Epoch of Reionization

Hutter

Dayal

Müller

2015

Monthly Notices of the Royal Astronomical Society

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We calculate Lyman Alpha Emitter (LAE) angular correlation functions (ACFs) at z 6.6 and the fraction of lifetime (for the 100 Myrs preceding z 6.6) galaxies spend as Lyman Break Galaxies (LBGs) or as LBGs with Lyman Alpha (Lyα) emission using a model that combines SPH cosmological simulations (GADGET-2), dust attenuation and a radiative transfer code (pCRASH). The ACFs are a powerful tool that significantly narrows the 3D parameter space allowed by LAE Lyα and UV luminosity functions (LFs) alone. With this work, we simultaneously constrain the escape fraction of ionizing photons f esc = 0.05 − 0.5, the mean fraction of neutral hydrogen in the intergalactic medium (IGM) χ HI < ∼ 0.01 and the dust-dependent ratio of the escape fractions of Lyα and UV continuum photons f α /f c = 0.6 − 1.2. Our results show that reionization has the largest impact on the amplitude of the ACFs, and its imprints are clearly distinguishable from those of f esc and f α /f c . We also show that galaxies with a critical stellar mass of M * = 10 8.5 (10 9.5 )M produce enough luminosity to stay visible as LBGs (LAEs). Finally, the fraction of time during the past 100 Myrs prior to z = 6.6 a galaxy spends as a LBG or as a LBG with Lyα emission increases with the UV magnitude (and the stellar mass M * ): considering observed (dust and IGM attenuated) luminosities, the fraction of time a galaxy spends as a LBG (LAE) increases from 65% to 100% ( 0 − 100%) as M U V decreases from M U V = −18.0 to −23.5 (M * increases from 10 8 − 10 10.5 M ). Thus in our model the brightest (most massive) LBGs most often show Lyα emission.

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Ahf: Amiga's Halo Finder

Cited by 838 publications

References 47 publications

Structure formation with suppressed small-scale perturbations

Structure formation with suppressed small-scale perturbations

The Vainshtein mechanism in the cosmic web

Clustering and lifetime of Lyman Alpha Emitters in the Epoch of Reionization

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