On Escaping a Galaxy Cluster in an Accelerating Universe

Stark, Andrew; Miller, Christopher J.; Gifford, Daniel

doi:10.3847/0004-637x/830/2/109

Cited by 9 publications

(26 citation statements)

References 56 publications

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“…We use M 200 and r 200 from our simulated cluster sample along with the concentration-mass relation from Merten et al (2015) to analytically model the NFW density and potential profiles given each cluster's mass and inferred concentration. The Einasto density profiles are derived by fitting to the analytic NFW density profiles within r 200 (Sereno et al 2016;Stark et al 2016). Finally, we model the anisotropy as a constant inside r 200 with β = 0.15 ± 0.10 (Iannuzzi & Dolag 2012).…”

Section: The Caustic Techniquementioning

confidence: 99%

Stacking Caustic Masses From Galaxy Clusters

Gifford¹,

Kern²,

Miller³

2017

ApJ

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Ongoing and future spectroscopic surveys will measure numerous galaxy redshifts within tens of thousands of galaxy clusters. However, the sampling within these clusters will be low, 15 < N < 50 per cluster. With such data, it will be difficult to achieve accurate and precise mass estimates for individual clusters using phase-space mass estimation techniques. We develop and test a new stacking algorithm based on the caustic technique, which reduces the mass scatter in ln M caustic |M 200 for ensemble clusters from 70% for individual clusters to less than 10% for ensemble clusters with only 15 galaxies per cluster and 100 clusters per ensemble. With > 1000 galaxies per ensemble phase-space, the escape-velocity edge becomes readily identifiable and the presence of interloping galaxies is minimized. We develop and test an algorithm to trace the projected phase-space surface directly, which results in minimally biased dynamical mass estimates. We then quantify how binning and sampling affect the phase-space-based mass estimates when using an observational proxy that incorporates realistic mass scatter, like richness, and find the added uncertainty in the binning procedure has minimal influence on the resulting bias and scatter of the stacked mass estimates.

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Section: The Caustic Techniquementioning

confidence: 99%

Stacking Caustic Masses From Galaxy Clusters

Gifford¹,

Kern²,

Miller³

2017

ApJ

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“…More specifically, the cosmological dependence in the escape velocity profile in Refs. [9,10,14] comes in through the "equivalence radius." In an accelerating universe, the radius out to which one has escaped a cluster's potential is a function of cosmology.…”

Section: Theoretical Observablementioning

confidence: 99%

“…Once β for a given cluster is inferred we can then use the function g(β) to project our escape velocity profile (see Refs. [9,11]). In particular this function is defined geometrically and given by,…”

Section: A Cluster Parametersmentioning

confidence: 99%

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Cosmology with galaxy cluster phase spaces

2017

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We present a novel approach to constrain accelerating cosmologies with galaxy cluster phase spaces. With the Fisher matrix formalism we forecast constraints on the cosmological parameters that describe the cosmological expansion history. We find that our probe has the potential of providing constraints comparable to, or even stronger than, those from other cosmological probes. More specifically, with 1000 (100) clusters uniformly distributed in the redshift range 0 ≤ z ≤ 0.8, after applying a conservative 80% mass scatter prior on each cluster and marginalizing over all other parameters, we forecast 1σ constraints on the dark energy equation of state w and matter density parameter ΩM of σw = 0.138(0.431) and σΩ M = 0.007(0.025) in a flat universe. Assuming 40% mass scatter and adding a prior on the Hubble constant we can achieve a constraint on the CPL parametrization of the dark energy equation of state parameters w0 and wa with 100 clusters in the same redshift range: σw 0 = 0.191 and σw a = 2.712. Dropping the assumption of flatness and assuming w = −1 we also attain competitive constraints on the matter and dark energy density parameters: σΩ M = 0.101 and σΩ Λ = 0.197 for 100 clusters uniformly distributed in the range 0 ≤ z ≤ 0.8 after applying a prior on the Hubble constant. We also discuss various observational strategies for tightening constraints in both the near and far future.

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“…For example, to estimate dynamical masses accurately, we have to understand the dynamical state of galaxies around galaxy clusters, taking account of motions of galaxies inside clusters as well as those of infalling galaxies. The caustic model is a method to extract the infall sequence to galaxy clusters based on a spherical collapse model (Diaferio & Geller 1997), which is extended to an expanding Universe in Stark et al (2016). However, there is an ambiguity to define the caustic surface in observations due to the projection effect, which has to be calibrated against N-body simulations.…”

Section: Introductionmentioning

confidence: 99%

Constraining cluster masses from the stacked phase space distribution at large radii

Hamabata

Oguri

Nishimichi

2019

Monthly Notices of the Royal Astronomical Society

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Velocity dispersions have been employed as a method to measure masses of clusters. To complement this conventional method, we explore the possibility of constraining cluster masses from the stacked phase space distribution of galaxies at larger radii, where infall velocities are expected to have a sensitivity to cluster masses. First, we construct a two component model of the three-dimensional phase space distribution of haloes surrounding clusters up to 50 h −1 Mpc from cluster centres based on N-body simulations. We find that the three-dimensional phase space distribution shows a clear cluster mass dependence up to the largest scale examined. We then calculate the probability distribution function of pairwise line-of-sight velocities between clusters and haloes by projecting the three-dimensional phase space distribution along the line-of-sight with the effect of the Hubble flow. We find that this projected phase space distribution, which can directly be compared with observations, shows a complex mass dependence due to the interplay between infall velocities and the Hubble flow. Using this model, we estimate the accuracy of dynamical mass measurements from the projected phase space distribution at the transverse distance from cluster centres larger than 2h −1 Mpc. We estimate that, by using 1.5 × 10 5 spectroscopic galaxies, we can constrain the mean cluster masses with an accuracy of 14.5% if we fully take account of the systematic error coming from the inaccuracy of our model. This can be improved down to 5.7% by improving the accuracy of the model.

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On Escaping a Galaxy Cluster in an Accelerating Universe

Cited by 9 publications

References 56 publications

Stacking Caustic Masses From Galaxy Clusters

Stacking Caustic Masses From Galaxy Clusters

Cosmology with galaxy cluster phase spaces

Constraining cluster masses from the stacked phase space distribution at large radii

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