Galaxy Cluster Mass Reconstruction Project – II. Quantifying scatter and bias using contrasting mock catalogues

Old, Lyndsay; Wojtak, Radosław; Mamon, G. A.; Skibba, Ramin; Pearce, Frazer R.; Croton, Darren J.; Bamford, Steven P.; Behroozi, Peter; Carvalho, R. R. de; Muñoz-Cuartas, J. C.; Gifford, Daniel; Gray, Meghan E.; Linden, Anja von der; Merrifield, M. R.; Muldrew, Stuart I.; Müller, V.; Pearson, Richard; Ponman, T. J.; Rozo, Eduardo; Rykoff, E. S.; Saro, A.; Sepp, T.; Sifón, Cristobál; Tempel, Elmo

doi:10.1093/mnras/stv421

Cited by 78 publications

(102 citation statements)

References 86 publications

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“…For this study, we use only results of galaxy-based techniques which were tested on mock clusters from the Semi-Analytic Model (SAM)-based dataset described in Section 2.3, where the dynamical properties of the galaxies are taken directly from the underlying N-body dark matter subhaloes themselves (unlike the HOD2 model used in Old et al 2015).…”

Section: Mass Reconstruction Methodsmentioning

confidence: 99%

“…As described in more detail in Old et al (2015), this galaxy formation model is applied to the merger trees described in Section 2.1. In each tree and at each redshift, virialised dark matter haloes are assumed to attract pristine gas from the surrounding environment, from which galaxies form and evolve.…”

Section: Semi-analytic Modelmentioning

confidence: 99%

“…We utilise part of the Galaxy Cluster Mass Reconstruction Project (GCMRP) dataset, where 25 different galaxy-based mass estimation techniques were tested using two mock galaxy catalogues to deduce how well these methods characterised global cluster properties such as mass (Old et al 2014(Old et al , 2015, and how this mass depends on the accuracy of the selected members (Wojtak et al in prep. ) The article is organised as follows: we describe the mock galaxy catalogue in Section 2, and the mass reconstruction methods applied to this catalogue in Section 3.…”

Section: Introductionmentioning

confidence: 99%

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Galaxy Cluster Mass Reconstruction Project – III. The impact of dynamical substructure on cluster mass estimates

Old

Wojtak

Pearce

et al. 2017

Monthly Notices of the Royal Astronomical Society

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With the advent of wide-field cosmological surveys, we are approaching samples of hundreds of thousands of galaxy clusters. While such large numbers will help reduce statistical uncertainties, the control of systematics in cluster masses becomes ever more crucial. Here we examine the effects of an important source of systematic uncertainty in galaxy-based cluster mass estimation techniques: the presence of significant dynamical substructure. Dynamical substructure manifests as dynamically distinct subgroups in phase-space, indicating an unrelaxed state. This issue affects around a quarter of clusters in a generally selected sample. We employ a set of mock clusters whose masses have been measured homogeneously with commonly-used galaxy-based mass estimation techniques (kinematic, richness, caustic, radial methods). We use these to study how the relation between observationally estimated and true cluster mass depends on the presence of substructure, as identified by various popular diagnostics. We find that the scatter for an ensemble of clusters does not increase dramatically for clusters with dynamical substructure. However, we find a systematic bias for all methods, such that clusters with significant substructure have higher measured masses than their relaxed counterparts. This bias depends on cluster mass: the most massive clusters are largely unaffected by the presence of significant substructure, but masses are significantly overestimated for lower mass clusters, by ∼ 10% at 10 14 and 20% for 10 13.5 . The use of cluster samples with different levels of substructure can therefore bias certain cosmological parameters up to a level comparable to the typical uncertainties in current cosmological studies.

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Section: Mass Reconstruction Methodsmentioning

confidence: 99%

Section: Semi-analytic Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Galaxy Cluster Mass Reconstruction Project – III. The impact of dynamical substructure on cluster mass estimates

Old

Wojtak

Pearce

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…A similar procedure to calculate the dynamical mass of the supercluster was used in Einasto et al (2015). The reliability of group mass estimation method and mass errors were analysed in Old et al (2014Old et al ( , 2015, where various mass estimation methods were tested on mock galaxy catalogues. The method used in this work performs reasonably well without a clear bias between true and estimated masses.…”

Section: Masses Of Superclustersmentioning

confidence: 99%

Sloan Great Wall as a complex of superclusters with collapsing cores

Einasto

Lietzen

Gramann

et al. 2016

A&A

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Context. The formation and evolution of the cosmic web is governed by the gravitational attraction of dark matter and antigravity of dark energy (cosmological constant). In the cosmic web, galaxy superclusters or their high-density cores are the largest objects that may collapse at present or during the future evolution. Aims. We study the dynamical state and possible future evolution of galaxy superclusters from the Sloan Great Wall (SGW), the richest galaxy system in the nearby Universe. Methods. We calculated supercluster masses using dynamical masses of galaxy groups and stellar masses of galaxies. We employed normal mixture modelling to study the structure of rich SGW superclusters and search for components (cores) in superclusters. We analysed the radial mass distribution in the high-density cores of superclusters centred approximately at rich clusters and used the spherical collapse model to study their dynamical state. Results. The lower limit of the total mass of the SGW is approximately M = 2.5 × 10 16 h −1 M . Different mass estimators of superclusters agree well, the main uncertainties in masses of superclusters come from missing groups and clusters. We detected three high-density cores in the richest SGW supercluster (SCl 027) and two in the second richest supercluster (SCl 019). They have masses of 1.2−5.9 × 10 15 h −1 M and sizes of up to ≈60 h −1 Mpc. The high-density cores of superclusters are very elongated, flattened perpendicularly to the line of sight. The comparison of the radial mass distribution in the high-density cores with the predictions of spherical collapse model suggests that their central regions with radii smaller than 8 h −1 Mpc and masses of up to M = 2 × 10 15 h −1 M may be collapsing. Conclusions. The rich SGW superclusters with their high-density cores represent dynamically evolving environments for studies of the properties of galaxies and galaxy systems.

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“…Old et al (2014Old et al ( , 2015 compared several mass estimation methods using simulated mock galaxy catalogues. The compared mass estimation methods can be divided into several classes: abundance matching, richnessbased methods, virial theorem, various phase-space based methods, caustic technique (see Old et al 2014Old et al , 2015, for references and more details about various methods). According to the comparison results the virial theorem based method used in Tempel et al (2014b) produces quite reliable masses with reasonable scatter compared with the true masses of the galaxy groups/clusters.…”

Section: Masses and Mass-to-light Ratiosmentioning

confidence: 99%

Unusual A2142 supercluster with a collapsing core: distribution of light and mass

Einasto

Gramann

Saar

et al. 2015

A&A

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Context. Superclusters of galaxies can be used to test cosmological models of the formation and evolution of the largest structures in the cosmic web, and of galaxy and cluster evolution in superclusters. Aims. We study the distribution, masses, and dynamical properties of galaxy groups in the A2142 supercluster. Methods. We analyse the global luminosity density distribution in the supercluster and divide the supercluster into the high-density core and the low-density outskirts regions. We find galaxy groups and filaments in these regions, calculate their masses and mass-tolight ratios and analyse their dynamical state with 1D and 3D statistics. We use the spherical collapse model to study the dynamical state of the supercluster. Results. In the A2142 supercluster rich groups and clusters lie along an almost straight line forming the 50 h −1 Mpc long main body of the supercluster. The A2142 supercluster has a very high density core surrounded by lower-density outskirts. The total estimated mass of the supercluster is M est = 6.2 × 10 15 M . More than a half of groups with at least ten member galaxies in the supercluster lie in the high-density core of the supercluster, centred at the X-ray cluster A2142. Most of the groups in the core region are multimodal. In the outskirts of the supercluster, the number of groups is larger than in the core, and groups are poorer. The orientation of the axis of the cluster A2142 follows the orientations of its X-ray substructures and radio halo, and is aligned along the supercluster axis. The high-density core of the supercluster with the global density D8 ≥ 17 and perhaps with D8 ≥ 13 may have started to collapse. Conclusions. A2142 supercluster with collapsing core and straight body, is an unusual object among superclusters. In the course of the future evolution, the supercluster may split into several systems.

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Galaxy Cluster Mass Reconstruction Project – II. Quantifying scatter and bias using contrasting mock catalogues

Cited by 78 publications

References 86 publications

Galaxy Cluster Mass Reconstruction Project – III. The impact of dynamical substructure on cluster mass estimates

Galaxy Cluster Mass Reconstruction Project – III. The impact of dynamical substructure on cluster mass estimates

Sloan Great Wall as a complex of superclusters with collapsing cores

Unusual A2142 supercluster with a collapsing core: distribution of light and mass

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