The mass and anisotropy profiles of galaxy clusters from the projected phase-space density: testing the method on simulated data

Wojtak, Radosław; Łokas, Ewa L.; Mamon, G. A.; Gottlöber, Stefan

doi:10.1111/j.1365-2966.2009.15312.x

Cited by 51 publications

(70 citation statements)

References 57 publications

(98 reference statements)

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“…Observational constraints on the spherical anisotropy β in individual clusters exhibit a huge variety of profiles (Benatov et al 2006;Hwang & Lee 2008;Wojtak & Lokas 2010;Wojtak et al 2009). Some measurements are far outside the margins allowed by the spherically averaged profiles of simulated clusters (see e.g.…”

Section: Observational Constraints On βmentioning

confidence: 99%

“…Lokas 2002;Lokas & Mamon 2003;Wojtak et al 2009;Wolf et al 2010;Mamon et al 2012). Their efficiency, however, critically relies on the quality of the data.…”

Section: Introductionmentioning

confidence: 99%

“…As the matter of fact, most models rely on certain parametrisation of the anisotropy (e.g. Lokas 2002;Mamon et al 2012;Wojtak et al 2009) or incorporate some well-motivated profiles (e.g. Diaferio 1999;Dekel et al 2005) or prior distributions for its parameters (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Orbital anisotropy in cosmological haloes revisited

Wojtak

Gottlöber

Klypin

2013

Monthly Notices of the Royal Astronomical Society

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The velocity anisotropy of particles inside dark matter (DM) haloes is an important physical quantity, which is required for the accurate modelling of mass profiles of galaxies and clusters of galaxies. It is typically measured using the ratio of the radialto-tangential velocity dispersions at a given distance from the halo centre. However, this measure is insufficient to describe the dynamics of realistic haloes, which are not spherical and are typically quite elongated. Studying the velocity distribution in massive DM haloes in cosmological simulations, we find that in the inner parts of the haloes the local velocity ellipsoids are strongly aligned with the major axis of the halo, the alignment being stronger for more relaxed haloes. In the outer regions of the haloes, the alignment becomes gradually weaker and the orientation is more random. These two distinct regions of different degree of the alignment coincide with two characteristic regimes of the DM density profile: a shallow inner cusp and a steep outer profile that are separated by a characteristic radius at which the density declines as ρ ∝ r −2 . This alignment of the local velocity ellipsoids requires reinterpretation of features found in measurements based on the spherically averaged ratio of the radial-to-tangential velocity dispersions. In particular, we show that the velocity distribution in the central halo regions is highly anisotropic. For cluster-size haloes with mass 10 14 − 10 15 h −1 M ⊙ , the velocity anisotropy along the major axis is nearly independent of radius and is equal to β = 1 − σ 2 perp /σ 2 radial ≈ 0.4, which is significantly larger than the previously estimated spherically averaged velocity anisotropy. The alignment of density and velocity anisotropies, and the radial trends may also have some implications for the mass modelling based on kinematical data of such objects as galaxy clusters or dwarf spheroidals, where the orbital anisotropy is a key element in an unbiased mass inference.

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Section: Observational Constraints On βmentioning

confidence: 99%

“…Lokas 2002;Lokas & Mamon 2003;Wojtak et al 2009;Wolf et al 2010;Mamon et al 2012). Their efficiency, however, critically relies on the quality of the data.…”

Section: Introductionmentioning

confidence: 99%

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Orbital anisotropy in cosmological haloes revisited

Wojtak

Gottlöber

Klypin

2013

Monthly Notices of the Royal Astronomical Society

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“…Some methods use the galaxies obtained during the first step of the cluster overdensity search via the FOF algorithm (e.g., Yang et al 2005b;Yang et al 2007;Muñoz-Cuartas & Müller 2012;Tempel et al 2014;Pearson et al in preparation). Other commonly used methods are to select galaxies within a specified region of the colour-magnitude space (e.g., Saro et al 2013) or in projected phase space (e.g., von der Linden et al 2007;Wojtak et al 2009;Mamon et al 2013;Gifford & Miller 2013;Sifón et al 2013;Pearson et al in preparation). Though these techniques generate an impression of which galaxies are associated with a cluster, deducing which galaxies are true members of the cluster is often problematic due to interloping galaxies.…”

Section: Introductionmentioning

confidence: 99%

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

Old

Wojtak

Mamon

et al. 2015

Monthly Notices of the Royal Astronomical Society

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This article is the second in a series in which we perform an extensive comparison of various galaxy-based cluster mass estimation techniques that utilise the positions, velocities and colours of galaxies. Our aim is to quantify the scatter, systematic bias and completeness of cluster masses derived from a diverse set of 25 galaxy-based methods using two contrasting mock galaxy catalogues based on a sophisticated halo occupation model and a semi-analytic model. Analysing 968 clusters, we find a wide range in the RMS errors in log M 200c delivered by the different methods (0.18 to 1.08 dex, i.e., a factor of ∼1.5 to 12), with abundance matching and richness methods providing the best results, irrespective of the input model assumptions. In addition, certain methods produce a significant number of catastrophic cases where the mass is under-or over-estimated by a factor greater than 10. Given the steeply falling high-mass end of the cluster mass function, we recommend that richness or abundance matching-based methods are used in conjunction with these methods as a sanity check for studies selecting high mass clusters. We see a stronger correlation of the recovered to input number of galaxies for both catalogues in comparison with the group/cluster mass, however, this does not guarantee that the correct member galaxies are being selected. We do not observe significantly higher scatter for either mock galaxy catalogues. Our results have implications for cosmological analyses that utilise the masses, richnesses, or abundances of clusters, which have different uncertainties when different methods are used.

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“…The most classical way to characterize the dynamics of clusters is through the analysis of the projected phase space distribution of their member galaxies, e.g. via methods based on the Jeans equation (Binney & Tremaine 1987), such as the dispersion-kurtosis (Łokas & Mamon 2003), distributionfunction (Wojtak et al 2009), and MAMPOSSt (Mamon et al 2013) methods or the caustic method, which is calibrated on numerical simulations (Diaferio & Geller 1997). All these methods assume spherical symmetry and most of them (except the caustic method) also assume dynamical relaxation of the cluster.…”

Section: Introductionmentioning

confidence: 99%

Mass profile and dynamical status of thez~ 0.8 galaxy cluster LCDCS 0504

Guennou¹,

Biviano²,

Adami³

et al. 2014

A&A

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Context. Constraints on the mass distribution in high-redshift clusters of galaxies are currently not very strong. Aims. We aim to constrain the mass profile, M(r), and dynamical status of the z ∼ 0.8 LCDCS 0504 cluster of galaxies that is characterized by prominent giant gravitational arcs near its center. Methods. Our analysis is based on deep X-ray, optical, and infrared imaging as well as optical spectroscopy, collected with various instruments, which we complemented with archival data. We modeled the mass distribution of the cluster with three different mass density profiles, whose parameters were constrained by the strong lensing features of the inner cluster region, by the X-ray emission from the intracluster medium, and by the kinematics of 71 cluster members. Results. We obtain consistent M(r) determinations from three methods based on kinematics (dispersion-kurtosis, caustics, and MAMPOSSt), out to the cluster virial radius, 1.3 Mpc and beyond. The mass profile inferred by the strong lensing analysis in the central cluster region is slightly higher than, but still consistent with, the kinematics estimate. On the other hand, the X-ray based M(r) is significantly lower than the kinematics and strong lensing estimates. Theoretical predictions from ΛCDM cosmology for the concentration-mass relation agree with our observational results, when taking into account the uncertainties in the observational and theoretical estimates. There appears to be a central deficit in the intracluster gas mass fraction compared with nearby clusters. Conclusions. Despite the relaxed appearance of this cluster, the determinations of its mass profile by different probes show substantial discrepancies, the origin of which remains to be determined. The extension of a dynamical analysis similar to that of other clusters of the DAFT/FADA survey with multiwavelength data of sufficient quality will allow shedding light on the possible systematics that affect the determination of mass profiles of high-z clusters, which is possibly related to our incomplete understanding of intracluster baryon physics.

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The mass and anisotropy profiles of galaxy clusters from the projected phase-space density: testing the method on simulated data

Cited by 51 publications

References 57 publications

Orbital anisotropy in cosmological haloes revisited

Orbital anisotropy in cosmological haloes revisited

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

Mass profile and dynamical status of thez~ 0.8 galaxy cluster LCDCS 0504

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