Velocity dispersions in galaxy clusters

Girardi, M.; Biviano, A.; Giuricin, G.; Mardirossian, F.; Mezzetti, M.

doi:10.1086/172256

Cited by 129 publications

(146 citation statements)

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“…We determined the velocity dispersion for XMMU J1230.3+1339 using the "robust" estimator of Beers et al (1990) and Girardi et al (1993) applied to the 13 secure cluster members 12 in Table 2 and found σ r 658 ± 277 km s −1 (Fig. 5) in good agreement with the classical dispersion measure of Danese et al (1980).…”

Section: Velocity Dispersionsupporting

confidence: 72%

A pan-chromatic view of the galaxy cluster XMMU J1230.3+1339 atz= 0.975

Fassbender

Böhringer

Santos

et al. 2011

A&A

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Context. Observations of the formation and evolution of massive galaxy clusters and their matter components provide crucial constraints on cosmic structure formation, the thermal history of the intracluster medium (ICM), galaxy evolution, transformation processes, and gravitational and hydrodynamic interaction physics of the subcomponents. Aims. We characterize the global multi-wavelength properties of the X-ray selected galaxy cluster XMMU J1230.3+1339 at z = 0.975, a new system discovered within the XMM-Newton Distant Cluster Project (XDCP). We measure and compare various widely used mass proxies and identify multiple cluster-associated components from the inner core region out to the large-scale structure environment.Methods. We present a comprehensive galaxy cluster study based on a joint analysis of X-ray data, optical imaging and spectroscopy observations, weak lensing results, and radio properties for achieving a detailed multi-component view on a system at z ∼ 1. Results. We find an optically very rich and massive system with M 200 (4.2 ± 0.8) × 10 14 M , T X,2500 5.3 +0.7 −0.6 keV, and L bol X,500 (6.5 ± 0.7) × 10 44 erg s −1 . We have identified a central fly-through group close to core passage and find marginally extended 1.4 GHz radio emission possibly associated with the turbulent wake region of the merging event. On the cluster outskirts we see evidence for an on-axis infalling group with a second brightest cluster galaxy (BCG) and indications for an additional off-axis group accretion event. We trace two galaxy filaments beyond the nominal cluster radius and provide a tentative reconstruction of the 3D-accretion geometry of the system. Conclusions. In terms of total mass, ICM structure, optical richness, and the presence of two dominant BCG-type galaxies, the newly confirmed cluster XMMU J1230.3+1339 is likely the progenitor of a system very similar to the local Coma cluster, differing by 7.6 Gyr of structure evolution. This new system is an ideally suited astrophysical model laboratory for in-depth follow-up studies on the aggregation of baryons in the cold and hot phases.

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Section: Velocity Dispersionsupporting

confidence: 72%

A pan-chromatic view of the galaxy cluster XMMU J1230.3+1339 atz= 0.975

Fassbender

Böhringer

Santos

et al. 2011

A&A

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“…look for gaps in the sorted velocity distribution using the gapper technique of Wainer & Thissen (1976) with C = 4 as proposed by Girardi et al (1993); 2. estimate the virial radius and velocity (r v and v v , respectively) from the aperture velocity dispersion (σ ap ) computed with the robust median absolute deviation estimator, using a scaling of σ ap /v v derived for Navarro, Frenk, and White (1996; NFW hereafter) models with velocity anisotropy estimated in Mamon et al (2010); 3. filter the galaxies, keeping those within the estimated virial radius, R < r v , and within 2.7 predicted line-of-sight velocity dispersions for the NFW model with the Mamon et al (2010) velocity anisotropy from the median velocity,…”

Section: Definition Of the Stacksmentioning

confidence: 99%

Structural and dynamical modeling of WINGS clusters

Cava

Biviano

Mamon

et al. 2017

A&A

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Context. We study the distribution of galaxies in nearby clusters to shed light on the evolutionary processes at work within clusters and prepare for a full dynamical analysis to be conducted in forthcoming papers of this series. Aims. We use the Wide-field Nearby Galaxy-clusters Survey (WINGS) database complemented with literature data. We assign galaxy membership to individual clusters, then select a sample of 67 clusters with at least 30 spectroscopic members each. 53 of these clusters do not show evidence of substructures in phase-space, as measured by the Dressler-Shectman test, while 14 do. We estimate the virial radii and circular velocities of the 67 clusters by a variety of proxies (velocity dispersion, X-ray temperature, and richness) and use these estimates to build stack samples from these 53 and 14 clusters, that we call 'Reg' and 'Irr' stacks, respectively. We show that our results are robust with regard to the choice of the virial radii and circular velocities used to scale galaxy radii and velocities in the stacking procedure. We determine the number-density and velocity-dispersion profiles of Elliptical (E), S0, and Spiral+Irregular (S) galaxies in the Reg and Irr samples, separately, and fit models to these profiles. Methods. The number density profiles of E, S0, and S galaxies are adequately described by either a Navarro, Frenk, & White (NFW) or a cored King model, both for the Reg and Irr samples, with a slight preference for the NFW model. The spatial distribution concentration increases from the S to the S0 and to the E populations, both in the Reg and the Irr stacks, reflecting the well-known morphology-radius relation. Reg clusters have a more concentrated spatial distribution of E and S0 galaxies than Irr clusters, while the spatial distributions of S galaxies in Reg and Irr clusters have a similar concentration. We propose a new phenomenological model that provides acceptable fits to the velocity dispersion profile of all our galaxy samples. The velocity dispersion profiles become steeper and with a higher normalization from E to S0 to S galaxies. The S0 velocity dispersion profile is close to that of E galaxies in Reg clusters, and intermediate between those of E and S galaxies in Irr clusters. Results. Our results suggest that S galaxies are a recently accreted cluster population, that take ≤ 3 Gyr to evolve into S0 galaxies after accretion, and in doing so modify their phase-space distribution, approaching that of cluster ellipticals. While in Reg clusters this evolutionary process is mostly completed, it is still ongoing in Irr clusters.

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“…To avoid the inclusion of these interloper galaxies, often methods use a variety of techniques such as iterative clipping (Yahil & Vidal 1977) or the Gapper technique (Beers et al 1990;Girardi et al 1993) to reach convergence on cluster properties. Alternatively, this interloper contamination can be modelled when performing density fitting (e.g., Wojtak et al 2007).…”

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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Velocity dispersions in galaxy clusters

Cited by 129 publications

References 0 publications

A pan-chromatic view of the galaxy cluster XMMU J1230.3+1339 atz= 0.975

A pan-chromatic view of the galaxy cluster XMMU J1230.3+1339 atz= 0.975

Structural and dynamical modeling of WINGS clusters

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

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