SPIDER – IX. Classifying galaxy groups according to their velocity distribution

Ribeiro, André; Carvalho, R. R. de; Trevisan, M.; Capelato, H. V.; Barbera, F. La; Lopes, P. A. A.; Schilling, Ana Cristina

doi:10.1093/mnras/stt1071

Cited by 42 publications

(66 citation statements)

References 79 publications

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“…The AD test has become a relatively common tool used to identify unrelaxed systems from large redshift surveys (e.g. Hou et al 2009;Ribeiro et al 2010;Martínez & Zandivarez 2012;Hou et al 2013;Ribeiro et al 2013;Roberts & Parker 2017), though its efficacy has only been tested in detail using Monte Carlo simulations sampling from idealized parent distributions (both Gaussian and non-Gaussian, Hou et al 2009;Ribeiro et al 2013). These tests have provided useful insight into the strengths and limitations of the AD test, but it is also important to test this technique in a more physical setting.…”

Section: The Anderson-darling Test As a Relaxation Proxymentioning

confidence: 99%

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Connecting optical and X-ray tracers of galaxy cluster relaxation

Roberts

Parker

Hlavacek-Larrondo

2018

Monthly Notices of the Royal Astronomical Society

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Substantial effort has been devoted in determining the ideal proxy for quantifying the morphology of the hot intracluster medium in clusters of galaxies. These proxies, based on X-ray emission, typically require expensive, high-quality X-ray observations making them difficult to apply to large surveys of groups and clusters. Here, we compare optical relaxation proxies with X-ray asymmetries and centroid shifts for a sample of SDSS clusters with high-quality, archival X-ray data from Chandra and XMM-Newton. The three optical relaxation measures considered are: the shape of the member-galaxy projected velocity distribution -measured by the Anderson-Darling (AD) statistic, the stellar mass gap between the most-massive and second-most-massive cluster galaxy, and the offset between the most-massive galaxy (MMG) position and the luminosityweighted cluster centre. The AD statistic and stellar mass gap correlate significantly with X-ray relaxation proxies, with the AD statistic being the stronger correlator. Conversely, we find no evidence for a correlation between X-ray asymmetry or centroid shift and the MMG offset. High-mass clusters (M halo > 10 14.5 M ) in this sample have X-ray asymmetries, centroid shifts, and Anderson-Darling statistics which are systematically larger than for low-mass systems. Finally, considering the dichotomy of Gaussian and non-Gaussian clusters (measured by the AD test), we show that the probability of being a non-Gaussian cluster correlates significantly with X-ray asymmetry but only shows a marginal correlation with centroid shift. These results confirm the shape of the radial velocity distribution as a useful proxy for cluster relaxation, which can then be applied to large redshift surveys lacking extensive X-ray coverage.

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Section: The Anderson-darling Test As a Relaxation Proxymentioning

confidence: 99%

“…Carollo et al 2013) as well as the shape of the satellite velocity distribution (e.g. Ribeiro et al 2010Ribeiro et al , 2013. Previously, we have shown that low-mass galaxies in the inner regions of Gaussian (G) groups have reduced star-forming fractions relative to non-Gaussian (NG) groups (Roberts & Parker 2017).…”

Section: Introductionmentioning

confidence: 96%

Connecting optical and X-ray tracers of galaxy cluster relaxation

Roberts

Parker

Hlavacek-Larrondo

2018

Monthly Notices of the Royal Astronomical Society

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“…To study the structure of superclusters, the input data for Mclust were the coordinates of galaxy groups in superclusters. This package has been used, for example, to search for substructure in galaxy groups and clusters and to refine the group-finding algorithm (Einasto et al 2010(Einasto et al , 2012bRibeiro et al 2013;Tempel et al 2016), to analyse the distribution of different galaxy populations in superclusters (Einasto et al 2011b), and in morphological classification of superclusters (Einasto et al 2011a). …”

Section: Multidimensional Normal Mixture Modellingmentioning

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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“…Higher peculiar velocities of the main galaxies suggest that the main galaxy is located far from the centre, a sign of a possible dynamically young group. Recently Ribeiro et al (2013) used several methods to analyse the structure and dynamical state of galaxy groups and showed that these methods give quite reliable results for groups with more than ten member galaxies. To be on the safe side, we applied 3D normal mixture modelling to groups with N gal ≥ 20, and used groups with N gal ≥ 10 in 1D tests.…”

Section: One-dimensional Testsmentioning

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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SPIDER – IX. Classifying galaxy groups according to their velocity distribution

Cited by 42 publications

References 79 publications

Connecting optical and X-ray tracers of galaxy cluster relaxation

Connecting optical and X-ray tracers of galaxy cluster relaxation

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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