On the dynamics of the cores of galaxy clusters

Hartog, R. den; Katgert, P.

doi:10.1093/mnras/279.2.349

Cited by 141 publications

(97 citation statements)

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“…This velocity gradient of ∼ 847 ± 114 km s −1 could indicate some rotation ω around this axis (see Figure 7). It is consistent with typical gradients (240 − 1230 km s −1 ) found in clusters studied by den Hartog & Katgert (1996).…”

Section: Velocity Gradientsupporting

confidence: 91%

Dynamical analysis of the cluster pair: A3407 + A3408

Nascimento

Ribeiro

Trevisan

et al. 2016

Mon. Not. R. Astron. Soc.

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We carried out a dynamical study of the galaxy cluster pair A3407 & A3408 based on a spectroscopic survey obtained with the 4 meter Blanco telescope at the CTIO, plus 6dF data, and ROSAT All-Sky-Survey. The sample consists of 122 member galaxies brighter than m R = 20. Our main goal is to probe the galaxy dynamics in this field and verify if the sample constitutes a single galaxy system or corresponds to an ongoing merging process. Statistical tests were applied to clusters members showing that both the composite system A3407 + A3408 as well as each individual cluster have Gaussian velocity distribution. A velocity gradient of ∼ 847 ± 114 km s −1 was identified around the principal axis of the projected distribution of galaxies, indicating that the global field may be rotating. Applying the KMM algorithm to the distribution of galaxies we found that the solution with two clusters is better than the single unit solution at the 99% c.l. This is consistent with the X-ray distribution around this field, which shows no common X-ray halo involving A3407 and A3408. We also estimated virial masses and applied a two-body model to probe the dynamics of the pair. The more likely scenario is that in which the pair is gravitationally bound and probably experiences a collapse phase, with the cluster cores crossing in less than ∼1 h −1 Gyr, a pre-merger scenario. The complex X-ray morphology, the gas temperature, and some signs of galaxy evolution in A3408 suggests a post-merger scenario, with cores having crossed each other ∼ 1.65h −1 Gyr ago, as an alternative solution.

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Section: Velocity Gradientsupporting

confidence: 91%

Dynamical analysis of the cluster pair: A3407 + A3408

Nascimento

Ribeiro

Trevisan

et al. 2016

Mon. Not. R. Astron. Soc.

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“…real substructures in clusters. First, we checked for a velocity gradient in the set of the 87 fiducial cluster members (see, e.g., den Hartog & Katgert 1996;Girardi et al 1996). We found a significant (at the 96% c.l.)…”

Section: D Analysis: Combining Spatial and Velocity Informationmentioning

confidence: 98%

Structure of Abell 1995 from optical and X-ray data: a galaxy cluster with an elongated radio halo

Boschin

Girardi

Barrena

2012

A&A

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Context. Abell 1995 is a puzzling galaxy cluster hosting a powerful radio halo, but it has not yet been recognized as a obvious cluster merger, as usually expected for clusters with diffuse radio emission. Aims. We aim at an exhaustive analysis of the internal structure of Abell 1995 to verify that this cluster is really dynamically relaxed, as reported in previous studies. Methods. We base our analysis on new and archival spectroscopic and photometric data for 126 galaxies in the field of Abell 1995. The study of the hot intracluster medium was performed on X-ray archival data. Results. Based on 87 fiducial cluster members, we have computed the average cluster redshift z = 0.322 and the global radial velocity dispersion σ V ∼ 1300 km s −1 . We detect two main optical subclusters separated by 1.5 that cause the known NE-SW elongation of the galaxy distribution and a significant velocity gradient in the same direction. As for the X-ray analysis, we confirm that the intracluster medium is mildly elongated, but we also detect three X-ray peaks. Two X-ray peaks are offset with respect to the two galaxy peaks and lie between them, thus suggesting a bimodal merger caught in a phase of post core-core passage. The third X-ray peak lies between the NE galaxy peak and a third, minor galaxy peak suggesting a more complex merger. The difficulty of separating the two main systems leads to a large uncertainty on the line-of-sight (LOS) velocity separation and the system mass: ΔV rf,LOS = 600-2000 km s −1 and M sys = 2-5 × 10 15 h −1 70 M , respectively. Simple analytical arguments suggest a merging scenario for Abell 1995, where two main subsystems are seen just after the collision with an intermediate projection angle. Conclusions. The high mass of Abell 1995 and the evidence of merging suggest it is not atypical among clusters with known radio halos. Interestingly, our findings reinforce the previous evidence for the peculiar dichotomy between the dark matter and galaxy distributions observed in this cluster.

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“…Assuming a singular isothermal profile Carlberg, Yee, & Ellingson (1997) derive the following correlation between r 200 and the cluster mean velocity dispersion: r 200 = 3 1/3 /10 H 0 (z). We have followed an analysis similar to that proposed by den Hartog & Katgert (1996) and Jing & Börner (1996), consisting of the computation of the ratios of at different distances from the cluster center. Both den Hartog & Katgert (1996) and Jing & Börner (1996) use the radius in megaparsecs (up to 3 and 1 Mpc h À1 , respectively).…”

Section: Velocity Dispersion Profilesmentioning

confidence: 99%

“…We have followed an analysis similar to that proposed by den Hartog & Katgert (1996) and Jing & Börner (1996), consisting of the computation of the ratios of at different distances from the cluster center. Both den Hartog & Katgert (1996) and Jing & Börner (1996) use the radius in megaparsecs (up to 3 and 1 Mpc h À1 , respectively). We propose the use of a normalized radius and four bins for the computation of the velocity dispersion estimates 1 , 2 , 3 , and 4 : r/r 200 < 1, r/r 200 < 2, r/r 200 < 3, and r/r 200 7, respectively.…”

Section: Velocity Dispersion Profilesmentioning

confidence: 99%

Velocity Dispersions and Cluster Properties in the Southern Abell Redshift Survey Clusters. II.

Muriel¹,

Quintana²,

Infante³

et al. 2002

The Astronomical Journal

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We report an analysis of the dynamical structure of clusters of galaxies from a survey of photometric and spectroscopic observations in the fields of southern Abell clusters. We analyze the galaxy velocity field in extended regions up to 7 h À1 Mpc from cluster centers, and we estimate mean velocity dispersions and their radial dependence. Only one from a total of 41 Abell clusters does not correspond to a dynamically bound system. However, four of these bound objects are double clusters. We estimate that 20% (seven clusters) of the 35 remaining are subject to serious projection effects. Normalizing the clustercentric distances by means of the overdensity radius r 200 , and the velocity dispersion profiles (VDPs) by the corresponding mean cluster velocity dispersion, we computed the average VDP. Our results indicate a flat behavior of the mean VDP at large distances from the cluster center. Nevertheless, we found that for the inner part of the clusters (r/r 200 1) the VDP is up to 10% smaller than at larger radii.

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On the dynamics of the cores of galaxy clusters

Cited by 141 publications

References 0 publications

Dynamical analysis of the cluster pair: A3407 + A3408

Dynamical analysis of the cluster pair: A3407 + A3408

Structure of Abell 1995 from optical and X-ray data: a galaxy cluster with an elongated radio halo

Velocity Dispersions and Cluster Properties in the Southern Abell Redshift Survey Clusters. II.

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