Galaxy cluster's rotation

Abstract

We study the possible rotation of cluster galaxies, developing, testing and applying a novel algorithm which identifies rotation, if such does exist, as well as its rotational centre, its axis orientation, rotational velocity amplitude and, finally, the clockwise or counterclockwise direction of rotation on the plane of the sky. To validate our algorithms we construct realistic Monte Carlo mock rotating clusters and confirm that our method provides robust indications of rotation. We then apply our methodology on a sample of Abell clusters with z 0.1 with member galaxies selected from the Sloan Digital Sky Survey (SDSS) DR10 spectroscopic data base. After excluding a number of substructured clusters, which could provide erroneous indications of rotation, and taking into account the expected fraction of misidentified coherent substructure velocities for rotation, provided by our Monte-Carlo simulation analysis, we find that ∼ 23% of our clusters are rotating under a set of strict criteria. Loosening the strictness of the criteria, on the expense of introducing spurious rotation indications, we find this fraction increasing to ∼ 28%. We correlate our rotation indicators with the cluster dynamical state, provided either by their Bautz-Morgan type or by their Xray isophotal shape and find for those clusters showing rotation within 1.5 h −1 70 Mpc that the significance of their rotation is related to the dynamically younger phases of cluster formation but after the initial anisotropic accretion and merging has been completed. Finally, finding rotational modes in galaxy clusters could lead to the necessity of correcting the dynamical cluster mass calculations.

Messier 81’s Planck view versus its halo mapping

“…In order to account for the detected temperature anisotropy, however, the M81 halo should be filled by a relatively large amount of gas (likely in the form of cold gas clouds), as in the models proposed, e.g., by Pfenniger et al (1994);De Paolis et al (1995a); Gerhard & Silk (1996). A viable explanation of the detected effect could be, in principle, also the rotational kinematic Sunyaev-Zel'dovich (rkSZ) effect, which is known to be active on galaxy cluster scales (Cooray et al 2002;Chluba et al 2002;Manolopoulou et al 2017). Naturally, to be active, the rkSZ effect does require the presence of a conspicuous population of high energy electrons in the rotating M81 halo.…”

Dynamical analysis of the cluster pair: A3407 + A3408

“…First of all, we should keep in mind that the two-body model does not consider the angular moment of the system, which is unlikely to be zero, since we have identified a velocity assymetry around the principal axis of the galaxy projected distribution, suggesting a rotating object. The reason this could be important to any dynamical analysis is that the corrected cluster mass can be reduced by ∼20%-30%, on average, with respect to that uncorrected for rotation, as shown in Manolopoulou & Plionis (2016). An additional weakness of the two-body model is not considering the distribution of matter inside each cluster.…”

The effect of rotation on the thermal instability of stratified galactic atmospheres – I. Local analysis

“…Also note that in some clusters the rotation pattern may be hidden because the system is viewed face on, as suggested in the case of Abell 1835 by McNamara et al (2014). It has also been suggested that a significant fraction (∼ 25%) of clusters may rotate coherently on Mpc scales with typical velocities of a few hundreds of km s −1 (Manolopoulou & Plionis 2017; see also Bianconi et al 2013). Finally, the presence of cool core cold fronts, i.e.…”