Testing the rotation versus merger scenario in the galaxy cluster Abell 2107. Issue 3 (12th March 2019)

• Record Type: Journal Article
• Authors: Liu, Ang; Tozzi, Paolo
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 485:Issue 3(2019)
• Page Start: 3909
• Page End: 3918
• Publication Date: 2019-03-12
• Subjects: galaxies: clusters: intracluster medium -- X-rays: galaxies: clusters; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz713
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We search for global rotation of the intracluster medium in the galaxy cluster Abell 2107, where previous studies have detected rotational motion in the member galaxies with a high-significance level. By fitting the centroid of the iron K α line complex at 6.7–6.9 keV rest frame in Chandra ACIS-I spectra, we identify the possible rotation axis with the line that maximizes the difference between the emission-weighted spectroscopic redshift measured in the two halves defined by the line itself. Then, we measure the emission-weighted redshift in linear regions parallel to the preferred rotation axis, and find a significant gradient as a function of the projected distance from the rotation axis, compatible with a rotation pattern with maximum tangential velocity${\tt v}_{\rm max}=1380\pm 600$ km s −1 at a radius λ0 ∼ 160 kpc. This result, if interpreted in the framework of hydrostatic equilibrium, as suggested by the regular morphology of Abell 2107, would imply a large mass correction of the order of$\Delta M = (6 \pm 4)\times 10^{13} \, \mathrm{M}_\odot$ at ∼160 kpc, which is incompatible with the cluster morphology itself. A more conservative interpretation may be provided by an unnoticed off-centre, head-on collision between two comparable haloes. Our analysis confirms the peculiar dynamical nature of the otherwise regular cluster Abell 2107, but is not able to resolve the rotation versus merger scenario, a science case that can be addressed by the next-generation X-ray facilities carrying X-ray bolometers on board.