X-Ray observations of a subhalo associated with the NGC 4839 group infalling toward the Coma cluster

Abstract

We report $Suzaku$ X-ray observations of the dark subhalo associated with the merging group of NGC 4839 in the Coma cluster. The X-ray image exhibits an elongated tail toward the southwest. The X-ray peak shifts approximately $1^{\prime }$ away from the weak-lensing mass center toward the opposite direction of the Coma cluster center. We investigated the temperature, normalization, pressure, and entropy distributions around the subhalo. Excluding the X-ray tail, the temperature beyond the truncation radius is 8-10$\mathrm{keV}$, which is two times higher than that of the subhalo and the X-ray tail. The pressure is nearly uniform excluding southern part of the subhalo at two times of the truncation radius. We computed the gas mass within the truncation radius and the X-ray tail. While the gas fraction within the truncation radius is about 5 times smaller than that of regular groups, the gas mass in the subhalo and the X-ray tail to weak-lensing mass ratio is consistent with that of regular groups. Assuming the infall velocity, $2000\mathrm{km}{\mathrm{s}}^{-1}$, the ram pressure is 1.4 times greater than gravitational force per unit area. Assuming the Kelvin-Helmholtz instabilities, the total lost mass is approximately $3\times 10^{11}{M}_{\odot }$. If this gas had originally been within the truncation radius, the gas mass fraction of the subhalo would have been comparable with those of regular groups before infalling to the Coma cluster.

15 pages, 20 figures, PASJ in press

References in corpus (9)

• A direct empirical proof of the existence of dark matter
• Shocks and cold fronts in galaxy clusters
• Observations of extended radio emission in clusters
• The origin of cold fronts in the cores of relaxed galaxy clusters
• Radial temperature profiles for a large sample of galaxy clusters observed with XMM-Newton
• Chandra observation of two shock fronts in the merging galaxy cluster Abell 2146
• The stripping of a galaxy group diving into the massive cluster A2142
• The growth of the galaxy cluster Abell 85: mergers, shocks, stripping and seeding of clumping
• The bow shock, cold fronts and disintegrating cool core in the merging galaxy group RXJ0751.3+5012

Cited by in corpus (6)

• Science objectives of the Einstein Probe mission
• Deep Chandra observations of the stripped galaxy group falling into Abell 2142
• A New Class of X-Ray Tails of Early-Type Galaxies and Subclusters in Galaxy Clusters - Slingshot Tails vs Ram Pressure Stripped Tails
• Globular Clusters in NGC 4839 Falling into Coma: Evidence for the Second Infall?
• A Redshift Survey of the Coma Cluster (A1656): Understanding the Nature of Subhalos in the Weak-lensing Map
• Imaging-spectroscopy diagnosis of the giant sloshing spiral in the Virgo cluster with the Einstein Probe Follow-up X-ray Telescope