Discovery of a pre-merger shock in an intercluster filament in Abell 98

Abstract

We report the first unambiguous detection of an axial merger shock in the early-stage merging cluster Abell 98 using deep (227 ks) Chandra observations. The shock is about 420 kpc south from the northern subcluster of Abell 98, in between the northern and central subclusters, with a Mach number of M $\approx$ 2.3 $\pm$ 0.3. Our discovery of the axial merger shock front unveils a critical epoch in the formation of a massive galaxy cluster, when two subclusters are caught in the early phase of the merging process. We find that the electron temperature in the post-shock region favors the instant collisionless model, where electrons are strongly heated at the shock front, by interactions with the magnetic field. We also report on the detection of an intercluster gas filament, with a temperature of kT = 1.07 $\pm$ 0.29 keV, along the merger axis of Abell 98. The measured properties of the gas in the filament are consistent with previous observations and numerical simulations of the hottest, densest parts of the warm-hot intergalactic medium (WHIM), where WHIM filaments interface with the virialization regions of galaxy clusters.

Accepted for publication in The Astrophysical Journal Letters

References in corpus (10)

• Shocks and cold fronts in galaxy clusters
• The Search for the Missing Baryons at Low Redshift
• Detection of hot gas in the filament connecting the clusters of galaxies Abell 222 and Abell 223
• Chandra observation of two shock fronts in the merging galaxy cluster Abell 2146
• A $\mathcal{M}\gtrsim 3$ shock in `El Gordo' cluster and the origin of the radio relic
• The Abell 3391/95 galaxy cluster system: A 15 Mpc intergalactic medium emission filament, a warm gas bridge, infalling matter clumps, and (re-) accelerated plasma discovered by combining SRG/eROSITA data with ASKAP/EMU and DECam data
• Detection of missing baryons in galaxy groups with kinetic Sunyaev-Zel'dovich effect
• Observations of a Pre-Merger Shock in Colliding Clusters of Galaxies
• Evolution of Splashback Boundaries and Gaseous Outskirts: Insights from Mergers of Self-similar Galaxy Clusters
• Merger Signatures in the Galaxy Cluster Abell 98

Cited by in corpus (10)

• The eROSITA view of the Abell 3391/95 field: Cluster Outskirts and Filaments
• Gas sloshing and cold fronts in pre-merging galaxy cluster Abell 98
• The effect of cluster dynamical state on ram-pressure stripping
• Suzaku Observations of the Cluster Outskirts and Intercluster Filament in the Triple Merger Cluster Abell 98
• Discovery of a >13 Mpc long X-ray filament between two galaxy clusters beyond three times their virial radii
• The warm-hot intergalactic medium in inter-cluster filaments -- A forecast for HUBS observations based on eRASS1 superclusters
• Advancing Precision Particle Background Estimation for Future X-ray Missions: Correlated Variability between AMS and Chandra/XMM-Newton
• X-ray and optical analysis of the distant, merging double cluster SPT-CLJ2228-5828, its gas bridge, and shock front
• The thermodynamic structure and large-scale structure filament in MACS J0717.5+3745
• Cosmological simulation of a radio synchrotron bridge between pre-merging galaxy clusters