Multi-wavelength Observations of the Dissociative Merger in the Galaxy Cluster CIZA J0107.7+5408

TL;DR

This study analyzes a dissociative galaxy cluster merger using multi-wavelength data, revealing shock-related radio relics, temperature peaks, and ultra-steep spectrum emissions, providing insights into dark matter interactions and particle acceleration.

Contribution

It presents a detailed multi-wavelength analysis of a dissociative galaxy cluster merger, highlighting the dynamics of gas, galaxies, dark matter, and radio relics, and introduces potential radio phoenix phenomena.

Findings

Separation of gas and galaxy peaks due to ram pressure effects.

Detection of double radio relics along the merger axis.

Identification of ultra-steep spectrum radio emissions as radio phoenixes.

Abstract

We present results based on X-ray, optical, and radio observations of the massive galaxy cluster CIZA J0107.7+5408. We find that this system is a post core passage, dissociative, binary merger, with the optical galaxy density peaks of each subcluster leading their associated X-ray emission peaks. This separation occurs because the diffuse gas experiences ram pressure forces while the effectively collisionless galaxies (and presumably their associated dark matter halos) do not. This system contains double peaked diffuse radio emission, possibly a double radio relic with the relics lying along the merger axis and also leading the X-ray cores. We find evidence for a temperature peak associated with the SW relic, likely created by the same merger shock that is powering the relic radio emission in this region. Thus, this system is a relatively rare clean example of a dissociative binary merger, which can in principle be used to place constraints on the self-interaction cross-section of dark matter. Low frequency radio observations reveal ultra-steep spectrum diffuse radio emission that is not correlated with the X-ray, optical, or high frequency radio emission. We suggest that these sources are radio phoenixes, which are preexisting non-thermal particle populations that have been re-energized through adiabatic compression by the same merger shocks that power the radio relics. Finally, we place upper limits on inverse Compton emission from the SW radio relic.