Deep 230–470 MHz VLA observations of the mini-halo in the Perseus cluster

Abstract

We present a low-frequency view of the Perseus cluster with new observations from the Karl G. Jansky Very Large Array (JVLA) at 230-470 MHz. The data reveal a multitude of new structures associated with the mini-halo. The mini-halo seems to be influenced both by the AGN activity as well as by the sloshing motion of the cool core cluster's gas. In addition, it has a filamentary structure similar to that seen in radio relics found in merging clusters. We present a detailed description of the data reduction and imaging process of the dataset. The depth and resolution of the observations allow us to conduct for the first time a detailed comparison of the mini-halo structure with the X-ray structure as seen in the Chandra X-ray images. The resulting image shows very clearly that the mini-halo emission is mostly contained behind the western cold front, similar to that predicted by simulations of gas sloshing in galaxy clusters, but fainter emission is also seen beyond, as if particles are leaking out. However, due to the proximity of the Perseus cluster, as well as the quality of the data at low radio frequencies and at X-ray wavelengths, we also find evidence of fine structure. This structure includes several radial radio filaments extending in different directions, a concave radio structure associated with the southern X-ray bay and sharp radio edges that correlate with X-ray edges. Mini-halos are therefore not simply diffuse, uniform radio sources, but rather have a rich variety of complex structures. These results illustrate the high-quality images that can be obtained with the new JVLA at low radio-frequencies, as well as the necessity to obtain deeper, higher-fidelity radio images of mini-halos in clusters to further understand their origin.

On the impact of magnetic-field models in galaxy clusters on constraints on axion-like particles from the lack of irregularities in high-energy spectra of astrophysical sources

“…[52] presents a map of rotation measurements across the cluster (not used in previous studies). We recall numerous radio and X-ray observations indicating the presence of an X-ray cavity, or a radio mini-halo, around NGC 1275, consistent with the lobe-environment interaction [53,54,55,56]. An analytical model of the regular magnetic field in such a cavity was presented (and supported by numerical simulations) in Ref.…”

Diffuse Radio Emission from Galaxy Clusters

“….]. Right panel: VLA 230-470 MHz image of the relaxed cool core Perseus cluster from Gendron-Marsolais et al (2017). XMM-Newton X-ray contours in the 0.4-1.3 keV band are overlaid in white with the same contour spacing as in the left panel.…”

Is there a giant Kelvin–Helmholtz instability in the sloshing cold front of the Perseus cluster?

“…The data reduction was performed with CASA (Common Astronomy Software Applications). A pipeline has been specifically developed to reduce this dataset and is presented in detail in Gendron-Marsolais et al (2017).…”