Astronomers Spot Radio Halo in Massive Galaxy Cluster
A global team of astronomers conducted radio observations of the large galaxy cluster ACT-CL J0329.2-2330, uncovering a new radio halo within the cluster. The discovery was detailed in a research paper published on April 5 on the pre-print server arXiv.
In fact, radio halos are vast areas of diffuse radio emissions typically located at the cores of large galaxy clusters, often displaying a consistent structure that mirrors the X-ray emitting intracluster medium (ICM).
Challenges and Improvements in Detecting Low Surface Brightness Emissions
Detecting these emissions can be challenging due to their low surface brightness, especially at GHz frequencies. However, their visibility improves at lower frequencies.
A team of astronomers, led by Sinenhlanhla Precious Sikhosana from the University of KwaZulu-Natal in Durban, South Africa, has identified a new radio halo in ACT-CL J0329.2-2330, also known as ACT-CL J0329.
Moreover, This galaxy cluster has a mass of approximately 970 trillion solar masses and a redshift of 1.23. The discovery resulted from L-band and UHF-band observations of the cluster using the MeerKAT radio telescope in the MeerKAT Massive Distant Cluster Survey (MMDCS).
The researchers stated, “In this study, we present MeerKAT L and UHF-band observations of ACT-CL J0329.2-2330, a galaxy cluster at z=1.23. The low-resolution images reveal a radio halo within the cluster. The MeerKAT observations were conducted at L-band with a total on-target time of 3.5 hours, utilizing an 8-second dump rate and 4,096 channels.”
Discovery of Extended Emission in ACT-CL J0329 Through MeerKAT Analysis
However, analyzing MeerKAT images, Sikhosana’s team pinpointed extended emission at the core of ACT-CL J0329, measuring 3.59 million light years across at 1.28 GHz. These images reveal a radio halo with a consistent, smooth structure that mirrors the thermal bremsstrahlung emission from the intracluster medium (ICM).
Based on these findings, the astronomers identified this emission as a radio halo, marking it as the highest redshift halo discovered to date.
The study determined that the newly identified radio halo has a flux density of 3.44 mJy at the L-band and 6.11 mJy at the UHF-band.
The halo has an integrated spectral index of 1.3 and an estimated radio power of 4.4 YW/Hz.
However, these findings indicate that the halo in ACT-CL J0329 exhibits luminosity comparable to halos observed in nearby massive galaxy clusters, supporting the notion of rapid magnetic field amplification in high-redshift galaxy clusters.
To conclude, in their concluding remarks, the researchers highlighted that the spectral index map of ACT-CL J0329 reveals noticeable variations, with higher spectral index values predominantly located in the eastern region. This suggests that turbulent energy dissipation within the halo is not uniform.
Read the original article on: Phys Org
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