Spectral separation image produced using a technique related to that of spectral tomography to highlight the flatter and steeper components in CIZA0107. Credit: arXiv (2024). DOI: 10.48550/arxiv.2412.15015
Using the Very Large Array (VLA), an international team of astronomers has observed a nearby galaxy merger known as CIZA J0107.7+5408. Results of the observation campaign, presented on December 20 on the preprint server arXivcould help us better understand the merger processes taking place between galaxy clusters.
Galaxy clusters contain thousands of galaxies that are connected by gravity. They typically arise as a result of mergers and grow through the creation of subclusters. These processes provide an excellent opportunity to study matter under conditions that cannot be investigated in laboratories on Earth. Especially the merging clusters of galaxies could help us better understand the physics of shock cold fronts seen in the diffuse medium within clusters, the acceleration of cosmic rays in clusters, and the self-interaction properties of dark matter.
At a redshift of about 0.1, CIZA J0107.7+5408, or CIZA0107 for short, is a nearby, post-nucleus passage, dissociative binary cluster merger. It is a large, approximately equally mass-perturbed system consisting of two subclusters, which house two optical density peaks, with associated but compensated X-ray emission peaks.
A group of astronomers led by Emma Schwartzmann of the US Naval Research Laboratory in Washington, DC, examined CIZA0107 with VLA to shed more light on its properties.
“We present new 240-470 MHz and 2.0-4.0 GHz Very Large Array observations from CIZA0107. We image the diffuse emission in high resolution, constrain its integrated spectrum and map its spectral index distribution,” the researchers wrote in the article.
The new VLA observations confirmed the complex dynamic state of CIZA0107. The images show a dramatically disrupted merger system with a merger axis along the northeast-southwest direction.
The observations at 340 MHz and 3.0 GHz show diffuse radio emission on a scale of about 1.6 million light-years in each of the two subclusters of CIZA0107. At 340 MHz, the astronomers also observed emission from two ultra-steep spectrum regions northwest and southeast of the diffuse spectrum. broadcasting peak in the southwestern subcluster.
Furthermore, the study found that the two subclusters have a similar spectral index of approximately -1.3. For the ultra-steep spectrum regions, the researchers measured steeper spectral slopes between 74 MHz and 340 MHz of approximately −2.2 and −2.9 for the northwestern and southeastern regions, respectively.
The observations also showed that the diffuse emission associated with the southwestern subcluster exhibits a sharp radio edge at 340 MHz. However, at 3.0 GHz the diffuse emission does not show any feature at the location of the 340 MHz radio edge and the X-ray shock front, and in fact extends beyond the shock.
In summary, the authors of the paper underlined that the properties of the emission in CIZA0107 suggest that the system may harbor a double halo structure, or that the emission originates from two relics projected onto the central cluster regions.
More information:
Emma Schwartzman et al, Multi-frequency radio observations of the dissociative cluster merger CIZA J0107.7+5408, arXiv (2024). DOI: 10.48550/arxiv.2412.15015
Magazine information:
arXiv
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Quote: Observers investigate a nearby merger of galaxy clusters (2024, December 30), retrieved December 30, 2024 from
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