New giant radio galaxy discovered with MeerKAT

19 Nov 2024, 13:45 by Tomasz Nowakowski

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The optical HSC DR2 Wide combined 𝑔, 𝑟, 𝑖 band image of MGTC J100022.85+031520.4. Credit: Charlton et al., 2024.

An international team of astronomers has employed the MeerKAT radio telescope to investigate giant radio galaxies in the field of the Cosmological Evolution Survey (COSMOS). They found a new giant radio galaxy that had not been reported before. The finding was presented in a research paper published November 11 on the pre-print server arXiv.

The so-called giant radio galaxies (GRGs) are radio galaxies with an overall projected linear length exceeding at least 2.3 million light years. They are rare objects grown usually in low-density environments and are observed to display jets and lobes of synchrotron-emitting plasma. GRGs are important for astronomers to study the formation and the evolution of radio sources.

The MeerKAT radio interferometer located in South Africa is an excellent instrument to study GRGs at high frequencies (about 1.0 GHz). That is why a group of astronomers led by Kathleen Charlton of the University of Cape Town in South Africa, has used MeerKAT to inspect known GRGs in the COSMOS field. The study was conducted as part of the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey.

"We have presented spatially-resolved spectral index and age maps of three GRGs within the COSMOS field using MIGHTEE L-band data and new MeerKAT UHF band observations," the researchers wrote in the paper.

Charlton's team investigated three giant radio galaxies with the MeerKAT telescope. One of them turned out to be identified for the first time and received the designation MGTC J100022.85+031520.4.

According to the study, MGTC J100022.85+031520.4 is hosted by an elliptical galaxy, SDSS J100022.85+031520, with a redshift of approximately 0.1034. The new GRG has a projected linear size of about 4.2 million light years, a mass of 93 trillion solar masses, and a total power of 597 ZW/Hz at 1,284 MHz.

The collected data indicate that MGTC J100022.85+031520.4 has a dynamical age of about one billion years and its jet has a power at a level of one million QW.

The observations found that MGTC J100022.85+031520.4 is the central galaxy and brightest cluster galaxy (BCG) in the galaxy cluster WHL J100022.9+031521. Therefore, it makes it one of only 4% of GRGs known to reside in cluster environments.

Summing up the results, the authors of the paper noted that the location of MGTC J100022.85+031520.4 at the center of the cluster and the observed bent morphology in the top lobe suggests that it has similar properties to galaxies hosting wide-angle-tail (WAT) radio sources.

In general, WAT radio sources are powerful and often located in the centers of galaxy clusters where intracluster medium ram pressure may bend the lobes into their characteristic C-shape.

More information: K. K. L. Charlton et al, A spatially-resolved spectral analysis of giant radio galaxies with MeerKAT, arXiv (2024). DOI: 10.48550/arxiv.2411.06813

Journal information: arXiv