Wide-Ranging Bent Radio Jet Discovered in Merging Galaxy Cluster Abell 514, Provides Insights on Host Properties and External Environment

A team of researchers led by Wonki Lee from Yonsei University in Seoul, South Korea, embarked on an exploration of the galaxy cluster Abell 514 (A514). Their discoveries shed light on a remarkable phenomenon happening within this merging galaxy cluster.

What is Abell 514?

Galaxy clusters refer to the largest gravitationally bound structures made of up to thousands of galaxies held together by gravity. They play a crucial role in understanding the large-scale structure formation and evolution of the universe. Since the clusters of galaxies generally form by the gravitational merger of smaller clusters and groups, they represent the most energetic events in the universe since the Big Bang.

Abell 514 is a merging galaxy cluster discovered in 1958 at a redshift of approximately 0.07. It has a mass of about 300 trillion solar masses and an overall temperature of 3.8 keV, with metallicity estimated at a level of 0.22. Previous observations of this galaxy cluster revealed that A514 has a rich morphology and hosts various extended radio sources. A514 is also among the galaxy clusters which are extensively studied by astronomers using radio observations.

This complex group of galaxies represents an interesting merger cluster with lots of substructures that are visible in the X-ray image and in the temperature and abundance distributions. It also contains six extended and polarized radio sources located at different projected distances from the cluster center.

New Insights on a Complex Galaxy Cluster

In this study, the astronomers have conducted deep low-frequency radio observations using the upgraded Giant Metrewave Radio Telescope (uGMRT). They used Band 2 (125-250 MHz), Band 3 (250-500 MHz), and Band 4 (550-850 MHz) with on-source integration times of 3.5, 3.7, and 4.3 hours, respectively.

The research team found that radio emissions from one of three radio galaxies in Abell 514, known as PKS 0446-20, originates from the two radio lobes of the active galactic nucleus (AGN) and extends toward the southern periphery. The largest linear size of this bent jet was measured to be about 2.3 million light years.

The images gathered with uGMRT reveal that two radio lobes are connected to the 1,300-light-years-long north-south structure which was dubbed "the bridge". The southern end of the bridge connects with the 1,000-light-years-long "arc" which is concave toward the center of the cluster. Meanwhile, the eastern end of the arc touches the northern end of the 1,300-light-years-long tail.

Lee and his team also detected a discontinuity in X-ray surface brightness and high polarization at the location of the extended radio emission in Abell 514. According to the researchers, this is a result of the jet plasma redistribution along the cold front of the recent cluster merger.

As explained by the experts, a plasma bubble, injected during an off-axis cluster merger, can undergo stretching along the cold front of the infalling cluster. They believe that the stretching process results in an extended radio emission which resembles the observation in Abell 514. At the late merger phase, the bubble redistributes at the cluster outskirt with its elongation aligned tangential to the cluster.