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Astronomers investigate X-shaped radio galaxy 3C 315

By analyzing the data from Leahy's atlas of double radio-sources and NASA/IPAC Extragalactic Database (NED), Serbian astronomers have explored an X-shaped radio galaxy designated 3C 315. Results of the new study, March 10 on the arXiv preprint server, shed more light on the properties and morphology of this galaxy.

Radio galaxies emit huge amounts of radio waves from their central cores. Black holes at the centers of these galaxies accrete gas and dust, generating high-energy jets visible in radio wavelengths, which accelerate electrically charged particles to high velocities. Some radio galaxies showcase an X-shaped radio morphology that could be caused, for instance, by an active galactic nucleus (AGN) that has undergone two separate epochs of activity.

There are also radio galaxies that may be double radio sources associated with galactic nuclei (DRAGNs). They are clouds of radio-emitting plasma that have been shot out of AGN via narrow jets.

3C 315 is a highly polarized prototype X-shaped (winged) DRAGN, exhibiting two sets of double lobes angled with respect to each other. It is highly elongated in the northwest-southeast direction and accompanied by an elliptical galaxy.

Previous observations of 3C 315 have found that in addition to its peculiar structure, it also exhibits unusual spectral behavior. Recently, a team of astronomers, led by Vesna Borka Jovanović of the University of Belgrade in Serbia, investigated this source in detail in order to get more insights into its unique properties.

Jovanović and colleagues managed to obtain spectral index distributions derived between two frequencies: 1,417 and 2,695 MHz, as well as between 1,646 and 2,695 MHz. They observed how these distributions change over the whole area of 3C 315.

In particular, the spectral index map of 3C 315 shows that the spectral index has strong variability over three studied paths that were designated by astronomers from north-northeast to south-southwest. However, it turned out that the average value of the spectral index is different along each of these paths.

According to the study, the spectral index over the area of 3C 315 is almost always higher than zero, except in only a few small parts of the galaxy where it is negative. Based on this finding, the researchers concluded that the non-thermal (synchrotron) emission is the most dominant radiation mechanism over the whole source.

The research also found that 3C 315 contains a pronounced and bright radio core, as well as weak hotspots. The outer structure of the source appears to be relaxed. Given that 3C 315 and its accompanying elliptical galaxy are both located inside a cluster, the authors of the paper assume that the environment probably plays the most significant role in the evolution of this radio galaxy.