A study of 20 radio galaxies offers new information on the activity of the supermassive black holes at their center


An article published in the journal “Astronomy & Astrophysics” reports a study on the properties of the ionized gas that surrounds supermassive black holes in 20 galaxies selected as a sample. A team of researchers led by Barbara Balmaverde of the Italian National Institute of Astrophysics, Turin, used the MUSE spectrograph mounted on ESO’s VLT in Chile to carry out the MURALES (MUse RAdio Loud Emission line Snapshot) survey, which includes the 20 galaxies studied. These are powerful sources of radio emissions thanks to their active galactic nuclei. The mapping of the ionized gas and its interaction with the relativistic jet produced by central black holes helps to understand the mechanisms of growth and interaction with their host galaxies.

Barbara Balmaverde’s team selected 20 radio galaxies – as galaxies with strong radio emissions are called – up to 5 billion light years away from Earth. They’re galaxies included in the Third Cambridge Catalog (3C), which has included radio sources since 1950.

The researchers observed those 20 radio galaxies with the MUSE (Multi Unit Spectroscopic Explorer) instrument on the VLT (Very Large Telescope). The pilot radio galaxy is 3C 317, in the middle of the galaxy cluster Abell 2052, in the composite image (Courtesy Balmaverde et al., Astronomy & Astrophysics. All rights reserved) in three colors: red for X-rays, blue for radio waves and white for optical frequencies.

The interaction between the relativistic jet produced by the supermassive black hole at the center of each of the 20 radio galaxies studied and the gas surrounding it was studied by mapping the ionized gas. This makes it possible to understand first of all how those supermassive black holes feed on the materials that surround them and are eventually swallowed up.

One of the problems studied in recent years is the so-called feedback, the process of exchange of matter and energy between the active galactic nucleus, its host galaxy and the galaxy cluster it’s part of. Depending on the feedback characteristics, that process can favor or inhibit star formation, exerting a significant influence on the evolution of the galaxy in which it occurs. The MUSE spectrograph allowed to see filaments of ionized gas coming out of the galaxy in which they were generated.

Barbara Balmaverde explained that her team’s work went ahead with the study of 20 more radio galaxies, again with distances up to 5 billion light years from Earth. The next step will be to study more distant radio galaxies. She added that the MUSE spectrograph allowed to obtain images of extraordinary quality in just 20 minutes of observation. They can offer new information to understand the processes taking place in an active galactic nucleus, in the area around a supermassive black hole, a truly extreme object with masses of millions and even billions of times the Sun’s.

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