First image of a collision of particles and galaxies

Researchers at Clemson University College of Science in South Carolina, associated with an international college of astronomers, produced the first photographic evidence of a relativistic jet from two colliding galaxies. The merging of galaxies can produce jets of charged particles which move at a speed close to that of light.

Researchers at Clemson University College of Science in South Carolina, in collaboration with international astronomers, had previously observed that jets were present in certain elliptical galaxies formed by the fusion of two spiral galaxies.

These same scientists now hold the photograph of a jet from two younger spiral-shaped galaxies. The team consists mainly of Vaidehi Paliya, former postdoc researcher at Clemson University, now researcher at the Deutsches Elektronen Synchrotron (DESY) in Germany (and main author of the results reported in the Astrophysical Journal of April 7, 2020), of the professor Associate Marco Ajello, Professor Dieter Hartmann and Assistant Professor Stefano Marchesi of the Department of Physics and Astronomy of the same Clemson University, entitled the report of this work: “TXS 2116-077: a relativistic jet emitting gamma rays hosted in a fusion of galaxies “.

The shock of galaxies …

The fact of having chosen the collision of two young galaxies allowed the researchers to clearly see the jet in question, because less obscuring. Usually a jet emits such a powerful light that it hides the galaxies behind it. Professor Stefano Marchesi explains that the exercise is the same as trying to observe an object in the distance while someone projects a flashlight at you, right in your eyes. There, the researchers were able to observe both the jet and the galaxies colliding.

Jets are the most powerful astrophysical phenomena in the Universe. They can emit more energy in the form of radiation, like X-rays and gamma rays than our Sun will produce during its entire life.

The image captured by the Vaidehi Paliya team, using the 8.2-meter Subaru optical infrared telescope, located on the island of Hawaii, is that of two galaxies: a Seyfert 1 galaxy, known as name of TXS 2116-077, and another similar mass galaxy. The details obtained in the photo made it possible to see that they collided for the second time. The index allowing this deduction is the quantity of gas seen on the image. Other observations with the Gran Telescopio Canarias and William Herschel on the island of La Palma, off the Spanish coast, as well as with the NASA Chandra X-Ray Observatory space telescope were necessary.

As far as we are concerned, in several billion years our own Milky Way will merge with the Andromeda galaxy. Detailed simulations suggest that this event will lead to the formation of a giant elliptical galaxy. This collision, under certain physical conditions, could also host a relativistic jet.

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