The galaxy wagging its tail

It has a long tail of two and a half million light years – twice as long as previously thought – and it appears to be “wagging its tail.” We’re talking about one of the largest galaxies at the cluster center, Abell 1775, about a billion light-years away from us.

To make this discovery an international team that included several Italian researchersNational Institute of Astrophysics Analyze the collected images using the European Radio Telescope Promises And the X-ray satellite Chandra NASA

The Galaxy clusters They are the most impressive structures in the universe. They surround hundreds to thousands of galaxies bound together by the force of gravity. These orbits are within clusters of remarkable speed, so much so that they can move up to thousands of kilometers in one second. Penetrating the space in which galaxies make their orbits, highly vacuum gas reaches temperatures of tens or even hundreds of millions of degrees and extends for tens of millions of light-years. To study the gas that prevails in galaxy clusters, astronomers have to resort to satellites that scan the sky at high energy, especially in X ray, Radiation absorbed by the Earth’s atmosphere. These observations reveal important information not only about galaxy clusters but also the formation of some strange sources that were recently discovered by analyzing these objects on the other side of the electromagnetic spectrum, in Radio Band.

An international team of researchers combined observations in these two ranges to study the cluster of galaxies Abel 1775, It reveals unprecedented details of this system less than a billion light years from Earth. In the radio range, the group used data from three different radio telescopes including Promises (Low frequency array), A large instrument made up of thousands of antennas distributed in the Netherlands and in several European countries, and is managed by the Dutch Institute ASTRON with an international consortium that also includes the National Institute of Astrophysics (INAF). In x-rays, they targeted the satellite Chandra NASA has been going on for more than a day toward the block.

In the past, radio observations revealed one of the most fascinating phenomena of Abel 1775: the existence of a specific galaxy, with a morphology that astronomers call “yarn”. This galaxy is one of the fastest in mass and hosts an “active” black hole in its center, which swallows up surrounding matter at a rapid rate while expelling part of it in the form of jets with a strong radio range. emission. Due to the high speed of the galaxy and the pressure exerted on it by the surrounding hot gas, these jets “bend” near the black hole, forming a “tail,” a very long path of electrons and magnetic fields.

“In this study, we found that the tail of this galaxy in Abell 1775 extends about 2.5 million light years, which is one of the largest extensions ever observed, and twice the span of previous observations.” Andrea Botion, Researcher at Leiden University, the Netherlands, and INAF assistant, first author of the article describing the findings, published in the journal Astronomy and Astrophysics.

Then astronomers realized that the tail region revealed by the new observations originated near a point where the path of electrons and magnetic fields seemed to be refracted. This is where the tail is Slightly changes directionAs if the galaxy is “wagging its tail.”

“By analyzing Chandra’s X-ray data, we found that this transition point coincides with a region where the hot gas changes sharply in density, and we believe that this is why its tail wiggles,” he adds. Fabio Justallo, INAF researcher in Milan and co-author of the study. “We believe that the density jump is due to the gas movements within the Abel 1775, which were also highlighted by the ‘mushroom’ structure and a gas vortex in the center of the group, which we were able to extract using certain image processing techniques.”

According to the new study, the movements of hot gas within the cluster will be responsible for the formation of other structures discovered by observing Abell 1775 in the radio range, such as filaments near the Head and Tail galaxy.

Article “Non-thermal phenomena in the center of Abell 1775: 800 kpc head-tail, revived fossil plasma and slingshot radio auraIt was published online in the magazine Astronomy and Astrophysics.