June 13, 2021

Black holes alter the evolution of nearby galaxies


Example of a nearby spiral galaxy, M81, where the bulge, the reddish central part, is easily identified.

Example of a nearby spiral galaxy, M81, where the bulge, the reddish central part, is easily identified.
EP

The black holes alter the evolution of your galaxy but also that of nearby galaxies, according to a study led by Ignacio Martin Navarro, a researcher at the Institute of Astrophysics of the Canary Islands (IAC) and who this Wednesday publishes the journal Nature.

The study, initiated during Ignacio Martín’s stay at the Max Planck Institute for Astrophysics, in Germany, sought to find out if the matter and energy radiated by black holes is capable of altering the evolution not only of the host galaxy, but also also of those that are around him.

In a statement from the IAC it is explained that in the heart of each galaxy massive enough there is a black hole whose gravitational field, although very intense, affects only a small region around the galactic center.

Despite the fact that these astronomical objects are billions of times smaller than the host galaxies, the current conception of the Universe is only understood if the evolution of galaxies is regulated by the activity of black holes, since, without them, it is not possible to explain the observed properties of galaxies.

Theoretical predictions suggest that as black holes grow, they generate enough energy to heat and expel gas in galaxies over great distances.

Observing and describing the mechanism by which this energy interacts with galaxies, modulating their evolution is therefore a fundamental question in current astrophysics.

With this objective in mind, the study led by Ignacio Martín has taken a step further and has tried to find out if the matter and energy radiated by black holes is capable of altering that of satellite galaxies as well.

To do this, the team has made use of the Sloan Digital Sky Survey mapping, which has allowed them to analyze the properties of galaxies in thousands of groups and clusters.

“Surprisingly we have found that satellite galaxies form more or fewer stars depending on their orientation with respect to the central galaxy”, explains Annalisa Pillepich, researcher at the Max Planck Institute for Astronomy (MPIA, Germany) and co-author of the work.

To try to explain this geometric effect on the properties of satellite galaxies, the scientists resorted to a cosmological simulation of the Universe called Illustris-TNG, which in its code implements a particular treatment for the interaction between black holes and host galaxies.

“As in the observations, the Illustris-TNG simulation shows a clear modulation in star formation rate satellite galaxies depending on their position relative to the central one “, adds Annalisa Pillepich.

The statement adds that the relevance of the result is twofold because it gives observational support to the idea that black holes play an important role in regulating the evolution of galaxies, a fundamental pillar in the current knowledge of the Universe.

However, this hypothesis is continually questioned given the difficulty to, in practice, measure the possible effect of black holes in real galaxies, beyond theoretical considerations.

The results of the study suggest that there is a particular type of coupling between galaxies and black holes, by means of which they are capable of expelling material at great distances from the galactic centers, even altering the evolution of other nearby galaxies.

“Therefore, beyond observing the effect of black holes on the evolution of galaxies, our analysis opens a door to understand the details of this interaction”, points out Ignacio Martín Navarro.

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