Cosmic web influences the evolution of galaxies

(ORDO NEWS) — The shape of galaxies and the features of their evolution depend on the properties of the “web” of cosmic filaments that stretches throughout the Universe. The cosmic web plays a larger role than previously thought, according to a new study.

In the Universe, galaxies are distributed along the filaments of the cosmic web – a complex network of filaments consisting of ordinary and dark matter. And at the intersections of filaments, clusters of galaxies are formed – groups of hundreds or even thousands of galaxies gravitationally bound to each other.

They are the largest groups of objects in the Universe, connected by gravitational forces. However, the specific nature of the influence of filaments on the properties of galaxies has been studied only very poorly so far.

To better understand the mechanism of this effect, an international team of astronomers led by Pascale Jablonka, professor at the Federal Polytechnic School of Lausanne, Switzerland, studied the vast surroundings of the Virgo cluster of galaxies located in the local universe. This cluster contains approximately 1,500 galaxies and lies about 65 million light-years away from our own Milky Way galaxy.

The authors analyzed the properties of the galaxies surrounding the Virgo cluster within a region 12 times the size of the main cluster.

As a result, a set of 7,000 galaxies was studied, including 250 galaxies large enough to accurately estimate their gas content. The measurements were made using a decameter radio telescope located in the commune of Nance, France, and a 30-meter IRAM telescope, Spain.

As a result of the analysis, it was found that the properties of galaxies – namely, their shape, star formation rate, gas content, age and metallicity of stars – change smoothly when moving from isolated galaxies to galaxies in filaments, and then to galaxies that are part of clusters.

From this point of view, filaments can be thought of as a transitional medium in which galaxies undergo “preprocessing” before falling into a cluster of galaxies.

In this environment, the formation of stars slows down or stops altogether, elliptical galaxies appear, the amount of atomic and molecular hydrogen in galaxies decreases, which indicates the end of the active period of galaxy development.

Scientists observed that the evolution of galaxies along the coordinate of their life cycle corresponds to the local distribution density of galaxies: galaxies that do not form new stars or form only a small number of them account for less than 20 percent of the number of isolated galaxies studied in the work, however, in the set of galaxies located inside filaments, the same group accounts for 20-60 percent of the number of all galaxies, and in the set of galaxies, the Virgo clusters are even almost 80 percent.

These findings open up new prospects for the development of theories of the evolution of galaxies in the context of their interaction with the largest structures of the Universe, the authors note.

Two new papers by the Yablonka team have been published in the Astrophysical Journal and Astronomy & Astrophysics, respectively.

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