Thanks to the Gran Telescopio Canarias (GTC), a pioneering study led by the researcher from the Instituto de Astrofísica de Canarias (IAC) Carlos M. Gutiérrez has identified three compact groups of galaxies located aboutfive billion light years from Earth.
Galaxies can appear isolated or form clusters of thousands of them. In those groups in which the galaxies are very close to each other, compact configurations of between four and ten members are formed. Over the past two decades, the astrophysical community has managed to identify a hundred of these compact groups up to a distance of one billion light years. This week, The magazineAstrophysical Journal Letterspublishes a study, directed by Carlos M. Gutiérrez, on the detection and analysis ofthe three most distant compact groups of galaxies observed to date.
“These compact groups are the ideal setting to studyhow the presence of close companions affects the natural evolution of galaxies. This closeness can drastically alter the relatively placid life of galaxies, since the action of gravity subjects them to processes such as deformations, dislodging, etc. In certain cases, even the galaxies themselves can be destroyed by being engulfed by a larger one, in a process of cannibalism on an astronomical scale, or merge with another of similar size to form a new galaxy “, explains the author of the study.
The first compact galactic grouping was discovered in the 19th century; the so-called Stephan Quintet. Thanks to the large maps of the sky produced by various telescopes, such as the one at Mount Palomar, and more recently with the Sloan mapping, numerous of these groups have been discovered, all of them more or less close to Earth, up to a distance of one billion light years.
“Due to the time it takes for light to reach Earth, we have so far observed these galaxies as they were at most a billion years ago. This, while impressive time on a human scale, is relatively short compared to the age of the Earth. universe [about thirteen billion years] “, says the IAC researcher.
From the most distant compact galactic groups, however, it is difficult to obtain data, since the enormous distance at which they are found makes the galaxies appear as faint and small objects, even with large telescopes.
For this research, the Isaac Newton Telescope (INT) and the largest optical-infrared telescope in the world, the Gran Telescopio Canarias (GTC), both located at the Roque de los Muchachos Observatory, on the Canary island of La Palma, have been used. For Gutiérrez, “the great astronomical eye of the GTC is allowing in different astronomical disciplines a deep space survey unparalleled to date”.
The work shows that these very distant compact groups have properties similar to those of the current compact groups. However, the close position of the galaxies and the relative velocities between them seem to indicate that the lifetime of these structures is relatively short. On the contrary, the shape and types of stars that make up the member galaxies indicate that they are ancient galaxies, much older than the groups themselves.
The ephemeral life of these compact groups leads one to wonder about the final destination of these formations. A suggestive hypothesis is that all the galaxies of a compact group could end up included in a single giant galaxy, the result of their merger. Producing a complete picture of the entire process of formation and evolution of these structures will require observations of a greater number of objects that allow us to have significant statistical samples.
