New data on the interaction between galaxies in galactic pairs

(ORDO NEWS) — The merger of galaxies is one of the important stages in the evolution of galaxies, and yet, the percentage of galactic pairs from the total number of all galaxies and the influence of pair coexistence on their physical properties remain rather conditionally determined.

A new study led by a team led by Professor Y. Sophia Dai of the South American Astronomical Center of the Chinese Academy of Sciences presents new results showing how the interaction between two galaxies influences their formation and evolution.

“From an archive of 6 years of grism spectroscopic observations conducted with the Hubble Space Telescope (“Hubble”), we were able to select spectra for more than 413 pair systems that include two or more galaxies, thus confirming the presence of an interaction between them.”

Grim spectroscopic observations carried out with the Hubble telescope make it possible to take the spectra of cosmic sources in the near infrared range, and this makes it possible to detect galaxies in the distant Universe, as well as to obtain kinematic confirmation of the pair coexistence of galaxies, accurately measuring their small spectroscopic redshifts (then there are radial velocities).

Using this unprecedented data, Professor Dai and her team have built the largest set of emission line galaxies to a depth of 7 billion years.

After studying the resulting model, the scientists found that during the interaction between two galaxies, an increase in the rate of star formation by 40-60 percent is observed, which indicates an acceleration in the growth of the galaxies that make up the pair. This level of acceleration of star formation processes is characteristic of the local Universe, including a similar increase in the rate of star formation due to the interaction between galaxies.

It is interesting to note that despite the increase in the rate of star formation, the activity in the center of the galaxy (in the vicinity of supermassive black holes) changed little as a result of the interaction. In fact, the percentage of galaxies with the most actively growing black holes, often called active galactic nuclei, turned out to be about the same for both pair and single emission line galaxies.

The researchers imposed a limit on the proportion of galaxies that are part of galactic pairs – if you move back in time, then in the Universe an increasing number of galaxies are found in pairs. This dependence is approximated by a power function with a relatively small exponent equal to about 0.6, the authors noted.

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