Cutting-edge technology has been used to investigate theories about the evolution of galaxies.
A spectacular trio of merging galaxies, named by astronomers as SDSSCGB 10189. (Images courtesy of ESA/Hubble and NASA, M. Sun)
New Delhi: Astronomers believe that most large galaxies, like the Milky Way, formed through a series of interactions with smaller galaxies. Deep space observatories such as the James Webb Space Telescope and the Hubble Space Telescope frequently observe galaxies in the process of merging, showing how the gravitational influence of all the interacting galaxies redistributes clouds of gas and dust, promoting the formation of new stars. Astronomers have traced the Milky Way's past by carefully studying the chemical composition and orbits of the stellar populations within our own galaxy, all the way back to the ancient galaxies that were absorbed into the Milky Way.
“Stephen's Quintet” shows in exquisite detail how galaxy mergers drive star formation. (Images credit: NASA, ESA, CSA, STScI)
However, astronomers have not previously understood much about the historical past of other galaxies. The researchers trained a machine learning algorithm on a simulation of galaxy formation and then traced the formation and evolutionary history of 10,000 galaxies close to our own. This work allowed the scientists to investigate different theories of star formation. The scientists found that only 20 percent of the galaxy's stars were formed by past mergers. This indicates that while mergers play an important role, they are not the main source of new stars in galaxies.
Dark matter halos reveal galaxy mergers
The study also showed that larger and more massive galaxies are more susceptible to mergers. In such galaxies, 35-40% of stars formed through mergers. Old elliptical galaxies and dead galaxies that are not forming new stars have a higher percentage of stars born within them than spiral galaxies where star formation is ongoing. Galaxies with more mergers have more massive dark matter halos, indicating that the cosmic environment influences the merger history of galaxies.
Illustration of the Milky Way surrounded by a blue dark matter halo. (Image credit: ESO/L. Calçada)
A paper describing the results of the research has been published. Natural Astronomy“The ability to investigate the merger history of galaxies could help us to better understand how galaxies form and evolve. For example, we could find out whether mergers contribute to the formation of certain types of galaxies, or whether they initiate important processes such as intense bursts of star formation or enhanced activity in active galactic nuclei,” said Eirini Angeloudi, lead author of the study. The researchers plan to apply the same technique to more distant galaxies.
