SANTA CRUZ DE TENERIFE, 22 Jul. (EUROPA PRESS) –
An investigation led by the Instituto de Astrofísica de Canarias (IAC) has utilised an innovative method based on artificial intelligence to examine the formation of stars in galaxies. Through the analysis of 10,000 neighbouring galaxies, it has been revealed that the majority of stars are born within the boundaries of their own galaxy. While galactic mergers are significant, they are not the primary source of new stars. Moreover, the study indicates that the most massive galaxies are more impacted by these mergers. These findings, published in ‘Nature Astronomy’, offer fresh insights into the intricate history of galaxies and their evolution over time.
The majority of galaxies do not exist in solitude but rather merge with others due to gravitational forces. These mergers profoundly transform galaxies, altering their mass, size, shape, and even their internal composition. However, mere observations are insufficient to precisely ascertain the number of mergers a galaxy has undergone in the past and whether these involved galaxies of comparable sizes or vastly different ones.
Disparities in the orbits and chemical compositions of stars in the Milky Way suggest diverse cosmic origins, providing clues about the history of galaxy mergers. Yet, the quantity of stars originating from mergers has only been gauged in a small fraction of external galaxies, underscoring the dearth of comprehensive studies on the impact of mergers across a representative galaxy sample.
Cosmological simulations enable the observation of how galaxies evolve throughout the universe’s history, divulging details beyond the reach of telescopes. Conversely, artificial intelligence (AI) excels in unveiling concealed patterns within vast datasets. By synergising these potent tools, scientific teams are formulating AI models trained on simulated galaxies capable of analysing real galaxies, predicting their attributes, and reconstructing their cosmic chronicles. This fusion of simulations and AI marks a notable leap in our capacity to scrutinise the universe.
Adopting this approach, a team from the IAC has scrutinised 10,000 neighbouring galaxies to determine the proportion of stars formed through mergers with other galaxies. The research has disclosed that a mere 20 percent of the stellar mass in present galaxies stems from past mergers, indicating that the majority of stars in the current Universe originated internally.
While low-mass galaxies predominantly form stars internally, the most massive galaxies acquire up to 35 to 40 percent of their stellar mass through mergers. Thus, mergers exert a more profound influence on more massive galaxies compared to their lesser counterparts. Similarly, aging elliptical galaxies that no longer foster star formation appear to have accumulated more stars through mergers than their spiral counterparts that are still forming stars.
The study also indicates that galaxies at the core of denser dark matter halos tend to have encountered more mergers than those situated within less dense halos, hinting that a galaxy’s cosmic milieu can influence its history of interactions.
“The ability to delve into the history of galaxy mergers could enhance our comprehension of how galaxies take form and evolve,” explains Eirini Angeloudi, a PhD candidate at the IAC spearheading the study. “For instance, we can probe whether mergers contribute to the formation of specific galaxy types or trigger pivotal processes, such as intense bursts of star formation or heightened activity in Active Galactic Nuclei,” she adds.
“Our research demonstrates how cosmological simulations and machine learning can be amalgamated to furnish a tool for extracting insights into the cosmic past of contemporary galaxies. This approach could be extended to construct complete galaxy merger lineages,” mentions Marc Huertas, a researcher at the IAC and co-author of the study.
NEXT CHALLENGE: EXPLORING FURTHER GALAXIES
Despite the promising findings, the team cautions that the simulations utilised to unravel the Universe are confined by current knowledge. This implies they may contain inaccuracies and errors, particularly when attempting to comprehend intricate phenomena on a minute scale.
“While we have identified associations between a galaxy’s properties and the impact of mergers on its stellar mass, correlation does not always imply causality,” notes Jesús Falcón, an IAC researcher involved in the study, further stating: “Thus, we cannot definitively assert whether mergers are the primary factors underpinning the various observed processes in neighbouring galaxies, such as morphological alterations or the cessation of star formation.”
The team plans to expand the study to distant galaxies as a subsequent step, enabling them to monitor the evolution of mergers and evaluate their contribution to a galaxy’s stellar mass at different stages of the Universe’s evolution. “These advancements would furnish insights into how galactic mergers influence the progression of galaxies across cosmic epochs, illuminating their role in shaping the spectrum of galactic structures and properties witnessed today,” concludes Angeloudi.
