How Galaxy Collisions Shape the Universe
In a study led by Mauro D’Onofrio’, researchers investigated how galaxy collisions—known as dry mergers—affect the structural properties of galaxies, often represented through scaling relations. These relationships include connections between brightness, size, mass, and other features of galaxies. Scaling relations help astronomers understand the physical processes behind galaxy formation and evolution over time. The team explored these phenomena by comparing observational data and advanced computer simulations to develop a simplified model of galaxy mergers.
Background
Galaxies evolve through complex processes, including star formation, collisions, and the influence of gravity. This research focused on dry mergers, which are collisions where little to no new stars form. Unlike more active mergers, these events predominantly alter the structure and dynamics of galaxies without significant bursts of light from new stars.
Methods
The researchers analyzed galaxy data from three major surveys: WINGS (focusing on nearby clusters), MaNGA (mapping nearby galaxies), and LEGA-C (observing high-redshift galaxies). These datasets provided diverse snapshots of galaxy properties, including size, brightness, and velocity. To compare these observations with theoretical predictions, they examined two advanced simulations: EAGLE and Illustris-TNG, which model galaxy evolution in a cosmic context.
A key part of the study involved creating a simplified mathematical model to simulate the effects of dry mergers. This model allowed the researchers to predict how galaxy properties, such as size and velocity, change after repeated mergers.
Key Findings
Scaling Relations Over Time
The simplified model successfully reproduced many features observed in galaxy scaling relations, such as patterns in brightness versus size and mass versus velocity. These patterns align closely with observations and complex simulations, supporting the idea that dry mergers play a major role in galaxy evolution.
Simulation Comparisons
Both EAGLE and Illustris-TNG simulations accurately captured large-scale trends in galaxy properties, including the distinctive shapes of their distributions. However, differences emerged in the finer details, such as the scatter and slopes in specific relationships.
Evolution Across Time
The study found that galaxy size and brightness evolve differently depending on their mass. Larger galaxies grow steadily over time, while smaller ones experience minimal changes in size. This suggests that dry mergers significantly impact the growth of massive galaxies but play a lesser role in smaller systems.
Conclusion
This research highlights the importance of dry mergers in shaping the observable properties of galaxies. By combining data from surveys, detailed simulations, and simplified mathematical models, D’Onofrio’ and his team provided a clearer understanding of how galaxies change over time. Their findings confirm that mergers are a driving force behind the scaling relations seen in galaxies today, offering valuable insights into the history of the universe.
Source: D’Onofrio’
