Interacting Galaxies in the IllustrisTNG Cosmological Simulations

Abstract:

Observational studies of galaxy pairs have shown that galaxy-galaxy interactions can alter numerous galaxies properties, such as star formation rates, active galactic nuclei (AGN) fractions and gas-phase metallicities.  These effects have been predicted using idealized binary merger simulations, and can be attributed to inflows of gas that are triggered by gravitational and hydrodynamical interactions between the galaxies. Cosmological simulations provide an opportunity to see how changes in the properties of interacting galaxies arise within a cosmological context, with galaxy pairs spanning a wide range of masses, mass ratios, gas content, environments and orbits. 

We have constructed several large, well-defined samples of interacting galaxies in the IllustrisTNG cosmological hydrodynamical simulations (TNG50, TNG100 and TNG300), along with control galaxies that are matched in stellar mass, redshift, local density and isolation. We find clear evidence of enhanced star formation rates in IllustrisTNG galaxy pairs, with the level and radial extent of these enhancements being consistent with those seen in galaxy pairs selected from the Sloan Digital Sky Survey.  By reconstructing the orbits of interacting galaxies in the TNG100 simulations, we find that close encounters trigger these enhancements, primarily via increased star formation efficiency rather than increased gas supply.  These reconstructed orbits have also yielded new insights in the prevalence and timescales of close encounters and mergers.

Bio:

My primary research interests lie in the study of galaxy evolution, with a particular focus on the role of galaxy-galaxy interactions and mergers. 

My collaborators and I have published an extensive series of articles on close galaxy pairs and post-merger galaxies in the Sloan Digital Sky Survey, beginning with Ellison et al. (2008).  As a core member of this collaboration, I have led studies on galaxy colours (Patton et al. 2011), star formation rates (Patton et al. 2013) and asymmetries (Patton et al. 2016).  We have also used idealized merger simulations (e.g. Patton et al. 2013, Moreno et al. 2015, Moreno et al. 2021) to better understand the trends we have seen in observations.  More recently, we have extended this line of research to cosmological simulations (especially IllustrisTNG), enabling a more direct comparison between observations and simulations of galaxy pairs (Patton et al. 2020) and post-mergers (Hani et al. 2020).

Learn More:

• About galaxy pairs: https://www.sciencedirect.com/topics/physics-and-astronomy/galaxy-pairs
• About Cosmological simulations of galaxy formation: https://www.nature.com/articles/s42254-019-0127-2
• See his Trent University webpages here: https://dpatton.trentu-physics-astronomy.ca/
• Read this article, "Trent Prof Part of International Research Team that Makes Galactic Discovery" here