Willem Kroese & Julius Hendrix investigated the evolution of red-to-blue galaxies in the EAGLE simulations

Willem Kroese (left) and Julius Hendrix (right), bachelor students at Leiden University

Willem Kroese and Julius Hendrix have recently completed the bachelor research project at Leiden University. I have had the pleasure to be Willem & Julius’ main supervisor. The students investigated the physical origin of rejuvenation in galaxies using the EAGLE cosmological hydrodynamical simulations.

Rejuvenated galaxies are defined as galaxies that move from the red sequence onto the blue cloud. This behaviour is poorly understood and few cases have ever been observed. The EAGLE simulations are able to model rejuvenated galaxies on a large scale, making further research into their behaviour possible. Willem & Julius tracked the intrinsic u-r colour of galaxies, and found that rejuvenation in galaxies is not uncommon. 11% of central and 6% of satellite galaxies with masses above 10^10 M⊙ show some form of rejuvenation. Looking at the evolution of this rejuvenating sample reveals that rejuvenators generally are massive and elliptical in shape. They are also slightly more extended in size compared to galaxies with similar masses.

Willem & Julius made visualisations of these galaxies, and found that most central rejuvenator galaxies undergo minor or major merger events, and minor interactions with satellite galaxies before rejuvenation. Satellite rejuvenators show steady mass accretion and minor interactions before exhibiting rejuvenative behaviour. Rejuvenation seems more common in central galaxies because of the higher chance of interactions with other galaxies.

The students work will be published soon. Stay tuned!

Congratulations Willem! Congratulations Julius!