(Galaxies are not generally found in isolation. Most are surrounded by a swarm of satellite galaxies and are themselves embedded in larger aggregates called groups or clusters. Galaxies that possess no nearby, luminous neighbors (though they may be accompanied by small satellites) are classified as isolated galaxies.)
A team of researchers led by Anderson Caproni has published a study in which they explore the impact of boundary conditions on the gas removal process in isolated galaxies. The study focuses on three-dimensional hydrodynamic simulations aimed at studying the evolution of the gas content in isolated galaxies and its connection with the galactic history of star formation.
The simulations were performed using different boundary conditions: open, closed, and selective boundary conditions. The open boundary condition was discovered to break the previous monotonic trend due to the rise of strong matter inflows, resulting in extremely high masses in comparison to what would be expected for a dwarf galaxy. The researchers conclude that a computational domain with a size of 6 kpc is enough to minimise boundary effects on the gas losses in similar simulations performed in this study.
The study found that open boundaries with sizes smaller than approximately 10 times the characteristic radius of the galactic dark-matter halo become inappropriate for this kind of simulation after about 0.6 Gyr of evolution since they act as an infinite reservoir of gas due to dark-matter gravity. The researchers also tested two different boundary conditions that avoid gas accretion from numerical frontiers and found that the selective boundary condition (that uses a velocity threshold criterion to open or close frontiers) is preferable as it minimizes the number of reversed shocks due to closed boundaries.
This study has important implications for the field of astrophysics and the understanding of isolated galaxies. The results show that simulations with selective boundary conditions can produce results that are comparable to those obtained with larger computational domains but at a lower computational cost. The findings of this study will be valuable for future simulations of isolated galaxies and the evolution of their gas content.
In conclusion, Anderson Caproni and his team have made significant contributions to our understanding of the impact of boundary conditions on the gas removal process in hydrodynamic simulations of isolated galaxies. The results of this study will be of great interest to the astrophysics community and will pave the way for further research in this field.
Source: Caproni, Anderson et al. “Boundary Conditions in Hydrodynamic Simulations of Isolated Galaxies and Their Impact on the Gas-loss Processes.” The Astrophysical Journal 944 (2023): n. pag. https://doi.org/10.48550/arXiv.2302.04825