AGN (Active Galactic Nuclei) feedback is a crucial topic in astrophysics. After more than two years of research and development, Prof. Feng Yuan and Prof. Suoqing Ji ’s group has successfully upgraded their existing 2D AGN feedback model platform, MACER, to a 3D simulation platform, MACER3D. This platform enables simulations from the boundary of the black hole accretion disk to the galaxy halo scale (~250 kpc), incorporating important physical processes such as cosmological inflows, AGN feedback, and stellar feedback. The establishment of this platform paves the way for further research on AGN feedback. This work was published in The Astrophysical Journal under the title “MACER3D — an upgrade of MACER2D with enhanced subgrid models and gas physics — and its application to simulating AGN feedback in a massive elliptical galaxy”. Ph.D. students Haoen Zhang and Haojie Xia from Shanghai Astronomical Observatory, Chinese Academy of Sciences, are co-first authors, while Prof. Suoqing Ji and Prof. Feng Yuan are co-corresponding authors.
Observations have revealed a strong correlation between the mass of supermassive black holes at the centers of galaxies and the properties of their host galaxies, suggesting that black holes and galaxies co-evolve. The physical mechanism behind this co-evolution is generally attributed to AGN feedback. Due to the complexity of this process, theoretical research primarily relies on numerical simulations, and current international simulations are mainly conducted at cosmological scales, with influential works such as IllustrisTNG and EAGLE. The advantage of this type of simulation is that it can provide a reliable environment for galaxy evolution, such as the gravitational potential of the galaxy. However, the disadvantages are also apparent: due to the low resolution, the simulation cannot accurately resolve small-scale physical processes. For example, the estimation of the black hole accretion rate, which is crucial for studying AGN feedback, can have an error of more than two orders of magnitude in cosmological simulations. In addition to the black hole accretion rate, the effects of AGN radiation, winds, and jets on the gas around the black hole are difficult to calculate accurately and require the adoption of some parameterized phenomenological methods.
In contrast to cosmological simulations, the research group led by the applicants has taken a different approach, focusing on high-resolution AGN feedback numerical simulations at the galaxy scale rather than the cosmological scale for many years. In 2018, they successfully developed the MACER model. Compared with cosmological simulations, MACER’s biggest advantage is its extremely high spatial resolution, which allows it to resolve the outer boundary of the accretion disk, thereby accurately calculating the black hole accretion rate. In addition, we can easily introduce more physically reliable AGN feedback models, which can accurately calculate various outputs of AGN and their interactions with galactic gas. The research group has applied the MACER model to a series of studies on AGN feedback and achieved significant results. However, the model is two-dimensional, and its axisymmetric assumption leads to disadvantages such as reverse cascade of turbulent energy and missing asymmetric structures. In addition, the basic code of the model - ZEUS - is relatively outdated.
The research team spent two years tackling challenges and built the MACER3D framework based on the new-generation fluid dynamics code Athena++, achieving a leap from 2D to 3D. This not only breaks through the bottleneck of exponentially increasing computational workload but also systematically incorporates cutting-edge achievements such as radiation cooling algorithms, supernova feedback, and multiphase turbulence into MACER3D. In addition, the framework has high scalability and can easily incorporate modules such as magnetic fields and cosmic rays in the future. The research group used MACER3D to simulate the evolution of elliptical galaxies, as shown in Figure 1. While verifying the previous MACER results, many interesting new results were discovered.
Link to the paper：https://iopscience.iop.org/article/10.3847/1538-4357/adcaba
Figure 1: Spatial distributions of gas number density, temperature, and radial velocity at different times and AGN luminosities in the simulated elliptical galaxy.