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Notoriously difficult to constrain with observations and physically intricate to model in simulations, the non-thermal physics of cosmic rays (CRs) and magnetic fields (B-fields), and their effects on galaxies, remain mostly elusive. The study of these processes is timely and scientifically exigent. Current simulations are able to evolve CRs with magnetic fields in tandem with feedback from stars, black holes (AGNs), and other fluid microphysics (e.g., thermal conduction, viscosity). However, one of the key emergent parameters of CR transport, the diffusivity, still remains largely unconstrained. In this talk, I will review our current understanding of the physics of CRs and B-fields and pre-existing observational constraints, and then discuss recent results from the state-of-the-art Feedback in Realistic Environments (FIRE) zoom-in galaxy simulations on showing the impact of CRs on galaxies and CGM gas. Next, I will discuss how observational constraints such as X-ray emission and the tSZ effect can be used to place constraints on their transport models. I will reinforce the importance of including such non-thermal processes in our galaxy formation recipes and propose future studies for further constraining the models.

BIO

Although born elsewhere and later moving to Northern America, Samuel Lu spent the majority of his formative years growing up in Beijing. He obtained his bachelor’s degrees in physics and mathematics, with a minor in astronomy, from the University of California, Santa Barbara in 2022, and is currently a PhD candidate in physics at the University of California, San Diego. He is mostly interested in galaxy formation and evolution, with a particular focus on the non-thermal processes. He is part of the Feedback in Realistic Environments (FIRE) simulation project, where his main collaborators are Dusan Keres, Phil Hopkins, and Sam Ponnada. One of the main goals of the expedition of FIRE (especially FIRE-2 and 3) is to explore some of the physical mechanisms in galaxy formation that seem to be "secondary" compared to stellar and AGN feedback, such as CRs, MHD, and dust. However, more and more works have shown that although these non-thermal processes may be unimportant in matching empirical constraints, they nonetheless affect both the dynamics and observables of the galaxy and CGM. Our work aims to reveal such connections and provide aspects for new-era galaxy simulations.

Host： Hui Li