Cosmic ray feedback and constraints on cosmic ray propagation

Cosmic rays (CRs) are energetic charged particles originating outside the Earth. They could have strong effects on galaxy evolution, which we are going to study with galaxy simulations.

We have successfully implemented CRs and CR feedback in GIZMO. We model CRs with a two fluid models (gas+CRs) with diffusion and streaming.

I have given a talk in the 2018 Santa Cruz galaxy workshop:

The slide is available here: TsangKeungChan_CRdrivenwind

I have also worked on simulating pionic gamma ray emission from cosmic rays, which can be seen in the poster ( Poster_CR_A0) I presented in the 15th Potsdam Thinkshop.

 

Here are some cool movies featuring cosmic ray feedback on different galaxies!

Images are weighted by mass times temperature, so higher temperature gas (>10^3K) is more visible.

The movie below shows idealized dwarf galaxies with (left) and without cosmic rays (right) (with isotropic diffusion coefficient 3e28cm^2/s). Surprisingly, cosmic rays allow more cold gas (magenta) to stay within the disks.

MW-mass galaxies with (left) and without cosmic rays (right). There is significant fast outflowing hot gas on the left but warm slow outflowing gas on the right at late times:

Starburst galaxies with (right) and without (left) cosmic ray (diffusion coefficient=3e28cm^2/s):