Project: dp134
Author: Ben Morton (
Team members: Prof. Sadegh Khochfar, Dr. Jose Onorbe

Dynamical friction is the process by which a massive perturber, moving through some

background medium, gravitationally interacts with that medium, producing a net retarding

force to its motion. When the background medium is gaseous, the pressure forces present in

the gas must be included in modelling the response of the medium, and so impact the

resultant force. We have run a high resolution, gravo-hydrodynamics zoom simulation of a

M~1E8 Msolar halo (at redshift z=10) embedded in a cosmological simulation box, using the

standard LambdaCDM cosmology, using the multi-physics simulation code GIZMO. We are in

the process of studying the impact of dynamical friction from dark matter substructure within

this host halo, looking specifically for the signal of density enhancement, which could

potentially trigger molecular hydrogen formation, and so spark early star formation. The

figure below shows an example of the density enhancement we might expect for such sub

structure, taken from idealised simulations of an extended perturber in a gaseous medium,

also using GIZMO.

Figure 1: Overdensity [top] in wake from extended perturber (Plummer sphere), moving at Mach 2,
produced using idealised tests using GIZMO. Analytic prediction from Ostriker 1999 shown in white.
Difference between numerical and analytic solution [bottom].
Categories: 2022 Highlights