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April 25, 202211:30 am – 12:30 pm (CDT)

A Dynamics-Based Density Profile for Dark Matter Halos


Benedikt Diemer (University of Maryland)


Jonelle Walsh



Mitchell Institute for Fundamental Physics & Astronomy

College Station, Texas 77843

Event Details

We now know that the density profiles of dark matter haloes carry signatures of their dynamical state and even of the nature of dark matter. Some of the most interesting signals reside at large radii (around the virial radius and beyond), which have recently become observationally accessible via satellite distributions and weak lensing. However, to harness the rapid progress promised by future instruments such as VRO/LSST and Roman, we need to significantly upgrade our theoretical understanding. One key roadblock has been the superposition of orbiting and infalling dark matter particles, which obscures the true shape of the orbiting (1-halo) term at large radii. Based on a novel algorithm to split simulated halos into their dynamical components, I introduce a new fitting function for profiles out to large radii that accurately describes the orbiting and infalling terms. I show that the best-fit parameters are systematically related to the halo properties of interest, providing a new framework for interpreting both simulated and observed profiles.

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