ASP Online Seminars: The Density of Dark Matter in the Centres of Galaxies

by Prof. Amr El-Zant (The British University, Egypt)

Tuesday 19 May 2026, 13:00 → 14:30 UTC

Abstract:

Barring modifications to fundamental physical law, most of the matter in our universe is dark. It manifests itself in terms of gravitational signatures, such as the rotation speeds of stars and gas in the outer parts of galaxies. Through the past four decades, a standard cosmological model has materialized, in the context of which galaxies reside in ‘haloes’ of cold dark matter. The model makes definite predictions regarding the density profile of those haloes; although the resulting mass distribution is consistent with the outer rotation curves, there appears to be too much dark mass in the central regions — that is, solving the outer missing mass problem has led to an excess in the centre. This so called ‘cusp/core’ problem constitutes a challenge to our current models of galaxy formation in a cosmological context, and perhaps to the cosmological model itself.  After reviewing essential background, I will discuss the current status of the cusp/core problem and some of the solutions proffered — from those invoking fundamental modifications of the standard cold dark matter scenario to those involving the details of the ‘gastrophysics’ of galaxy formation — focusing on models developed with collaborators through the years.

 

Bio of the speaker:

Prof. Amr El-Zant is a theoretical astrophysicist interested in the formation and evolution of galaxies and physical cosmology.  He obtained his DPhil from the University of Sussex in 1997 under R. J. Tayler (FRS) and held research positions in international institutes, including the California Institute of Technology (Caltech) and the Canadian Institute for Theoretical Astrophysics (CITA, U. Toronto, where he was also an honorary Senior Fellow at Massey College). In Egypt, he was associate professor at Zewail City of Science and Technology before becoming director of the Centre for Theoretical Physics at The British University in Egypt (in 2013).