Halo concentration strengthens dark matter constraints in galaxy-galaxy strong lensing analyses

Understand

A defining prediction of the cold dark matter (CDM) cosmological model is the existence of a very large population of low-mass haloes.

• This population is absent in models in which the dark matter particle is warm (WDM).
• These alternatives can, in principle, be distinguished observationally because halos along the line-of-sight can perturb galaxy-galaxy strong gravitational lenses.
• Furthermore, the WDM particle mass could be deduced because the cut-off in their halo mass function depends on the mass of the particle.