The `core-cusp' problem is considered a key challenge to the LCDM paradigm.
Halos in dark matter only simulations exhibit `cuspy' profiles, where density
continuously increases towards the centre. However, the dark matter profiles of
many observed galaxies (particularly in the dwarf regime) deviate strongly from
this prediction, with much flatter central regions (`cores'). We use NewHorizon
(NH), a hydrodynamical cosmological simulation, to investigate core formation,
using a statistically significant number of galaxies in a cosmological volume.
Halos containing galaxies in the upper (M* > 10^10.2 MSun) and lower (M* < 10^8
MSun) ends of the stellar mass distribution contain cusps. However, halos
containing galaxies with intermediate (10^8 MSun < M* < 10^10.2 MSun) stellar
masses are generally cored, with typical halo masses between 10^10.2 MSun and
10^11.5 MSun. Cores form through supernova-driven gas removal from halo
centres, which alters the central gravitational potential, inducing dark matter
to migrate to larger radii. While all massive (M* > 10^9.5 MSun) galaxies
undergo a cored-phase, in some cases cores can be removed and cusps reformed.
This happens if a galaxy undergoes sustained star formation at high redshift,
which results in stars (which, unlike the gas, cannot be removed by baryonic
feedback) dominating the central gravitational potential. After cosmic star
formation peaks, the number of cores, and the mass of the halos they are formed
in, remain constant, indicating that cores are being routinely formed over
cosmic time after a threshold halo mass is reached. The existence of cores is,
therefore, not in tension with the standard paradigm.Comment: 13 pages, 11 figures, Accepted to MNRA