Dark matter content of star-forming galaxies at Cosmic Noon: 100 individual, high-resolution rotation curves at redshifts 0.6-2.5

The evolution of galaxies is strongly related to the Dark matter halos in which they reside, and these halos play a key role in determining the dynamics and structure of the galaxy it hosts. Using high-resolution observations of Ha and CO emission lines observed with the VLT (KMOS & SINFONI) and NOEMA, we sample 100 star-forming galaxies at z=0.6-2.5 along the SFR main sequence, with masses ranging between log(Mstar)=9.6-11.4. Their rotation curves extend beyond the effective radius (median 2Re) and thus probe the region gravitationally dominated by the dark matter. Using a mass model consisting of a: (i) thick turbulent disk, (ii) central stellar bulge and (iii) an NFW dark matter halo we model each of the rotation curves, corrected for beam-smearing and asymmetric drift (using DysmalPy). At z~2, half of all galaxies are baryon-dominated, with 28% (N=19) galaxies having a dark-to-total mass fraction of < 0.1. In general, dark matter fractions decrease with redshift and we find the fitting function 0.75*(1+z)^-1.07 to be a good fit. Compared to the dark matter content predicted by cosmological simulations, assuming an NFW profile such low dark matter fractions translate to a deficit of ~40% in mass. To match the virial mass suggested by scaling relations, and keeping the low dark matter content on the galaxy scale, we invoking a "core" (ρ~r^0) instead of "cuspy" (ρ~r^-1) NFW profile in the inner halo. The very low dark matter fractions are explained naturally for a cored profile. The redistributing of dark matter to the outer parts of the halo can be driven by a combination of rapid bulge growth, with strong AGN feedback processes, as suggested by recent analytical models.