Rotation Curves in z~1-2 Star-Forming Disks: Evidence for Cored Dark Matter Distributions

TL;DR

This study presents high-quality rotation curves of massive star-forming galaxies at z~1-2, revealing that many have cored dark matter profiles with less dark matter than expected from standard models, suggesting baryonic processes reshape dark matter distributions.

Contribution

First detailed rotation curves for large, massive SFGs at z~1-2 showing evidence for cored dark matter distributions, challenging the standard NFW profile assumptions.

Findings

Most z>1.2 SFGs are baryon dominated within a few Re.

Dark matter fractions are lower than maximal disks, especially at higher redshifts.

Evidence suggests dark matter cores formed due to baryonic processes like feedback and radial baryon transport.

Abstract

We report high quality, Halpha or CO rotation curves (RCs) to several Re for 41 large, massive, star-forming disk galaxies (SFGs), across the peak of cosmic galaxy evolution (z~0.67-2.45), taken with the ESO-VLT, the LBT and IRAM-NOEMA. Most RC41 SFGs have reflection symmetric RCs plausibly described by equilibrium dynamics. We fit the major axis position-velocity cuts with beam-convolved, forward modeling with a bulge, a turbulent rotating disk, and a dark matter (DM) halo. We include priors for stellar and molecular gas masses, optical light effective radii and inclinations, and DM masses from abundance matching scaling relations. Two-thirds or more of the z>1.2 SFGs are baryon dominated within a few Re of typically 5.5 kpc, and have DM fractions less than maximal disks (<fDM (Re)>=0.12). At lower redshift (z<1.2) that fraction is less than one-third. DM fractions correlate inversely with the baryonic angular momentum parameter, baryonic surface density and bulge mass. Inferred low DM fractions cannot apply to the entire disk & halo but more plausibly reflect a flattened, or cored, inner DM density distribution. The typical central 'DM deficit' in these cores relative to NFW distributions is ~30% of the bulge mass. The observations are consistent with rapid radial transport of baryons in the first generation massive gas rich halos forming globally gravitationally unstable disks, and leading to efficient build-up of massive bulges and central black holes. A combination of heating due to dynamical friction and AGN feedback may drive DM out of the initial cusps.