We present spatially resolved kinematics of 31 ALMA-identified dust-obscured
star-forming galaxies (DSFGs) at z∼1.3-2.6, as traced by Hα
emission using VLT/KMOS near-infrared integral field spectroscopy from our
on-going Large Programme ''KMOS-ALMA Observations of Submillimetre Sources''
(KAOSS). We derive Hα rotation curves and velocity dispersion profiles
for the DSFGs. Of the 31 sources with bright, spatially extended Hα
emission, 25 display rotation curves that are well fit by a Freeman disc model,
enabling us to measure a median inclination-corrected velocity at 2.2Rd of vrot = 190 ± 30 kms−1 and a median intrinsic velocity
dispersion of σ0 = 87 ± 6 kms−1 for these disc-like
sources. By comparison with less actively star-forming galaxies, KAOSS DSFGs
are both faster rotating and more turbulent, but have similar vrot/σ0 ratios, median 2.4 ± 0.5. We suggest that vrot/σ0 alone is insufficient to describe the kinematics of DSFGs, which
are not kinematically ''cold'' discs, and that the individual components
vrot and σ0 indicate that they are in fact turbulent, but
rotationally supported systems in ∼50 per cent of cases. This turbulence
may be driven by star formation or mergers/interactions. We estimate the
normalisation of the stellar Tully-Fisher relation (sTFR) for the disc-like
DSFGs and compare it with local studies, finding no evolution at fixed slope
between z∼2 and z∼0. Finally, we use kinematic estimates of DSFG halo
masses to investigate the stellar-to-halo mass relation, finding our sources to
be consistent with shock heating and strong feedback which likely drives the
declining stellar content in the most massive halos.Comment: 20 pages, 12 figures, submitted to MNRAS, updated author lis