We present two-dimensional , integral field spectroscopy covering the rest-frame wavelengths of strong optical emission lines in nine sub-mm-luminous galaxies ( SMGs ) at 2.0 < z < 2.7 .
The GEMINI-NIFS and VLT-SINFONI imaging spectroscopy allows the mapping of the gas morphologies and dynamics within the sources , and we measure an average H \alpha velocity dispersion of \langle \sigma \rangle = 220 \pm 80 kms ^ { -1 } and an average half light radius of \langle r _ { 1 / 2 } \rangle = 3.7 \pm 0.8 kpc .
The dynamical measure , \langle V _ { obs } / 2 \sigma \rangle = 0.9 \pm 0.1 for the SMGs , is higher than in more quiescent star-forming galaxies at the same redshift , highlighting a difference in the dynamics of the two populations .
The far-infrared SFRs of the SMGs , measured using Herschel -SPIRE Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA . far-infrared photometry , are on average 370 \pm 90 M _ { \odot } yr ^ { -1 } which is \sim 2 times higher than the extinction corrected SFRs of the more quiescent star-forming galaxies .
Six of the SMGs in our sample show strong evidence for kinematically distinct multiple components with average velocity offsets of 200 \pm 100 kms ^ { -1 } and average projected spatial offsets of 8 \pm 2 kpc , which we attribute to systems in the early stages of major mergers .
Indeed all SMGs are classified as mergers from a kinemetry analysis of the velocity and dispersion field asymmetry .
We bring together our sample with the seven other SMGs with IFU observations to describe the ionized gas morphologies and kinematics in a sample of 16 SMGs .
By comparing the velocity and spatial offsets of the SMG H \alpha components with sub-halo offsets in the Millennium simulation database we infer an average halo mass for SMGs in the range of 13 < log ( M [ h ^ { -1 } M _ { \odot } ] ) < 14 .
Finally we explore the relationship between the velocity dispersion and star formation intensity within the SMGs , finding the gas motions are consistent with the Kennicutt-Schmidt law and a range of extinction corrections , although might also be driven by the tidal torques from merging or even the star formation itself .