Integral Field Spectroscopy of 2.0<z<2.7 Sub-mm Galaxies; gas morphologies and kinematics

TL;DR

This study uses integral field spectroscopy to analyze gas morphologies and kinematics in nine high-redshift sub-mm galaxies, revealing merger-driven dynamics, high star formation rates, and consistency with star formation laws.

Contribution

It provides detailed gas morphology and kinematic data for a sample of SMGs, highlighting their merger nature and estimating their halo masses, which advances understanding of galaxy evolution at high redshift.

Findings

SMGs show high velocity dispersions (~220 km/s) and large half-light radii (~3.7 kpc).

Major mergers are prevalent among SMGs, with distinct multiple components and velocity offsets.

SMGs have star formation rates around 370 solar masses per year, twice that of quiescent galaxies at similar redshift.

Abstract

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 Halpha velocity dispersion of sigma=220+-80km/s and an average half light radius of r=3.7+-0.8kpc. The average dynamical measure, V_obs/2sigma=0.9+-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 SMGs' far-infrared SFRs, measured using Herschel-SPIRE far-infrared photometry, are on average 370+-90Mo/yr which is ~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+-100km/s and average projected spatial offsets of 8+-2kpc, 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 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 Halpha components with sub-halo offsets in the Millennium simulation database we infer an average halo mass for SMGs of 13<log(M[h^-1Mo])<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.