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arXiv · 1205.5452

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

S. Alaghband-Zadeh·S. C. Chapman·A. M. Swinbank·Ian Smail·C. M. Harrison·D. M. Alexander·C. M. Casey·R. Dave·D. Narayanan·Y. Tamura·J. Umehata
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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.

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S. Alaghband-Zadeh, S. C. Chapman, A. M. Swinbank, Ian Smail, C. M. Harrison, D. M. Alexander, C. M. Casey, R. Dave, D. Narayanan, Y. Tamura, J. Umehata. 2012-05-24. Integral Field Spectroscopy of 2.0<z<2.7 Sub-mm Galaxies; gas morphologies and kinematics. https://doi.org/10.1111/j.1365-2966.2012.21386.x

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