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Durham University

Department of Physics

Staff profile

Publication details for Professor Ian Smail

Thomson, A. P., Simpson, J. M., Smail, Ian, Swinbank, A. M., Best, P. N., Sobral, D., Geach, J. E., Ibar, E. & Johnson, H. L. (2017). Evolution of Dust-obscured Star Formation and Gas to z = 2.2 from HiZELS. The Astrophysical Journal 838(2): 119.

Author(s) from Durham

Abstract

We investigate the far-infrared properties of galaxies selected via deep, narrow-band imaging of the Hα emission line in four redshift slices from z=0.40--2.23 over ∼1deg2 as part of the High-redshift Emission Line Survey (HiZELS). We use a stacking approach in the Herschel PACS/SPIRE bands, along with 850μm imaging from SCUBA-2 to study the evolution of the dust properties of Hα-emitters selected above an evolving characteristic luminosity threshold, 0.2L⋆Hα(z). We investigate the relationship between the dust temperatures and the far-infrared luminosities of our stacked samples, finding that Hα-selection identifies cold, low-LIR galaxies (Tdust∼14k; log[LIR/L⊙]∼9.9) at z=0.40, and more luminous, warmer systems (Tdust∼34k; log[LIR/L⊙]∼11.5) at z=2.23. Using a modified greybody model, we estimate "characteristic sizes" for the dust-emitting regions of HiZELS galaxies of ∼0.5kpc, nearly an order of magnitude smaller than their stellar continuum sizes, which may provide indirect evidence of clumpy ISM structure. Lastly, we measure the dust masses from our far-IR SEDs along with metallicity-dependent gas-to-dust ratios (δGDR) to measure typical molecular gas masses of ∼1010M⊙ for these bright Hα-emitters. The gas depletion timescales are shorter than the Hubble time at each redshift, suggesting probable replenishment of their gas reservoirs from the intergalactic medium. Based on the number density of Hα-selected galaxies, we find that typical star-forming galaxies brighter than 0.2L⋆Hα(z) host a significant fraction (35±10%) of the total gas content of the Universe, consistent with the predictions of the latest cosmological simulations.