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Durham University

Department of Physics

Staff profile

Publication details for Professor Ian Smail

Gullberg, B., Swinbank, A. M., Smail, I., Biggs, A. D., Bertoldi, F., Breuck, C. De, Chapman, S. C., Chen, C.-C., Cooke, E. A., Coppin, K. E. K., Cox, P., Dannerbauer, H., Dunlop, J. S., Edge, A. C., Farrah, D., Geach, J. E., Greve, T. R., Hodge, J., Ibar, E., Ivison, R. J., Karim, A., Schinnerer, E., Scott, D., Simpson, J. M., Stach, S. M., Thomson, A. P., van der Werf, P., Walter, F., Wardlow, J. L. & Weiss, A. (2018). The Dust and [C ii] Morphologies of Redshift ∼4.5 Sub-millimeter Galaxies at ∼200 pc Resolution: The Absence of Large Clumps in the Interstellar Medium at High-redshift. The Astrophysical Journal 859(1): 12.

Author(s) from Durham


We present deep, high-resolution (0 03, 200 pc) ALMA Band 7 observations covering the dust continuum and


λ157.7 μm emission in four z ∼ 4.4–4.8 sub-millimeter galaxies (SMGs) selected from the ALESS and
AS2UDS surveys. The data show that the rest-frame 160 μm (observed 345 GHz) dust emission is consistent
with smooth morphologies on kpc scales for three of the sources. One source, UDS 47.0, displays apparent
substructure, but this is also consistent with a smooth morphology—as indicated by simulations showing that
smooth exponential disks can appear clumpy when observed at the high angular resolution (0 03) and depth of
these observations (s345 GHz ~ 27 47 – μJy beam−1
). The four SMGs are bright [C II] emitters. We extract [C II]
spectra from the high-resolution data, and recover ∼20%–100% of the [C II] flux and ∼40%–80% of the dust
continuum emission, compared to the previous lower-resolution observations. When tapered to 0 2 resolution,
our maps recover ∼80%–100% of the continuum emission, indicating that ∼60% of the emission is resolved out
on ∼200 pc scales. We find that the [C II] emission in high-redshift galaxies is more spatially extended than the
rest-frame 160 μm dust continuum by a factor of 1.6 ± 0.4. By considering the L[ ] C II /LFIR ratio as a function of
the star formation rate surface density (SSFR), we revisit the [C II] deficit and suggest that the decline in the
L[ ] C II /LFIR ratio as a function of SSFR is consistent with local processes. We also explore the physical drivers
that may be responsible for these trends and can give rise to the properties found in the densest regions
of SMGs.