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ALMA reveals potential evidence for spiral arms, bars, and rings in high-redshift submillimeter galaxies.

Hodge, J. A. and Smail, I. and Walter, F. and Cunha, E. da and Swinbank, A. M. and Rybak, M. and Venemans, B. and Brandt, W. N. and Rivera, G. Calistro and Chapman, S. C. and Chen, Chian-Chou and Cox, P. and Dannerbauer, H. and Decarli, R. and Greve, T. R. and Knudsen, K. K. and Menten, K. M. and Schinnerer, E. and Simpson, J. M. and Werf, P. van der and Wardlow, J. L. and Weiss, A. (2019) 'ALMA reveals potential evidence for spiral arms, bars, and rings in high-redshift submillimeter galaxies.', Astrophysical journal., 876 (2). p. 130.


We present subkiloparsec-scale mapping of the 870 μm ALMA continuum emission in six luminous (L IR ~ 5 × 1012 L ⊙) submillimeter galaxies (SMGs) from the ALESS survey of the Extended Chandra Deep Field South. Our high-fidelity 0farcs07-resolution imaging (~500 pc) reveals robust evidence for structures with deconvolved sizes of lesssim0.5–1 kpc embedded within (dominant) exponential dust disks. The large-scale morphologies of the structures within some of the galaxies show clear curvature and/or clump-like structures bracketing elongated nuclear emission, suggestive of bars, star-forming rings, and spiral arms. In this interpretation, the ratio of the "ring" and "bar" radii (1.9 ± 0.3) agrees with that measured for such features in local galaxies. These potential spiral/ring/bar structures would be consistent with the idea of tidal disturbances, with their detailed properties implying flat inner rotation curves and Toomre-unstable disks (Q < 1). The inferred one-dimensional velocity dispersions (σ r lesssim 70–160 km s−1) are marginally consistent with the limits implied if the sizes of the largest structures are comparable to the Jeans length. We create maps of the star formation rate density (ΣSFR) on ~500 pc scales and show that the SMGs are able to sustain a given (galaxy-averaged) ΣSFR over much larger physical scales than local (ultra)luminous infrared galaxies. However, on 500 pc scales, they do not exceed the Eddington limit set by radiation pressure on dust. If confirmed by kinematics, the potential presence of nonaxisymmetric structures would provide a means for net angular momentum loss and efficient star formation, helping to explain the very high star formation rates measured in SMGs.

Item Type:Article
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Publisher statement:© 2019. The American Astronomical Society. All rights reserved.
Date accepted:09 April 2019
Date deposited:30 May 2019
Date of first online publication:13 May 2019
Date first made open access:30 May 2019

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