ALMA 200 pc Resolution Imaging of Smooth Cold Dusty Disks in Typical z ∼ 3 Star-forming Galaxies

W. Rujopakarn, E. Daddi, G. H. Rieke, A. Puglisi, M. Schramm, P. G. Pérez-González, G. E. Magdis, S. Alberts, F. Bournaud, D. Elbaz, M. Franco, L. Kawinwanichakij, K. Kohno, D. Narayanan, J. D. Silverman, T. Wang, C. C. Williams

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21 Citations (Scopus)


We present high-fidelity, 30 mas (200 pc) resolution ALMA rest-frame 240 μm observations of cold dust emission in three typical main-sequence star-forming galaxies (SFGs) at z ∼ 3 in the Hubble Ultra-Deep Field (HUDF). The cold dust is distributed within the smooth disklike central regions of star formation 1-3 kpc in diameter, despite their complex and disturbed rest-frame UV and optical morphologies. No dust substructures or clumps are seen down to ≃1-3 yr-1 (1σ) per 200 pc beam. No dust emission is observed at the locations of UV-emitting clumps, which lie ≃2-10 kpc from the bulk of star formation. Clumpy substructures can contribute no more than 1%-7% of the total star formation in these galaxies (3σ upper limits). The lack of star-forming substructures in our HUDF galaxies is to be contrasted with the multiple substructures characteristic of submillimeter-selected galaxies (SMGs) at the same cosmic epoch, particularly the far-IR-bright SMGs with similarly high-fidelity ALMA observations of Hodge et al. Individual star-forming substructures in these SMGs contain ∼10%-30% of their total star formation. A substructure in these SMGs is often comparably bright in the far-infrared to (or in some cases brighter than) our typical SFGs, suggesting that these SMGs originate from a class of disruptive events involving multiple objects at the scale of our HUDF galaxies. The scale of the disruptive event found in our main-sequence SFGs, characterized by the lack of star-forming substructures at our resolution and sensitivity, could be less violent, e.g., gas-rich disk instability or minor mergers.
Original languageEnglish
Article number107
Number of pages20
JournalThe Astrophysical Journal
Issue number2
Early online date9 Sept 2019
Publication statusPublished - 10 Sept 2019


  • Evolution-galaxies
  • Formation-galaxies
  • Galaxies
  • High-redshift-galaxies
  • Star formation-galaxies
  • Structure


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