ALMA 200 pc resolution imaging of smooth cold dusty disks in typical z ∼ 3 star-forming galaxies

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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 Mꙩ 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.
© 2019. The American Astronomical Society. All rights reserved. Artículo firmado por 17 autores. The authors would like to thank Jacqueline Hodge, Erica Keller, Victor de Souza Magalhaes, Jérome Pety, Gergö Popping, Alvio Renzini, David Ruffolo, Kamolnate Trisupatsilp, and Fabian Walter for helpful discussions and suggestions. W.R. acknowledges support from the Thailand Research Fund/Office of the Higher Education Commission grant No. MRG6280259; Chulalongkorn University’s CUniverse and the Ratchadapiseksompot Endowment Fund. P.G.P-G. acknowledges support from the Spanish Government grant AYA2015-63650-P. G.E.M. acknowledges support from the Villum Fonden research grant 13160 “Gas to stars, stars to dust: tracing star formation across cosmic time,” the Cosmic Dawn Center of Excellence funded by the Danish National Research Foundation, and the ERC Consolidator Grant funding scheme (project ConTExt, grant number No. 648179). K.K. and T.W. acknowledge the support from JSPS KAKENHI grant No. JP17H06130 and the NAOJ ALMA Scientific Research grant No. 2017-06B. C.C.W. acknowledges support from the NSF Astronomy and Astrophysics Fellowship grant AST-1701546. Kavli IPMU is supported by World Premier International Research Center Initiative (WPI), MEXT, Japan. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2017.1.00001.S, #2016.1.00048.S, #2015.1.00948.S, #2012.1.00173.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), and NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.
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