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A dynamically cold disk galaxy in the early Universe



In a recent paper, Rizzo and collaborators present an image reconstruction of a dynamically cold, highly star-forming, rotating disk in galaxy SPT–S J041839–4751.9, at redshift z = 4.2, which is strongly gravitationally lensed by a foreground galaxy at z = 0.263.

The top panel shows the emission of the 158-μm fine-structure line of ionized carbon [C II] integrated across a velocity range of 721 km s−1 (zeroth-moment map), as observed with ALMA. The beam size, shown as a white ellipse on the lower left corner, is 0.19″ × 0.17″ at a position angle of −85.22°. 

The reconstructed image of the z=4.2 galaxy is shown in the bottom panel: it is a typical dusty starburst, with global star-forming and dust properties that are in agreement with current numerical simulations and observations. The authors also derived a rotation curve with the typical shape of nearby massive spiral galaxies, which demonstrates that at least some young galaxies are dynamically akin to those observed in the local Universe, and only weakly affected by extreme physical processes.