A massive, dead disk galaxy in the early Universe
Sune Toft, Johannes Zabl, Johan Richard, Anna Gallazzi, Stefano, Zibetti, Moire Prescott, Claudio Grillo, Allison W.S. Man, Nicholas Y. Lee,, Carlos Gomez-Guijarro, Mikkel Stockmann, Georgios Magdis, Charles L., Steinhardt

TL;DR
This study reveals that a massive, compact galaxy at redshift 2 is actually a fast-spinning disk galaxy, challenging the idea that such galaxies formed solely through mergers and nuclear starbursts.
Contribution
It provides direct high-resolution evidence that some early massive galaxies formed as rotationally supported disks, not just through mergers, altering our understanding of galaxy evolution.
Findings
The galaxy is a rotationally supported disk, not a merger remnant.
Stars formed in a disk, not in a nuclear starburst.
Cold gas streams fed the galaxy until shock heating halted accretion.
Abstract
At redshift z = 2, when the Universe was just three billion years old, half of the most massive galaxies were extremely compact and had already exhausted their fuel for star formation(1-4). It is believed that they were formed in intense nuclear starbursts and that they ultimately grew into the most massive local elliptical galaxies seen today, through mergers with minor companions(5,6), but validating this picture requires higher-resolution observations of their centres than is currently possible. Magnification from gravitational lensing offers an opportunity to resolve the inner regions of galaxies(7). Here we report an analysis of the stellar populations and kinematics of a lensed z = 2.1478 compact galaxy, which surprisingly turns out to be a fast-spinning, rotationally supported disk galaxy. Its stars must have formed in a disk, rather than in a merger-driven nuclear starburst(8).…
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