A massive, dead disk galaxy in the early Universe
  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). The
galaxy was probably fed by streams of cold gas, which were able to penetrate
the hot halo gas until they were cut off by shock heating from the dark matter
halo(9). This result confirms previous indirect indications(10-13) that the
first galaxies to cease star formation must have gone through major changes not
just in their structure, but also in their kinematics, to evolve into
present-day elliptical galaxies.
