Although grand-design spiral galaxies are relatively common in the local Universe, only one has been spectroscopically confirmed to lie at redshift z > 2 (HDFX 28; z = 2.011); and it may prove to be a major merger that simply resembles a spiral in projection. The rarity of spirals has been explained as a result of disks being dynamically 'hot' at z > 2 (refs 2-5), which may instead favour the formation of commonly observed clumpy structures. Alternatively, current instrumentation may simply not be sensitive enough to detect spiral structures comparable to those in the modern Universe. At z < 2, the velocity dispersion of disks decreases, and spiral galaxies are more numerous by z ≈ 1 (refs 7, 13-15). Here we report observations of the grand-design spiral galaxy Q2343-BX442 at z = 2.18. Spectroscopy of ionized gas shows that the disk is dynamically hot, implying an uncertain origin for the spiral structure. The kinematics of the galaxy are consistent with a thick disk undergoing a minor merger, which can drive the formation of short-lived spiral structure. A duty cycle of <100 Myr for such tidally induced spiral structure in a hot massive disk is consistent with its rarity.
A Galaxy at a Redshift Z = 6.96M Iye et al. Nature 443 (7108), 186-8. PMID 16971942.When galaxy formation started in the history of the Universe remains unclear. Studies of the cosmic microwave background indicate that the Universe, after initial cooling …
A Massive, Dead Disk Galaxy in the Early UniverseS Toft et al. Nature 546 (7659), 510-513. PMID 28640271.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 s …
Strongly Baryon-Dominated Disk Galaxies at the Peak of Galaxy Formation Ten Billion Years AgoR Genzel et al. Nature 543 (7645), 397-401. PMID 28300118.In the cold dark matter cosmology, the baryonic components of galaxies-stars and gas-are thought to be mixed with and embedded in non-baryonic and non-relativistic dark m …
High Star Formation Rates as the Origin of Turbulence in Early and Modern Disk GalaxiesAW Green et al. Nature 467 (7316), 684-6. PMID 20930839.Observations of star formation and kinematics in early galaxies at high spatial and spectral resolution have shown that two-thirds are massive rotating disk galaxies, wit …
A Massive, Quiescent, Population II Galaxy at a Redshift of 2.1M Kriek et al. Nature 540 (7632), 248-251. PMID 27929014.Unlike spiral galaxies such as the Milky Way, the majority of the stars in massive elliptical galaxies were formed in a short period early in the history of the Universe. …