* Astronomy

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Q2343-BX442

Blobrana · L

Title: High Velocity Dispersion in A Rare Grand Design Spiral Galaxy at Redshift z=2.18
Authors: David R. Law, Alice E. Shapley, Charles C. Steidel, Naveen A. Reddy, Charlotte R. Christensen, Dawn K. Erb

Although relatively common in the local Universe, only one grand-design spiral galaxy has been spectroscopically confirmed to lie at z>2 (HDFX 28; z=2.011), and 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 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 redshifts <2, the velocity dispersion of disks decreases, and spiral galaxies are more numerous by z~1. Here we report observations of the grand design spiral galaxy Q2343-BX442 at z=2.18. Spectroscopy of ionised 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 their rarity.

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Astronomers report the earliest spiral galaxy ever seen, a shocking discovery

Astronomers have witnessed for the first time a spiral galaxy in the early universe, billions of years before many other spiral galaxies formed. In findings reported July 19 in the journal Nature, the astronomers said they discovered it while using the Hubble Space Telescope to take pictures of about 300 very distant galaxies in the early universe and to study their properties. This distant spiral galaxy is being observed as it existed roughly three billion years after the Big Bang, and light from this part of the universe has been travelling to Earth for about 10.7 billion years.
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