The most ancient spiral galaxy confirmed

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Nov 4, 2017.

  1. paddoboy Valued Senior Member

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    The most ancient spiral galaxy confirmed
    November 3, 2017

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    Spiral galaxy A1689B11 sits behind a massive cluster of galaxies that acts as a lens, producing two magnified images of the spiral galaxy in different positions in the sky. Credit: James Josephides
    The most ancient spiral galaxy discovered to date is revealing its secrets to a team of astronomers at Swinburne University of Technology and The Australian National University (ANU), part of the Australian Research Council Centre of Excellence in All Sky Astrophysics in 3-D (ASTRO 3-D).

    The galaxy, known as A1689B11, existed 11 billion years in the past, just 2.6 billion years after the Big Bang, when the universe was only one fifth of its present age. It is thus the most ancient spiral galaxy discovered so far.

    The researchers used a powerful technique that combines gravitational lensing with the cutting-edge instrument the Near-infrared Integral Field Spectrograph (NIFS) on the Gemini North telescope in Hawai'i to verify the vintage and spiral nature of this galaxy. NIFS is Australia's first Gemini instrument that was designed and built by the late Peter McGregor at The ANU.



    Read more at: https://phys.org/news/2017-11-ancient-spiral-galaxy.html#jCp
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    the paper:

    THE MOST ANCIENT SPIRAL GALAXY: A 2.6-GYR-OLD DISK WITH A TRANQUIL VELOCITY FIELD

    ABSTRACT
    We report an integral-field spectroscopic (IFS) observation of a gravitationally lensed spiral galaxy A1689B11 at redshift z = 2.54. It is the most ancient spiral galaxy discovered to date and the second kinematically confirmed spiral at z & 2. Thanks to gravitational lensing, this is also by far the deepest IFS observation with the highest spatial resolution (∼ 400 pc) on a spiral galaxy at a cosmic time when the Hubble sequence is about to emerge. After correcting for a lensing magnification of 7.2 ± 0.8, this primitive spiral disk has an intrinsic star formation rate of 22 ± 2 M⊙ yr−1 , a stellar mass of 109.8±0.3M⊙ and a half-light radius of r1/2 = 2.6 ± 0.7 kpc, typical of a main-sequence star-forming (SF) galaxy at z ∼ 2. However, the Hα kinematics show a surprisingly tranquil velocity field with an ordered rotation (Vc = 200 ± 12 km s−1 ) and uniformly small velocity dispersions (Vσ,mean = 23 ± 4 km s−1and Vσ,outer−disk = 15 ± 2 km s−1 ). The low gas velocity dispersion is similar to local spiral galaxies and is consistent with the classic density wave theory where spiral arms form in dynamically cold and thin disks. We speculate that A1689B11 belongs to a population of rare spiral galaxies at z & 2 that mark the formation epoch of thin disks. Future observations with JWST will greatly increase the sample of these rare galaxies and unveil the earliest onset of spiral arms.
     
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  3. paddoboy Valued Senior Member

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    I just put a hypothetical thought of mine to our experts over at another forum....
    Galaxies are thought to have formed within the first 3 to 4 hundred million years post BB...They underwent many mergers, collisions etc as the universe was a lot more violent then and more elliptical and irregular galaxies, before settling down and letting density waves form the spiral structure that we see in many galaxies today.
    Perhaps this spiral galaxy in question and the occasional other, were first formed in more or less isolation and did not undergo mergers and collisions that would have upset the density waves actions and consequently spiral arms. Those density waves and resultant spiral arms would then have had more time to work their magic and formed earlier. That possibility was recognised.
     
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  5. paddoboy Valued Senior Member

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    http://nineplanets.org/news/oldest-spiral-galaxy-yet-found/

    excerpt:
    “This galaxy is forming stars 20 times faster than galaxies today – as fast as other young galaxies of similar masses in the early Universe. However, unlike other galaxies of the same epoch, A1689B11 has a very cool and thin disc, rotating calmly with surprisingly little turbulence. This type of spiral galaxy has never been seen before at this early epoch of the Universe!”

     
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