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The first galaxies

  1. Mar 26, 2009 #1
    How old was the universe after the big bang when galaxies started forming?
     
  2. jcsd
  3. Mar 26, 2009 #2

    mgb_phys

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  4. Mar 27, 2009 #3

    Chalnoth

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    Well, we've seen galaxies out to about z=7, but yes, somewhere around 750 million years.
     
  5. Mar 28, 2009 #4

    Chronos

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    It is safe to say none originated before 400 million years after the big bang. No reason to rule out any afterwards.
     
  6. Mar 30, 2009 #5
    Is there any problem with the observation of mature, well-formed galaxies at higher redshift than previously expected?
     
  7. Mar 30, 2009 #6

    Chalnoth

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    I'm not so sure that this is the case. The exact formation of the early galaxies has always been uncertain, just because the observations haven't been there.
     
  8. Mar 30, 2009 #7
  9. Mar 30, 2009 #8

    Chalnoth

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    You should take all science-related news items with a huge grain of salt. They're often wildly distorted, sometimes just flat wrong.

    So far as I know, everybody basically expects a hierarchical formation of galaxies, where galaxies in the densest regions formed first, and galaxies in less dense regions formed later. I don't think there's been anything yet produced that challenges this view, though there are many details that remain to be understood.
     
  10. Mar 30, 2009 #9
    Well, these are not news, but a scientific article appeared in Nature:
    Cimatti, A. et al., Nature 430 (2004) 184-187.
     
  11. Mar 30, 2009 #10

    Chalnoth

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    Okay.
    http://www.nature.com/nature/journal/v430/n6996/full/nature02668.html

    Key point:
    A good rule of thumb when it comes to stuff like this is that simulations not backed by observation are often wrong.
     
    Last edited by a moderator: May 4, 2017
  12. Mar 30, 2009 #11
    The nature paper is an observational report, contrarily to what you seem to suggest...
     
  13. Mar 30, 2009 #12

    Chalnoth

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    That wasn't my point. My point was that I rather doubt that most physicists were actually surprised by the news that the simulations were entirely accurate.
     
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