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B How far back can we see

  1. Mar 3, 2016 #1

    wolram

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    Here is a galaxy at very high Z, i thought that Z=7 was a limit before re ionization, so how much further back will we see with better optics ?
    http://arxiv.org/pdf/1603.00461.pdf
     
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  3. Mar 3, 2016 #2

    Simon Bridge

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    Right back to the initial creation of photons.
     
  4. Mar 3, 2016 #3

    wolram

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    Hi Simon, perhaps i should have asked the question in a different way, How far back will we be able to see galaxies Z-11.1 seems a long way to me.
     
  5. Mar 3, 2016 #4

    Simon Bridge

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    Maybe back to the formation of the first galaxies and proto-galaxies ... I think the visible horizon is farther away than that in this epoch.
    However, you should understand that these redshifts are estimates - there is not enough data to pin them down.
     
  6. Mar 3, 2016 #5

    wolram

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    Thank you for the clarification SB.
     
  7. Mar 3, 2016 #6

    russ_watters

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  8. Mar 3, 2016 #7

    Chronos

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  9. Mar 3, 2016 #8

    mfb

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    And it is not expected to see earlier galaxies simply because there were no galaxies (to our current knowledge).

    Some individual stars formed earlier according to the linked page, but detecting those would need a telescope orders of magnitude better.
     
  10. Mar 3, 2016 #9

    Chronos

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    Yes, the first stars are believed to predate the first galaxies by a considerable margin - probably around z~20 - ,but, Individual stars are deemed to be to be optically undetectable at such vast distances. They are already difficult enough to resolve with existing telescopes in even our nearest neighboring galaxies.
     
  11. Mar 3, 2016 #10

    mfb

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    A back of the envelope calculation:
    Typical properties (page 7) -> the higher temperatur cancels a redshift factor of ~18, so their spectrum is not that far away from a solar spectrum. The sun has an absolute magnitude of ~5, 1 million times this luminosity (worst case) would give them an apparent magnitude of -10.
    Cosmology calc -> z=20 gives a luminous distance of 230 GPc, or a difference of apparent and absolute magnitude of 57. Combining both, we get an apparent brightness of 47mag. With the upper value for their luminosity, this improves to 40mag.
    The limiting magnitude for E-ELT (under construction) is around 36mag, still out of reach even with perfect conditions. Well, at least we don't need planet-sized telescopes...
     
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