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Big bang?

  1. Jan 18, 2006 #1
    After the discovery of galaxy HUDF-JD2 is the big bang theory to be revised?
     
  2. jcsd
  3. Jan 18, 2006 #2

    Garth

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    Hi roland, and welcome to these Forums!
    You didn't have to submit your thread twice! I expect you know that and only hit the 'submit' button twice by mistake.
    This has been discussed before here: Is there an Age Problem in the Mainstream Model?. In that thread I said (refering to HUDF-JD2):
    Does that answer your question?

    Garth
     
    Last edited: Jan 19, 2006
  4. Jan 18, 2006 #3

    Nereid

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    There's also the question "how certain are we of the distance and nature of this spot of fuzz?"

    For starters, despite many hours with a VLT, a Keck, and a Gemini, no spectrum was detected (so the distance estimate remains a photometric one, and galaxy SED modeling not at all well constrained).

    For seconds, if it is so young, who's to say that galaxy evolution models are particularly accurate? (I realise you can reverse the logic, but you still have just one data point).

    And last (for now), is anyone brave enough to be confident about the selection effects?

    Rumours of the danger posed by HUDF-JD2 to consensus cosmology models are greatly exaggerated.
     
  5. Jan 19, 2006 #4
    Rumours of the danger posed by HUDF-JD2 may be the tip of the iceberg. We must await the launch and deployment of JWST. However I shall never cease to be ammused. Merci Garth.
     
  6. Jan 19, 2006 #5

    Garth

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    But we also have high-z quasars with significant iron abundances, and iron is the last element to be formed in fusion processes. In particular there is: APM 08279+5255at z = 3.91 whose age is 2.1 Gyr when the universe was only 1.6 Gyrs old (according to LCDM model expansion).

    This age estimate is consistent with Cosmological implications of APM 08279+5255, an old quasar at z= 3.91 Alcaniz J.S.; Lima J.A.S.; Cunha J.V, Monthly Notices of the Royal Astronomical Society, Volume 340, Number 4, April 2003, pp. L39-L42(1)

    But these age estimates are not consistent with the LCDM age of the universe at z = 3.91.

    This point is emphasised by Drs. Norbert Schartel, Fred Jansen and Prof. Guenther Hasinger in their ESA web-page article Is the universe older than expected?

    There are other examples of early iron high abundances: at z = 3.104,
    The First XMM-Newton spectrum of a high redshift quasar - PKS 0537 ,
    (Oct 2000).

    And six quasars at z>4
    Restless quasar activity: from BeppoSAX to Chandra and XMM-Newton
    (2004)

    Garth
     
    Last edited: Jan 19, 2006
  7. Jan 19, 2006 #6

    Nereid

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    Two things (for Garth and roland):

    I was responding to the OP (Rumours of the danger posed by HUDF-JD2 to consensus cosmology models) - your reply Garth (a good one) says nothing of HUDF-JD2, and the caveats I made about interpreting the meagre data we have on it.

    Quasars are not galaxies; despite decades of intense scrutiny, much remains to be learned about quasars, esp what's really going on in the central engine, and just what the accretion disk (and jet) can, and cannot, produce in the way of nucleosynthesis.

    And since we're on the subject, another (more recent) mystery is the formation of the SMBH which lie at the heart of quasars (and the nuclei of - most? all?? - galaxies) - which begat what? Was there only one formation mechanism? Are the all alike anyway??

    To be sure, it's a very exciting time to doing astronomy; and an even more exciting time to be doing observational cosmology, a field that's what, less than 50 years old (if you don't count Olbers and the Hubble relationship)? At the same time, it's also frustrating; I doubt that any of us will live to see some of today's central questions in cosmology resolved, let alone the answer to David Hilbert's sixth problem ("Can physics be axiomatized?" - this is one of only what, three (of 23) that remain, today, unsolved).
     
  8. Jan 19, 2006 #7

    Garth

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    Hi Nereid.
    I was expanding on roland's point above and I think the age problems are related. I discussed HUDF-JD2 in the former thread linked to above.

    The point is that there are now several observations, I have referred to nine, in which old features, particularly high iron content, are observed at (mostly unambiguous) high red shift.

    It takes time to synthesise iron and, as I quoted myself saying in post #2 above, we may have to revise our nucleosynthesis models, however, these observations may also be indications that the universe is older than we expect.
    That observational fact (old features in an early universe) has to be flagged up when critically accepting the standard theoretical cosmological model.

    Garth
     
    Last edited: Jan 19, 2006
  9. Jan 8, 2010 #8

    sylas

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    I realize this is a very old thread, but after fielding questions about HUDF-JD2 in another context, this thread showed up in a google search so it may be worth putting this on record, as others may find it the same way I did.

    It seems likely that the original identification of HUDF-JD2 was mistaken. In 2005 it was reported as a galaxy at redshift z~6.5, with a mass of about 6*1011 solar masses. Reference:
    Even then, the report noted an alternative interpretation of a galaxy at about z~2.5 could not be ruled out.

    Subsequent work has suggested that the original distance estimate was incorrect, and a lower redshift value is to be preferred.
    This proposes that it is at z~1.7.

    There is other more recent work on high redshift galaxies which make stronger candidates than HUDF-JD2.

    Cheers -- sylas
     
  10. Jan 8, 2010 #9

    Garth

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    Yes, it seems the HUDF-JD2 mystery is being resolved, however there are other high iron content objects in the early universe such as An old quasar in a young dark energy-dominated universe?.

    But they too could be resolved with further data or knowledge of metallicity production in the early universe.

    Cheers,

    Garth
     
  11. Jan 8, 2010 #10

    Chronos

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    The population I issue remains unresolved. Iron may have evolved more rapidly than suspected in huge, metal deficient primordial stars.
     
  12. Jan 9, 2010 #11

    Garth

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    Hi Chronos.

    I think you mean the Pop III issue!

    There certainly is a lot of metallicity at z ~ 4 - 5 as in my post #5 above, but Pop III stars are expected to have very short lifetimes so they should explain it.



    Regards,
    Garth
     
    Last edited: Jan 9, 2010
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