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Massive objects with super-solar metallicities at z~6

  1. z~6 Current observations leave no time for them to have formed.

    22.2%
  2. z~8

    0 vote(s)
    0.0%
  3. z~10

    0 vote(s)
    0.0%
  4. z~12

    0 vote(s)
    0.0%
  5. z~14

    0 vote(s)
    0.0%
  6. z~16

    0 vote(s)
    0.0%
  7. z~18

    0 vote(s)
    0.0%
  8. z~20

    44.4%
  9. No such observations can falsify the BB

    22.2%
  10. Other

    22.2%
Multiple votes are allowed.
  1. Oct 29, 2005 #1

    turbo

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    Fan et al published a paper several years ago that has since garnered over 200 citations, many of them recent. The authors studied the spectra of three objects at z~6 and determined that the objects are quasars, each with masses of several billions of Suns, residing in massive hosts, each with a lower mass limit of 10 trillion Suns. To top it off, the spectra of these objects indicate that they have super-solar metallicities.

    http://www.journals.uchicago.edu/AJ/journal/issues/v122n6/201316/201316.text.html

    I have a question for the denizens of General Astronomy and Cosmology: Does the observation of extremely massive objects with super-solar metallicity at z~6 pose enough problems with the heirarchical model of structure formation to falsify the Big Bang theory? If not, at what epoch would such observations falsify the BB?
     
  2. jcsd
  3. Oct 29, 2005 #2
    I think this is a good question. I am not sure of the exact answer to this, but I think the z~6 observations can be explained away as extreme objects, analogous to ULIRGS etc at lower redshifts. I think the new generatons telescopes will unvail less extreme objects at the same redshift, but I don't think there will be much to see at higher redshifts. Obvously if we see things at z~20 like these extreme objects, there will be some trouble!
     
  4. Oct 29, 2005 #3

    turbo

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    Isn't z~20 about the time of first light - the period when the low-metallicity Pop III stars begin to ignite? These are the stars that supposedly supplied the metals from which these structures must have formed. We've got to allow some time for these stars to form and to go supernova to provide the metallicity of the IGM. What's your best guess for the time scale?
     
  5. Oct 29, 2005 #4
    I don't know, turbo-1. I think this would probably take some pretty detailed calculations to work out. Simulations need to be done including both baryons and dark matter, plus we need to know the IMF etc, which is a challenge to determine even locally. z~20 is just an overestimate on my part because I don't know at exactly which redshift massive, metal rich objects will rule out standard big bang.
     
  6. Oct 30, 2005 #5

    Chronos

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    Early metallicity is really not a player these days. Reionization studies already push the envelope way past z~6. That is a bigger issue in my mind. There is also the problem of observing objects past z~10. There is a huge amount of neutral hydrogen that absorbs the wavelengths of interest.
     
  7. Oct 30, 2005 #6

    Garth

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    This has already been discussed in Is there an Age Problem in the Mainstream Model? .

    There is already a problem with quasar APM 08279+5255 at a red shift of 3.91, which in the concordance model yields a universe age of 1.6 Gyr., a little short of the 3 - 2 Gyr required to produce its metallicity of 2 - 3 times solar. One paper to check is An old quasar in a young dark energy-dominated universe?.

    Already we have to reconcile the present observations by either modifying our stellar nucleosynthesis model or the cosmological model.

    As I have no idea how the stellar nucleosynthesis model could be modified I could not vote in this poll.

    Garth
     
  8. Oct 30, 2005 #7

    Chronos

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    Oh come on, Garth. There are many possible explanations. Let's not cherry pick them. You are a bright guy, what alternative explanations might fit?
     
  9. Oct 30, 2005 #8

    Garth

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    The data is mis-interpreted,or contaminated?
     
  10. Oct 30, 2005 #9

    turbo

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    This has been discussed, yes, but I want to know how people on this forum address the issue, and quantify it. I hope that as people vote, they will also explain the reasoning behind their opinions. There are some very bright people hanging out here and I want to know if they think that the BB theory can be falsified by observations and not merely further constrained. It's an important question, with implications that extend to the very nature and value of scientific inquiry.
     
  11. Oct 30, 2005 #10

    SpaceTiger

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    I've said it many times before and I will say it again. You can't, at this moment, falsify or confirm the big bang based on metallicity measurements. Metal enrichment is one of the most difficult processes to model in astrophysics today and metallicity measurements are unreliable, particularly at high-redshift. This is not like big bang nucleosynthesis, where the theory has a very specific set of predictions that can be derived from the basic parameters of the universe. You need to understand Pop III stellar nucleosynthesis, Pop III supernovae, the growth of structure at high-redshift, the growth and distribution of quasars, the low-metallicity stellar IMF, and probably more. We don't have what I would call a satisfactory understanding of any of those things.

    I voted "Other" because I don't know, or even have an inkling of, the answer. I don't think anybody does. It could be that, when all the calculations and observations are done, the big bang would be falsified with supersolar metallicities at z~3. However, I very seriously doubt it and, if forced, I would probably tend towards high redshifts (~20). But that would be little more than a guess at this point.
     
  12. Oct 30, 2005 #11

    turbo

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    Thanks, ST. The hosts for these quasars are massive, though, and that is a factor. With lower limits on their masses of 10 trillion MSol, these are very large structures to observe so early in the life of the universe.
     
  13. Oct 31, 2005 #12

    Chronos

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    I do agree with ST's position. Nucleosynthesis is a wild guess in the observable universe. I voted for z~20 because the BB models seems to exclude most other possibilities and there are studies suggesting this is a reasonable threshold to test the model. Unfortunately, there are other studies that suggest this realm is difficult, if not impossible, to probe. I hope there are ways around this.
     
  14. Oct 31, 2005 #13

    hellfire

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    I voted z ~ 20 thinking mainly about the current cosmological model, may be with some possible variations, but now I am not really sure whether z ~ 20 would actually disprove every cosmological model based on big-bang. May be I had better voted "No such observations can falsify the BB" or "Others"...
     
    Last edited: Oct 31, 2005
  15. Oct 31, 2005 #14

    Chronos

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    I think z~20 is a very reasonable limit without breaking the bank. Any finite model in time must break down before the physics do.
     
  16. Nov 3, 2005 #15
    I voted for z=20, tho I would not be seriously uncomfortable until z=40. In those intervals, the speed of aging/evolution in the young universe can be fine-tuned by the addition of Primordial Black Holes (of mass greater than Luna), and stable decay relics of those with mass less than Luna. Those latter would be essentially massive WIMPs of neutral charge (possibly SUSY particles, possibly 'other'). In the mass range between a mountain and Luna, we would 'detect' them as low-mass BH's which for some reason don't decay via Hawking radiation, tho they might radiate due to infalling matter causing transient instability.

    The number of epicycles is limited only by imagination. Falsifying the BB becomes a ... doctrinal issue. S
     
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