Quasars and Cosmology

  1. turbo

    turbo 7,366
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    SDSS is perhaps the most ambitious astronomical survey ever undertaken, and it has provided a wealth of new data. Unfortunately for cosmologists (or fortunately, if cosmologists are willing to re-group), some of the findings are quite inconsistent with their expectations.

    Scroll down to Nov 2, 2005 and watch Michael Strauss' presentation to the Space Telescope Science Institute. Strauss is the scientific spokesperson for the Sloan Digital Sky Survey, and has co-authored many ground-breaking papers. There are several points that he makes about quasars in this presentation that should give any loyal BB-adherent pause.

    1) SDSS has observed quasars out to z~6.5. Because luminosity falls off as a function of the square of the distance (absent absorption), if quasars are at the distances implied by their redshifts, these distant quasars would have be be powered by black holes of several billion Solar masses, cannibalizing host galaxies of over a trillion Solar masses. Since z~6.5 corresponds to a time a few hundred million years after the BB, how did these monsters have time to form?

    2) These high-z quasars have solar or super-solar metallicities. Our Sun is presumably the product of generations of supernovae, so how did these massive bodies get so metal-enriched so early?

    3) Because elements are formed in stars through different processes, cosmologists expected to see some evolution in the metallicities of quasars with redshift. SDSS found none, even out to z~6.5, either in absolute or relative metallicity.

    4) Cosmologists expected that higher-redshift quasars would stand a much higher chance of being lensed because of the very long distances and the increased chance of intervening massive objects on our line-of-sight to them. None of the z=5.7-6.5 quasars in the SDSS survey are lensed.

    Strauss points out in this presentation that theorists have not been able to reconcile these observations with the current cosmological model. He is not a maverick - he is a senior member of perhaps the most prestigious observational consortium operating today, and his words bear heeding.

    Astronomy is a purely observational science. Cosmology is an exercise in model-building based on these observations. When observations conflict with theoretical models, the models must be changed. It has been over 3 years since Strauss, Fan, et al starting publishing and speaking about their observations, and still I see no evidence that cosmologists have changed their models to accommodate these observations. Good science requires us to change models when the models conflict with well-controlled, repeatable observations.


    Edit: New URL.
    http://www.stsci.edu/institute/itsd/information/streaming/archive/STScIScienceColloquiaFall2005/
     
    Last edited: Dec 30, 2008
  2. jcsd
  3. Nereid

    Nereid 4,014
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    "Resource Not Found!"

    Do you have a different source, a different URL perhaps?
     
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  4. turbo

    turbo 7,366
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    Last edited by a moderator: Dec 30, 2008
  5. Nereid

    Nereid 4,014
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    (bold added)
    Do you mean "Fan, Xiaohui"?

    Who are the "et al."?

    Which of the many papers by "Strauss, Fan, et al", published in the last three years, do you consider the most important, in terms of publishing observations which "conflict with theoretical models" (in the LCDM paradigm)? I ask for several reasons; one such reason is that I went looking for these papers, and found none (in the quick search I've done so far) that fit your summary (in the post of yours I'm quoting) ...

    ... for example: "4) Cosmologists expected that higher-redshift quasars would stand a much higher chance of being lensed because of the very long distances and the increased chance of intervening massive objects on our line-of-sight to them. None of the z=5.7-6.5 quasars in the SDSS survey are lensed." Here is one Strauss, Fan, et al. paper, published in 2006, of apparent relevance to this claim: A Snapshot Survey for Gravitational Lenses among z>=4.0 Quasars. II. Constraints on the 4.0<z<5.4 Quasar Population. Here's the abstract (some formatting lost, bold added):
    IOW, normal science at work; no cherry picking, no suppression, ...

    ... and no "findings [] quite inconsistent with [cosmologists'] expectations"!
     
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  6. turbo

    turbo 7,366
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    I did not mention more than Fan and Strauss because typically SDSS papers list many, many authors and they are often near the head of the author list. Nor did I suggest that the SDSS observations are an example of cherry picking on their part. The refusal by theorists to address the observations mentioned by Strauss in his presentation IS an example of cherry-picking. When observations point out inconvenient truths, they should be addressed, not ignored.

    You made a long follow-up post just a few minutes after I posted the new link. Strauss' presentation is quite detailed and it will take a lot of time to watch. Please watch/listen to the Strauss presentation before you make claims about the problems I noted. There are quite a number of observations that conflict with modern cosmology's notion of the nature of quasars.
     
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  7. Nereid

    Nereid 4,014
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    There are quite a number of observations that conflict with modern cosmology's notion of the nature of quasars. - turbo-1

    Thanks for the new URL, I'll certainly check it out.

    In the meantime, may I ask you to provide some specific details of how and where quasars* are covered in Disney's paper? in Lieu's?

    * "modern cosmology's notion of the nature of quasars"
     
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  8. Nereid

    Nereid 4,014
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    OK, I've listened to the presentation, downloaded the ~100MB powerpoint supporting material, and read it.

    I can see some similarities to what's in Strauss' presentation, and the PPT slides, and your four points, but I did not notice that he said any of those four points, in the form you present them (I appreciate that you are summarising).

    Would you be kind enough to give slide numbers (out of the 100 total) that match each of these points?

    "Strauss points out in this presentation that theorists have not been able to reconcile these observations with the current cosmological model." - turbo-1

    Strauss certainly pointed to many interesting observations, and puzzles! However, I seem to have missed the part where he pointed out "that theorists have not been able to reconcile these observations with the current cosmological model". Would you mind telling readers where he says this?

    "Which of the many papers by "Strauss, Fan, et al", published in the last three years, do you consider the most important, in terms of publishing observations which "conflict with theoretical models" (in the LCDM paradigm)?" - Nereid

    May I ask my question again?
     
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  9. turbo

    turbo 7,366
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    I'll tell you what - let's start out with the properties of z~6.5 quasars and see if you can find a way to explain them with modern concordance cosmology.

    First, using the Eddington accretion limit to estimate the masses of the quasars' black holes, they are ultra-massive, averaging several billions of Solar masses. This stands the hierarchical model of formation on its head. Massive bodies supposedly accreted gravitationally from smaller bodies. This puts cosmology in a bind because these ultra-massive bodies needed time to form, yet we see them at just 800M years after the BB.

    Next, according to our theories of stellar evolution, the earliest stars were metal-poor. Metals were created, distributed, and re-concentrated by generations of supernovae. Yet, here we see quasars at z~6.5 that have as much or MORE metallicity than our Sun, only 800M years after the BB.

    As Strauss pointed out, MgII and FeII are formed by different types of supernovae, so cosmologists expected to see an evolution in the relative concentration of these metals with redshift. None is seen. There is no detectable difference in high-redshift and low-redshift quasars in any of the metrics they applied.

    None of these puzzles have been explained in light of modern cosmology, unless some recent papers flew under my radar.
     
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  10. Nereid

    Nereid 4,014
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    (bold added)
    Perhaps we could start by trying to get a clear definition of a key term (or terms), and then agree on its scope?

    I've bolded several references in your post, turbo-1; would you mind taking the trouble to spell out, in some detail, just what you mean?

    Specifically, I'm trying to understand how tightly the (fine) details of quasar evolution are related to LCDM cosmological models, as you understand it.
     
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  11. Nereid

    Nereid 4,014
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    I'm still interested to get answers to these questions, turbo-1, not least because I didn't get, from my listening to the presentation and reading of the powerpoint slides, the points you made. For sure I've missed some stuff, but I was particularly listening and looking out for the exact points you made, so I'd really appreciate it if you could point me to exactly where Strauss makes the points you make in your posts.
     
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  12. turbo

    turbo 7,366
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    Here is a discussion of the difficulties in fine-tuning hierarchical matter formation to provide ultra-massive quasars at z>6. For the quasars to be as massive as they appear to be, the mass/luminosity conversion would have to be very inefficient so that the mass of the BH can grow as quickly as possible. However, for the quasars to be visible at all at that redshift, the mass/luminosity conversion would have to be very efficient. This argues for a coincidence in which the BH started accreting early, accreted at super-Eddington rates, and then got very luminous at z~6.5.

    http://arxiv.org/abs/astro-ph/0311008

    Star-formation scenarios are similarly constrained with metal enrichment having to happen due to SNIa in dense ellipticals and z~>9, though there is no evidence that the z~6 quasars reside in normally evolving ellipticals. A second possibility is that an "instantaneous" burst of star formation as late as z~7 had enough time to enrich the quasars in that 50 Myr gap. Again, we are confronted with highly speculative scenarios with fortuitous timing that were introduced when observations placed severe constraints on theory. This paper also address what was then perceived (in a very small sample) as some evolution in MgII/FeII metallicity ratio, though more precise SDSS data finds no such evolution. In the BB theory, Pop III stars can be very large and short-lived though some portion of those stars should have been smaller, and still exist today.

    http://arxiv.org/abs/astro-ph/0307264

    There are more papers addressing these observations, and all must posit some pretty out-there mechanisms by which such ultra-massive highly-metallized objects could have already formed by z~6.5. BB cosmologists are working within a time-constraint of ~13Gy and the lack of any type of redshift-related evolution in the qualities of quasars point to a much older universe unless some real miracles are invoked in the first 800M years after the BB. When Webb and the LBT are on-line, I predict that quasars much deeper than z~6.5 will be found and they will continue to show characteristics found by SDSS up to z~6.5.

    Then, there is the puzzle of why quasar Luminosity Function slope spikes after z>3. As Strauss explains in the presentation, there are absolutely no metrics by which quasars evolve with redshift, BUT the LF slope increases sharply after z>3 and theorists have no idea why. He said something about observers giving theorists a hard time because it's their job, or something similar. It's late in the video - around 50 min, IIR.
     
  13. Nereid

    Nereid 4,014
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    This (quasar evolution) is, without a doubt, a fascinating area of research!

    However, I don't understand what it has to do with cosmology (in general), and LCDM models (in particular); can you elaborate please?

    This connection - or lack of it - was one of the reasons why I asked for a clear definition of scope ('cosmology' or 'modern concordance cosmology').
    Indeed, the observations* may point that way ...

    ... or they may point to profound ignorance concerning the details of quasar evolution, ...

    ... or ...

    IOW, a puzzle, the likes of which are found throughout science, and which are an important part of how science progresses.

    I guess one thing I'm curious about is how you (apparently) arrived at the conclusion that lack of understanding of quasar evolution is, without qualification, equivalent to problems with cosmological models; can you elaborate please?
    Which theorists would that be? Names, etc.

    Which theories would this have direct relevance to? Papers, etc.
    Thanks; I'll check it out.

    May I repeat my questions?

    Would you be kind enough to give slide numbers (out of the 100 total), in Strauss' presentation, that match each of your four points?

    Where did Strauss point out "that theorists have not been able to reconcile these observations with the current cosmological model"?

    * of course, the observations themselves do no such thing ... it's only interpretations of the observations, using a mighty array of material from just about all parts of modern physics textbooks, that do so.
     
  14. I do appreciate these sentiments. Well said.

    So ...... just as I thought I was beginning to become convinced that the LCDM model was the fine working hypothesis it is advertised to be ..... here is yet another discrepancy to be accounted for. Together with other puzzles that have been aired in this forum it does make one wonder about the fundamental soundness of the entire elaborate scheme.

    Here's hoping that the chorus of dissent from folk like Richard Lieu and Disney will be properly noticed and answered by mainstream cosmologists in 2009.

    May all contributers to this forum enjoy good health, fortune and wisdom in this new year.
     
  15. turbo

    turbo 7,366
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    A number of years (decades) ago, theorists looked at the redshift-distance relation that Hubble was working on, and decided that the redshift should be regarded as evidence for cosmological expansion. Gamow and others extrapolated this "expansion" back to a beginning and posited a creation event. Thus the BB theory was born. Over the years, tweaking of H0 and other parameters has changed the projected age of the BB universe, until we have gotten to an accepted age of ~13+ Gy. SDSS observations have shown us that if we look back to redshift z~6.5, we find ultra-massive, highly metallized quasars residing there. This has everything to do with cosmology. If we find giant, metal-rich bodies residing at an epoch in which the universe is supposed to be young and metal-poor and dominated by the formation of metal-poor stars (Pop III), then either the universe is much older than the BB model allows, or the hierarchical model of matter formation is wrong and/or the stellar mechanisms by which metals are created (metal-rich stars going SN) are wrong.

    See above answer. We don't have to fully understand quasar evolution to appreciate the problem. The existence of highly-metallized ultra-massive objects at z~6.5 cannot be explained within the context of BB cosmology without invoking some miracles.

    Ask Michael Strauss. He is the one who made the statement in his presentation.

    The points I made are clearly presented in Strauss' talk.
     
  16. Nereid

    Nereid 4,014
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    hi oldman, long time no see.
    So, given that turbo-1 has, so far, not mentioned any of the Strauss, Fan, et al papers presenting observations which conflict with LCDM models, may I ask you if you know of any?

    Here's one source of my irritation (which has, sadly, been evident in my posts): it is all too easy to make claims like this (anyone can put fingers to keyboard). Surely if one does make a claim like this, relevant back-up material should also be provided (if anyone asks for it)?

    After all, if the claims can't be backed up, how seriously should you, oldman, take them?

    And what discrepancy is that, oldman?

    Again, it's very easy to make a claim that may be nothing more than a misunderstanding of the relevant theories - General Relativity is flawed because it can't account for the movement of the LIBOR rates in October 2008, to take a totally ridiculous example.

    But even more importantly, surely one should be very careful to distinguish between a normal process of science (crudely, puzzle solving, or "yet another discrepancy to be accounted for") and the neo-Popperian broadsides of Disney?
    Yes, it does, doesn't it?

    In a perfect world, oldman, how do you think such "fundamental soundness" should be ascertained?

    "chorus"? That's a joke, right? Two papers, over seven years apart, out of what, tens of thousands?

    "properly noticed"? I imagine "mainstream cosmologists", some of them anyway, read them and concluded that there's no meat ...

    But let's not jump the gun here, shall we? What do you think is the actual meat in each? Why not join the two threads actively discussing them?

    Myself I'm rather disappointed ... it seems that participants is this forum find it very difficult to focus on the actual content of these papers ...
     
  17. Nereid

    Nereid 4,014
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    I'm not sure if these are relevant to your points turbo-1, if not would you be kind enough to spell out where they miss the mark?

    They seem to address, at least in part, all the points you make in your post (that I am quoting), except for the quasar LF (I need to go over the Strauss video again, and do some searching).

    A semi-analytic model for the co-evolution of galaxies, black holes and active galactic nuclei:
    The Cosmological Evolution of Metal Enrichment in Quasar Host Galaxies:
     
  18. Nereid

    Nereid 4,014
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    Thanks for the reassurance.

    However, I went through the video, paying particular attention to each of the four points you made (per the OP of this thread).

    I did not hear Strauss make any of those points!

    I read the 100 slide PPT presentation that the website provides as "Supporting Material", looking specifically for where Strauss made any of the four points (in the OP).

    I did not see any slide which contains any of them!

    I'm sure you took careful notes when you viewed the video - you've cited it quite a few times, I think - so I'm pretty sure you felt you had a sound basis for your four points. May I ask you to review the notes you took as you watched the video, and write a few sentences on where Strauss made them?

    I'll comment on the rest of your post later.
     
  19. turbo

    turbo 7,366
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    I elaborated on point #1 to point out why the mass/luminosity of quasars must scale up as a function of the square of their separation from us. Strauss didn't get down to this level in his presentation since he was talking to a crowd of astronomers. It's a well-known relation.

    He talked in detail about every other point, including the unexplained running of the LF at z>3 AND talked about how this observation was posing problems for theorists. It's probably at about 50 min or so into the video - near the end.
     
  20. turbo

    turbo 7,366
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    When confronted by nay-saying on the Arp et al thread on BAUT, I took notes while re-watching Strauss' presentation and posted a time-line showing where he made these points. I'm sure you can find it.
     
  21. turbo

    turbo 7,366
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    My point is that even these excellent papers (among the best I found) have to strain theory and invoke some extreme coincidences to allow the existence of massive, metallized quasars at z~5-6. Not only must the accretion-rate problem be solved by invoking some fortuitous circumstances, the metallicity problem must be solved simultaneously by invoking another set of fortuitous circumstances. The second paper floats the possibility of a burst of star formation around z~7 to explain the high metallicity of quasars at z~6.5. Kind of an odd idea, since stars of high metallicity are expected to have much longer lifetimes than Pop III stars. Billions of years not 50 million years. I referenced these papers so you would have an idea what kinds of miracles would have to have happened to allow for the existence of high-redshift quasars in BB cosmology.
     
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