SDSS Quasars & Cosmology: Challenges to Current Models

[turbo]

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/

 

[Nereid]

[...]

Scroll down to Nov 2, 2005 and watch Michael Strauss' presentation to the Space Telescope Science Institute. [...]

http://www.stsci.edu/institute/itsd/...oquiaFall2005/

"Resource Not Found!"

Do you have a different source, a different URL perhaps?

 

[turbo]

"Resource Not Found!"

Do you have a different source, a different URL perhaps?

Evidently, the institute redesigned its site and my old bookmark no longer works. Here is a new one.

http://www.stsci.edu/institute/itsd/information/streaming/archive/STScIScienceColloquiaFall2005/

 

[Nereid]

(bold added)

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.

http://www.stsci.edu/institute/itsd/...oquiaFall2005/

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: http://cdsads.u-strasbg.fr/abs/2006AJ...131...49R". Here's the abstract (some formatting lost, bold added):

We report on i-band snapshot observations of 157 Sloan Digital Sky Survey quasars at 4.0<z<5.4 using the Advanced Camera for Surveys on the Hubble Space Telescope (HST) to search for evidence of gravitational lensing of these sources. None of the quasars appear to be strongly lensed and multiply imaged at the angular resolution (~0.1") and sensitivity of HST. The nondetection of strong lensing in these systems constrains the z=4-5 luminosity function to an intrinsic slope of β>-3.8 (3 σ), assuming a break in the quasar luminosity function at M*1450~-24.5. This constraint is considerably stronger than the limit of β>-4.63 obtained from the absence of lensing in four z>5.7 quasars. Such constraints are important to our understanding of the true space density of high-redshift quasars and the ionization state of the early universe.

IOW, normal science at work; no cherry picking, no suppression, ...

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

 

[turbo]

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.

 

[Nereid]

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.

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"

 

[Nereid]

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.

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?

 

[turbo]

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.

 

[Nereid]

(bold added)

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.

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.

 

[Nereid]

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?

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.

 

[turbo]

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.

 

[Nereid]

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.

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').

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.

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?

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.

Which theorists would that be? Names, etc.

Which theories would this have direct relevance to? Papers, etc.

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.

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.

 

[oldman]

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...Strauss points out ...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.

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.

 

[turbo]

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').

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.

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?

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.

Which theorists would that be? Names, etc.

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

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

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

 

[Nereid]

hi oldman, long time no see.

I do appreciate these sentiments. Well said.

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?

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.

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?

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.

Yes, it does, doesn't it?

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

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.

[...]

"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 ...

 

[Nereid]

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.

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).

http://fr.arxiv.org/abs/0808.1227":

We present a new semi-analytic model that self-consistently traces the growth of supermassive black holes (BH) and their host galaxies within the context of the LCDM cosmological framework. In our model, the energy emitted by accreting black holes regulates the growth of the black holes themselves, drives galactic scale winds that can remove cold gas from galaxies, and produces powerful jets that heat the hot gas atmospheres surrounding groups and clusters. We present a comprehensive comparison of our model predictions with observational measurements of key physical properties of low-redshift galaxies, such as cold gas fractions, stellar metallicities and ages, and specific star formation rates. We find that our new models successfully reproduce the exponential cutoff in the stellar mass function and the stellar and cold gas mass densities at z~0, and predict that star formation should be largely, but not entirely, quenched in massive galaxies at the present day. We also find that our model of self-regulated BH growth naturally reproduces the observed relation between BH mass and bulge mass. We explore the global formation history of galaxies in our models, presenting predictions for the cosmic histories of star formation, stellar mass assembly, cold gas, and metals. We find that models assuming the "concordance" LCDM cosmology overproduce star formation and stellar mass at high redshift (z>2). A model with less small-scale power predicts less star formation at high redshift, and excellent agreement with the observed stellar mass assembly history, but may have difficulty accounting for the cold gas in quasar absorption systems at high redshift (z~3-4).

http://fr.arxiv.org/abs/astro-ph/0309533":

We study the gas metallicity of quasar hosts using cosmological hydrodynamic simulations of the Lambda-cold dark matter model. Galaxy formation in the simulations is coupled with a prescription for black hole activity enabling us to study the evolution of the metal enrichment in quasar hosts and hence explore the relationship between star/spheroid formation and black hole growth/activity. We find a steep radial metallicity gradient in quasar host galaxies, with gas metallicities close to solar values in the outer parts but becoming supersolar in the center. The hosts of the rare bright quasars at z~5-6 have star formation rates of several hundred solar masses per year and halo masses of order ~10^12 solar masses. Already at these redshifts they have supersolar (Z ~2-3 solar) central metallicities, with a mild dependence of metallicity on luminosity, consistent with observed trends. The mean value of metallicity is sensitive to the assumed quasar lifetime, providing a useful new probe of this parameter. We find that lifetimes from 10^7-4x10^7yr are favored by comparison to observational data. In both the models and observations, the rate of evolution of the mean quasar metallicity as a function of redshift is generally flat out to z ~ 4-5. Beyond the observed redshift range and out to redshift z ~ 6-8, we predict a slow decline of the mean central metallicity towards solar and slightly subsolar values as we approach the epoch of the first significant star formation activity

 

[Nereid]

[...]

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

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

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.

 

[turbo]

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.

 

[turbo]

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?

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.

 

[turbo]

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).

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.

 

[Nereid]

I think I've tracked it down ...

[...]

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.

Here's my transcript of the key part of Strauss' presentation, starting at ~48:20 (bold added)

and we're showing this to our theorist colleagues, and they're saying "hmm, hmm, well that's interesting, I'm not sure that exactly fits into all our models", and so we're giving them a [?] hard time, which is the proper role [??]

The "this" is the second graph on slide 63 in the supporting material ("LF slope increases at z=3 and above").

The paper which reports these findings is (I think) http://fr.arxiv.org/abs/astro-ph/0601434" (bold added):

We determine the number counts and z=0-5 luminosity function for a well-defined, homogeneous sample of quasars from the Sloan Digital Sky Survey (SDSS). We conservatively define the most uniform statistical sample possible, consisting of 15,343 quasars within an effective area of 1622 deg^2 that was derived from a parent sample of 46,420 spectroscopically confirmed broad-line quasars in the 5282 deg^2 of imaging data from SDSS Data Release Three. The sample extends from i=15 to i=19.1 at z<3 and to i=20.2 for z>3. The number counts and luminosity function agree well with the results of the 2dF QSO Survey, but the SDSS data probe to much higher redshifts than does the 2dF sample. The number density of luminous quasars peaks between redshifts 2 and 3, although uncertainties in the selection function in this range do not allow us to determine the peak redshift more precisely. Our best fit model has a flatter bright end slope at high redshift than at low redshift. For z<2.4 the data are best fit by a redshift-independent slope of beta = -3.1 (Phi(L) propto L^beta). Above z=2.4 the slope flattens with redshift to beta=-2.37 at z=5. This slope change, which is significant at a >5-sigma level, must be accounted for in models of the evolution of accretion onto supermassive black holes.

IOW, the 'theorists' who were being given a hard time are those modelling "the evolution of accretion onto supermassive black hole", which is principally an astrophysics puzzle rather than a cosmology one.

Though this Richards et al. paper was published in 2006, it has already been cited over 100 times; among those citing it are papers by various theorists, proposing answers to the puzzle Strauss mentions in the video. For example:

http://fr.arxiv.org/abs/astro-ph/0603819":

We show that our previously proposed anti-hierarchical baryon collapse scenario for the joint evolution of black holes and host galaxies predicts quasar luminosity functions at redshifts 1.5<z<6 and local properties in nice agreement with observations. In our model the quasar activity marks and originates the transition between an earlier phase of violent and heavily dust-enshrouded starburst activity promoting rapid black hole growth, and a later phase of almost passive evolution; the former is traced by the submillimeter-selected sources, while the latter accounts for the high number density of massive galaxies at substantial redshifts z>1.5, the population of Extremely Red Objects, and the properties of local ellipticals.

http://fr.arxiv.org/abs/0706.1243":

(Abridged) We develop a model for the cosmological role of mergers in the evolution of starbursts, quasars, and spheroidal galaxies. Combining halo mass functions (MFs) with empirical halo occupation models, we calculate where major galaxy-galaxy mergers occur and what kinds of galaxies merge, at all redshifts. We compare with observed merger MFs, clustering, fractions, and small-scale environments, and show that this yields robust estimates in good agreement with observations. Making the simple ansatz that major, gas-rich mergers cause quasar activity, we demonstrate that this naturally reproduces the observed rise and fall of the quasar luminosity density from z=0-6, as well as quasar LFs, fractions, host galaxy colors, and clustering as a function of redshift and luminosity. The observed excess of quasar clustering on small scales is a natural prediction of the model, as mergers preferentially occur in regions with excess small-scale galaxy overdensities. We show that quasar environments at all observed redshifts correspond closely to the empirically determined small group scale, where mergers of gas-rich galaxies are most efficient. We contrast with a secular model in which quasar activity is driven by bars/disk instabilities, and show that while these modes probably dominate at Seyfert luminosities, the constraints from clustering (large and small-scale), pseudobulge populations, disk MFs, luminosity density evolution, and host galaxy colors argue that they must be a small contributor to the z>1 quasar luminosity density.

 

[Nereid]

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.

It might be useful to review the four points in the OP, as written:

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.

1) Indeed, Strauss did not say this.

For starters, the first part of the second sentence ("Because ...") contains some over-simplification (quasar absolute luminosities are estimates made by assuming a universe with certain (GR-based) parameters, and in these models luminosity does not "fall[] off as a function of the square of the distance (absent absorption)").

Slide 33 in the supporting material has some similarities with turbo-1's 1), but also some key differences ("cannibalizing host galaxies of over a trillion Solar masses" seems to be a turbo-1 addition, for example; and Strauss' "less than a billion years after the BB" became "a few hundred million years after the BB").

The video at ~22 minutes has the following (my transcription): "and I think it's fair to say that the theorists have not yet answered the question how that [the universe has managed to make such enormous black holes in such a short amount of time] might be possible; there are plausibility arguments, but only plausibility arguments so far about what might be going on."

What to make of these differences, in just one of the four points?

For example, does any reader think I'm being pedantic? or that turbo-1 has provided a significantly misleading summary?

...

It may be an interesting exercise to take a closer look at the statements at the end of the OP:

[...] 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.

For example, have those who publish papers in this field indeed not "changed their models to accommodate these observations"?

 

[turbo]

Nereid, the existence of ultra-massive, highly metallized quasars at z~6.5 is very much a problem for cosmology, not astrophysics. I assume you have some familiarity with how heavy elements up to and including iron are synthesized in the cores of stars through fusion. Iron is generally distributed through the explosions of type Ia SN. How can this be a problem for cosmology? The progenitors of such supernovae are white dwarf stars, which are the end-stage of intermediate-mass main-sequence stars. Such stars (like Sol) have lifetimes measured in billions of years. If quasars have super-Solar metallicity at z~6.5, as SDSS observations have shown, cosmologists must either push back the age of the BB universe (drastically) or discover another method that can create iron aside from fusion in stellar cores. Such fusion is inefficient because of iron's mass (it's at the limit of what a star can produce through fusion) and because of this, it is a very slow process.

Here is a very good review paper on the subject.

http://www.nhn.ou.edu/~cowan/nature04807.pdf

Although the general picture of element formation is understood, many questions about the nuclear physics processes and particularly the details of the supernova explosion mechanism remain to be answered. So the elements that are observed in the oldest stars were not synthesized internally, but instead are the result of ‘seeding’ from previous generations of stars. As the first generations of stars no longer exist, we suspect they must have been massive, but the details of their formation are not understood. This is particularly true because their compositions, devoid of elements except hydrogen and helium, make them different from stars like the Sun that have formed more recently. We can also tell something of the history of star formation in our Galaxy from the iron abundance, which astronomers refer to as ‘metallicity’. Most of the iron production that occurs today comes from type Ia supernovae. These result from the explosion of white dwarfs, formed from long-lived low-mass stars; thus, the stars that formed early in the history of the Galaxy and the Universe could not have had much iron. In our Galaxy these metal-poor stars are found in the (roughly spherical) halo, whereas the more metal-rich stars like the Sun reside in the flat galactic disk.

 

[Nereid]

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).

My point is that even these excellent papers (among the best I found)

First, thanks for the confirmation that the two papers I cited are, indeed, pertinent to the points you raise.

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.

I'm a little puzzled by this; some reasons:

* the observational results are relatively hot-off-the-press, and many details need confirming and/or filling in. If this field is typical of astronomy, we can expect to see several revisions over the next decade or two, resulting in an observational picture that has, at best, some important but nuanced differences from the one painted by Strauss in the video

* cosmologically-relevant conclusions depend upon a whole slew of observational and (non-cosmological) theoretical dragons being slain, or at least tamed. Observationally, the selection effects certainly in play were far from understood in 2005 (and are still not well characterised), to take one example. Theoretically, understanding of the importance of the key physical processes involved in baryonic matter evolution from z ~1000 to ~7 was very poor in 2005 (and remains so today), which means that models are far from robust

* despite the above, good progress has been made; for example in recognising that mergers and AGN feedback were likely very efficient means of triggering furious star formation (mega-starbursts)

* less than half a decade has passed since the release of SDSS DR3 (the backdrop to Strauss' presentation), which is a very short time (about the time it takes to do a PhD, for example).

Thus it's surely far too early to declare the circumstances 'fortuitous', isn't it?

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.

This is a good example of some of things I have just mentioned.

Without any 'ground truth', in the form of actual Pop III stars, stellar evolution models must surely have big caveats attached. Also, the stellar IMF in environments that later became home to the observed z ~6 quasars is similarly poorly constrained. Finally, it seems that there may be some strong positive feedback loops in those (proto-) high-z quasar environments.

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.

And I thank you for that.

However, it seems we have reached very different conclusions ... to you they shout 'miracles needed here!'; to me it's just normal science (miracles not applicable).

 

[turbo]

It puzzles me that you can blithely accept the observation of highly metallized bodies at z~6.5 in light of the earlier expectations for redshift-dependent evolution in absolute and relative metallicity in quasars. The expectations were not met - to the contrary z~6.5 quasars look just like local ones, except that the LF curve runs away after z>3.

To someone convinced in the infallibility of the BB model, it might be understandable to try to fit these monsters into the theory somehow, regardless how implausible the mechanisms invoked. I hope that we get beyond this mind-set collectively, somehow. SDSS has shown us some outstanding things, especially about AGN and QSOs, so it shouldn't be "business as usual" for cosmology.

 

[Nereid]

There are already lots of well-known strange features of quasars, such as luminosities which are hard to explain by any theory and which apparently evolve throughout the life so far of the universe in a way which requires multiple parameters to explain (and imply that quasars have conveniently "turned off" recently). There are also of course Arp's observations that most of the brightest quasars fall into lines either side of a particular type of galaxy, where the closest ones have high relative redshifts but the most distant ones have similar redshifts to the central galaxy, and there are often hydrogen clouds scattered along the same lines. The new information about the metallicities of high-redshift quasars which turbo-1 referenced in the opening post of this thread adds to this pattern. Perhaps no one point proves anything, but all of this strongly suggests that a simpler explanation would be that some of the redshift is intrinsic.

The gravitationally lensed quasar case is the one referenced in the "Black Holes or MECO" paper by R Schild of which a preprint is available at http://arxiv.org/abs/0806.1748" , where he presents evidence for a strong magnetic field between the quasar and the surrounding material. I cannot comment on the strength of this evidence. However, it is well known that a black hole cannot have a strong intrinsic magnetic field because of the "no hair" theorem, because the only charge it can contain is unbalanced charge (which tends to self-neutralize anyway by preferentially attracting oppositely-charged matter), and the circulation of that in a rotating black hole cannot create any significant magnetic field at all.

The apparent magnetic field of the gravitationally lensed quasar is used as evidence in support of the "MECO" (magnetospherical eternally collapsing object) theory of Abhas Mitra and others, but I don't find that plausible. Instead, I think it's a lot simpler and black holes are an artefact of Hilbert simplifying the maths without realizing the implications, as described by Salvatore Antoci and others in a paper "Reinstating Schwarzschild's Original Solution" of which there is a preprint at http://arxiv.org/abs/gr-qc/0406090" .

Within GR black hole theory it is possible for a small amount of intrinsic redshift to arise from the gravitational redshift of the inner edge of an accretion disk at the closest stable orbit. However, this effect is not capable of giving rise to the sort of intrinsic redshift that would be needed to adjust the apparent distances of the brightest quasars to make them more uniformly distributed, nor to make them match the redshifts of the apparent host galaxies according to Arp. This is a well-known argument which has been used as the basis for the standard claim that Arp's observations must be coincidences because GR doesn't allow intrinsic redshift at that level.

I hope that discussions on the validity of the original Schwarzschild solution will resume eventually on the S&GR forum, if and when George Jones permits it. That topic is quite tricky, as Schwarzschild's initial assumption of a point mass is seriously unphysical and does very nasty things to coordinates, and I've been having a lot of difficulty understanding it. However, what shocked me most about the topic is that it appears that the standard answer to any question relating to the relevant physics or mathematics (on these forums or anywhere else) seems to be defensiveness, anger and abuse.

The point about the Schwarzschild radial coordinate is not the point here, anyway. I mainly wish to show strong agreement with the idea that the official ideas about quasars seem increasingly contrived and that it is surely time to investigate alternatives, starting from what we actually see. Arp's observations are very convincing (unlike his theories) - nearly ALL the known bright quasars line up across "host" galaxies and have red shifts where the closest quasars to the host galaxy have the largest difference in red shifts and appear to be the most active, and the further ones look more like galaxies and have similar redshifts to the "host" galaxy.

Although GR is very neat, and has been experimentally verified in the solar system to high accuracy, as I become more familiar with it I am becoming quite sceptical about it, and I feel it's probably just another approximation. In particular, if you look at the neat ideas in Dennis Sciama's 1953 "Origin of Inertia" paper http://adsabs.harvard.edu/abs/1953MNRAS.113...34S" where inertia and rotational effects arise naturally and trivially from the gravitational effect of the universe by analogy with electromagnetism, fully satisfying Mach's principle, it's very disturbing and dissatisfying that GR can be proved to be theoretically incompatible with Mach's principle (as Einstein demonstrated) while at the same time showing frame-dragging effects of exactly the right order of magnitude.

I therefore think GR should be treated like other physical theories as a work in progress, rather than being given what appears to be disproportionate reverence. However, this doesn't seem to be possible. Perhaps GR is such a mathematical subject that the people who study it are mostly mathematicians rather than physicists.

I'm now planning to try to learn more about detailed quasar spectral features, to see whether they perhaps fit the idea of an object with a relativistically spinning surface better than an accretion disk.

Jonathan, I asked you to start a new thread if you want to discuss Arp, quasar intrinsic redshifts, etc.

I also asked you to discuss GR-related aspects in the S&GR section.

Would you be kind enough to say why you chose, instead, to hijack this thread?

 

[matt.o]

Nereid, the existence of ultra-massive, highly metallized quasars at z~6.5 is very much a problem for cosmology, not astrophysics. I assume you have some familiarity with how heavy elements up to and including iron are synthesized in the cores of stars through fusion. Iron is generally distributed through the explosions of type Ia SN. How can this be a problem for cosmology? The progenitors of such supernovae are white dwarf stars, which are the end-stage of intermediate-mass main-sequence stars. Such stars (like Sol) have lifetimes measured in billions of years. If quasars have super-Solar metallicity at z~6.5, as SDSS observations have shown, cosmologists must either push back the age of the BB universe (drastically) or discover another method that can create iron aside from fusion in stellar cores. Such fusion is inefficient because of iron's mass (it's at the limit of what a star can produce through fusion) and because of this, it is a very slow process.

Here is a very good review paper on the subject.

http://www.nhn.ou.edu/~cowan/nature04807.pdf

Firstly, this argument smacks of the "God of the gaps" used by creationists to undermine evolution. i.e. we don't understand high metallicity quasars, therefore LCDM cosmology must be wrong!

Also, this quote:

Most of the iron production that occurs today comes from type Ia supernovae.

does not back up your argument regarding the production of iron. I have emboldened the appropriate word in your quotation to show this. The word "most" certainly does not mean "all". Those who bothered to open your link will also have noticed how you cherry picked your quoted paragraph so it excluded the initial sentences, which were:

More massive stars evolve at a much faster rate and typically live only
millions of years. During the last brief period of their lives they undergo
titanic supernova explosions. It is during this explosion that the r-process
elements (such as platinum and gold) are ejected into interstellar
gas that will eventually form new stars.

To me, the problem is one of galaxy evolution at early times, i.e., tying down the initial mass function, the properties of the first stars, etc. etc. Future observations will be capable of solving these dilemmas.

 

[Nereid]

Nereid, the existence of ultra-massive, highly metallized quasars at z~6.5 is very much a problem for cosmology, not astrophysics.

I guess we'll just have to differ on this, at least for now, won't we?

To restate: unless and until at least the key details of the physical processes that may have been at work, from z~1000 to ~6, have been identified and at least crudely modeled, how can anyone tell that this is not, principally, an astrophysics puzzle?

I assume you have some familiarity with how heavy elements up to and including iron are synthesized in the cores of stars through fusion. Iron is generally distributed through the explosions of type Ia SN. How can this be a problem for cosmology? The progenitors of such supernovae are white dwarf stars, which are the end-stage of intermediate-mass main-sequence stars. Such stars (like Sol) have lifetimes measured in billions of years. If quasars have super-Solar metallicity at z~6.5, as SDSS observations have shown, cosmologists must either push back the age of the BB universe (drastically) or discover another method that can create iron aside from fusion in stellar cores. Such fusion is inefficient because of iron's mass (it's at the limit of what a star can produce through fusion) and because of this, it is a very slow process.

Here is a very good review paper on the subject.

http://www.nhn.ou.edu/~cowan/nature04807.pdf

Although the general picture of element formation is understood, many questions about the nuclear physics processes and particularly the details of the supernova explosion mechanism remain to be answered. So the elements that are observed in the oldest stars were not synthesized internally, but instead are the result of ‘seeding’ from previous generations of stars. As the first generations of stars no longer exist, we suspect they must have been massive, but the details of their formation are not understood. This is particularly true because their compositions, devoid of elements except hydrogen and helium, make them different from stars like the Sun that have formed more recently. We can also tell something of the history of star formation in our Galaxy from the iron abundance, which astronomers refer to as ‘metallicity’. Most of the iron production that occurs today comes from type Ia supernovae. These result from the explosion of white dwarfs, formed from long-lived low-mass stars; thus, the stars that formed early in the history of the Galaxy and the Universe could not have had much iron. In our Galaxy these metal-poor stars are found in the (roughly spherical) halo, whereas the more metal-rich stars like the Sun reside in the flat galactic disk.

Kinda makes my case doesn't it?

Although the general picture of element formation is understood, many questions about the nuclear physics processes and particularly the details of the supernova explosion mechanism remain to be answered.

"Most of the iron production that occurs today comes from type Ia supernovae."

Are you saying that the theoretical work is now so complete and far-ranging that the only significant iron production in the environments of (proto-)AGNs can be type Ia SNe?

ETA: I see that matt.o responded while I was writing my post; interesting independent comments, don't you think?

 

[Nereid]

I'll come back to the content here later, but there's an interesting change that I note in the course of this thread ...

It puzzles me that you can blithely accept the observation of highly metallized bodies at z~6.5 in light of the earlier expectations for redshift-dependent evolution in absolute and relative metallicity in quasars. The expectations were not met - to the contrary z~6.5 quasars look just like local ones, except that the LF curve runs away after z>3.

To someone convinced in the infallibility of the BB model, it might be understandable to try to fit these monsters into the theory somehow, regardless how implausible the mechanisms invoked. I hope that we get beyond this mind-set collectively, somehow. SDSS has shown us some outstanding things, especially about AGN and QSOs, so it shouldn't be "business as usual" for cosmology.

From the OP (bold added):

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.

Dozens, even hundreds, of papers written in this period, many of them by theorists and (by turbo-1's definition) cosmologists*.

In short, no lack of empirical, objective evidence that this is a really hot research topic in astronomy/astrophysics/cosmology today!

* a tiny handful of which have been cited in this thread.

 

[turbo]

Dozens, even hundreds, of papers written in this period, many of them by theorists and (by turbo-1's definition) cosmologists*.

In short, no lack of empirical, objective evidence that this is a really hot research topic in astronomy/astrophysics/cosmology today!

* a tiny handful of which have been cited in this thread.

Have you seen any papers in peer-reviewed journals that explain how the z~6.5 quasars can be so highly metallized, and show no evolution with redshift, no lensing, and a soaring LF at z>3? I haven't. If solving these puzzles within BB cosmology is not possible, what are the options for cosmology? Would a spatially and temporally infinite universe solve the problem? If not, why not?

At this time, all SDSS observations >z~5.7 are single-band detections, so when Webb comes on-line, I fully expect that it IR capabilities will allow observation of even more highly redshifted quasars. At what point will concordance cosmologists say, "Gee, we really have to rethink the BB. The BB model is not capable of being modified to the point at which these quasars can be accommodated."? Where? z~7, 7.5, 8? At what redshift do quasars falsify the BB? Not constrain it to implausibility but kill it.

 

[Nereid]

[...]

At this time, all SDSS observations >z~5.7 are single-band detections, so when Webb comes on-line, I fully expect that it IR capabilities will allow observation of even more highly redshifted quasars. At what point will concordance cosmologists say, "Gee, we really have to rethink the BB. The BB model is not capable of being modified to the point at which these quasars can be accommodated."? Where? z~7, 7.5, 8? At what redshift do quasars falsify the BB? Not constrain it to implausibility but kill it.

Have you had a chance to read this preprint:

http://arxiv.org/abs/0812.3950"

We study the prospects of finding the first quasars in the universe with ALMA and JWST. For this purpose, we derive a model for the high-redshift black hole population based on observed relations between the black hole mass and the host galaxy. We re-address previous constraints from the X-ray background with particular focus on black hole luminosities below the Eddington limit as observed in many local AGN. For such luminosities, up to 20% of high-redshift black holes can be active quasars. We then discuss the observables of high-redshift black holes for ALMA and JWST by adopting NGC 1068 as a reference system. We calculate the expected flux of different fine-structure lines for a similar system at higher redshift, and provide further predictions for high-J CO lines. We discuss the expected fluxes from stellar light, the AGN continuum and the Lyman $\alpha$ line for JWST. Line fluxes observed with ALMA can be used to derive detailed properties of high-redshift sources. We suggest two observational strategies to find potential AGN at high redshift and estimate the expected number of sources, which is between 1-10 for ALMA with a field of view of $\sim(1')^2$ searching for line emission and 100-1000 for JWST with a field of view of $(2.16')^2$ searching for continuum radiation. We find that both telescopes can probe high-redshift quasars down to redshift 10 and beyond, and therefore truly detect the first quasars in the universe.

(more later)

 

[turbo]

Have you had a chance to read this preprint:

http://arxiv.org/abs/0812.3950"
(more later)

Yes, and others of a similar nature. JWST probably won't be used as a survey instrument, so such finds may be serendipitous, at least in the first phases of operation.

 

[Nereid]

Have you seen any papers in peer-reviewed journals that explain how the z~6.5 quasars can be so highly metallized, and show no evolution with redshift, no lensing, and a soaring LF at z>3? I haven't. If solving these puzzles within BB cosmology is not possible, what are the options for cosmology?

Indeed.

But as matt.o pointed out (as did I), what makes this an essentially LCDM cosmological puzzle?

What is the source of your confidence that boring old astrophysics has been shown incapable of addressing any aspect of this, to a degree that might, just might, hint that any cosmological aspects are rather minor? that such boring astrophysics cannot - even in principle - contribute to understanding these puzzles in any meaningful way?

In the fashion of reductionism in science - which has a long and extremely good track record - maybe it just might, perhaps, be possible to address this by tackling just one part at a time? Whence comes urgency of tackling all aspects simultaneously?

Would a spatially and temporally infinite universe solve the problem? If not, why not?

[...]

Who knows?

If you do, why not write up your research and get it published?

If not, what classes of "spatially and temporally infinite universe" models would you suggest should be examined (and why)?

Would you regard it as important that any such models be required to also, within a year or five, adequately address the entirety of the observational results that LCDM models seem to be able to (many aspects of the CMB, light nuclide abundances, LSS, BAO, etc, etc)?

 

[Nereid]

[...]

At this time, all SDSS observations >z~5.7 are single-band detections, [...]

OK ... but so what?

There are plenty of papers presenting observational results of non-SDSS z>~5.7 quasars (or lack thereof), and didn't Strauss cover this (to some extent) in the video you cited? IIRC, he reported some sobering constraints, in terms of (then) contemporary understanding of z > 6 quasar populations (cf individual objects) ...

 

[turbo]

Indeed.

But as matt.o pointed out (as did I), what makes this an essentially LCDM cosmological puzzle?

Any model must not only explain observations, but admit to falsification by those observations.

What is the source of your confidence that boring old astrophysics has been shown incapable of addressing any aspect of this, to a degree that might, just might, hint that any cosmological aspects are rather minor? that such boring astrophysics cannot - even in principle - contribute to understanding these puzzles in any meaningful way?

In the fashion of reductionism in science - which has a long and extremely good track record - maybe it just might, perhaps, be possible to address this by tackling just one part at a time? Whence comes urgency of tackling all aspects simultaneously?

The puzzles (anomalous observations) cannot be solved in a vacuum, one at a time. There are many adjustable parameters in cosmology that can be tweaked to "allow" the fitting of one observation or another (at least to the satisfaction of a BB adherent), even if the proposed fix is implausible and/or unsupported by any evidence.

Who knows?

If you do, why not write up your research and get it published?

I'm already involved in another paper with Ari and Dave (and another co-conspirator) and expect to have it published in the same journal as the last one. I don't have time to become a cosmologist right now, nor the inclination to try to get published as one, as long as the field is dominated by BB/LCDM

If not, what classes of "spatially and temporally infinite universe" models would you suggest should be examined (and why)?

Would you regard it as important that any such models be required to also, within a year or five, adequately address the entirety of the observational results that LCDM models seem to be able to (many aspects of the CMB, light nuclide abundances, LSS, BAO, etc, etc)?

LCDM seems to be able to accommodate many things (retro-dictions, not predictions) in part because there are so many parameters that can be tweaked.

If Fotini Markopoulou is right, and we see frequency-dependent delays in the arrival times of Gamma rays (more energetic=slower) then we will have a reason to consider space a transmissive medium with variable optical characteristics. That would shake things up and might help make cosmology a more exact science. Waiting for that.