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William
2007-Sep-27, 02:55 AM
This is an interesting paper “On the Evolution of High-Red Shift Quasars” by Xiaohui Fan. Does anyone have any answers to the questions poised by Fan based on the quasar data?

http://sait.oat.ts.astro.it/MSAIt770206/PDF/2006MmSAI..77..635F.pdf


The last few years has witnessed the discovery of luminous quasars at z > 6, which are likely anchored by supermassive black holes with > 10^9 M_. Furthermore, the spectral energy distribution of these quasars, across the entire electromagnetic spectrum, shows very little evolution from their low-redshift counterparts. Is the existence of luminous quasars, with massive black holes and “mature” SEDs and high metallicity a big surprise? Or this is something totally expected?

Are there any theories that explain why the quasar's spectrum does not evolve with the cosmos?


– In sharp contrast to the strong density evolution is the lack of strong evolution of quasar spectral properties. The strength Fan: High-redshift Quasars 637 of emission lines remains roughly constant through cosmic history. The immediate environment of quasars matures very early on, and are somewhat decoupled from the cosmic evolution. In other words, quasar emission looks the same even up to the highest redshift, which implies that the knowledge about quasar emission we learned from local universe can be applied to the highest redshift.


Are there any theories to explain why there is supersolar metallicity in high redshift quasars?


- The sample of quasars at z > 5:7 from the SDSS provides the first opportunity to study the evolution of quasar spectral properties at z approx. 6, less than 1 Gyr after the Big Bang and only 700 million years from the first star formation in the Universe. Optical and infrared spectroscopy of some z approx. 6 quasars already indicates a lack of evolution in the spectral properties of these luminous quasars: Pentericci et al. (2002) show that the CIV/NV ratio in two z approx. 6 quasars are indicative of supersolar metallicity in these systems.


Black holes are believed to grow by accretion. What mechanism could limit there growth to 10^10 solar masses? Fan also notes that the size of black holes in the early universe is pushing the maximum theoretical accretion rate, based on time available from the standard cosmological model.


One intriguing feature that we noticed is the apparent lack of quasars with BH masses larger than a few times 10^10 solar masses, at all redshift.

William
2007-Sep-27, 03:19 AM
This paper by Hawkins is also interesting. Quasars should show time dilation based on distance. Other time variant cosmological objects do exhibit time dilation, with distance, which of course supports the assertion that the Universe is expanding and SR is not falsified.

Quasars do not exhibit time dilation, according to the data and analysis in Hawkins attached paper. Was anyone seen an explanation for this anomaly? I could not find an explain in the forums or any subsequent paper, that refuted Hawkins' data or/and conclusion.

arXiv:astro-ph/0105073 v1 4 May 2001

"Time Dilation and Quasar Variability" by M. R. S. Hawkins University of Edinburgh, Royal Observatory.

ABSTRACT
The timescale of quasar variability is widely expected to show the effects of time dilation. In this paper we analyse the Fourier power spectra of a large sample of quasar light curves to look for such an effect. We find that the timescale of quasar variation does not increase with redshift as required by time dilation. Possible explanations of this result all conflict with widely held consensus in the scientific community.

Cougar
2007-Sep-27, 03:55 PM
This paper by Hawkins is also interesting. Quasars should show time dilation based on distance. Other time variant cosmological objects do exhibit time dilation, with distance, which of course supports the assertion that the Universe is expanding and SR is not falsified.

Quasars do not exhibit time dilation, according to the data and analysis in Hawkins attached paper. Was anyone seen an explanation for this anomaly? I could not find an explain in the forums or any subsequent paper, that refuted Hawkins' data or/and conclusion.

arXiv:astro-ph/0105073 v1 4 May 2001

"Time Dilation and Quasar Variability" by M. R. S. Hawkins University of Edinburgh, Royal Observatory.

There has been some argument about this paper here at BAUT. Here is the problem I have with it:

Quasars vary in luminosity on a variety of time scales. Some vary in brightness every few months, weeks, days, or hours. If there was some consistency in quasar luminosity variation, then one could use that variation to test for time dilation as it correlates to the measured redshift. But there is no such consistency, so how does one use inconsistent luminosity variation to claim "no time dilation in quasars"?

Well, I haven't read Hawkins' paper recently, but as I recall, he uses a statistical argument. But in the history of the universe, quasars exhibit a pretty clear evolution - there used to be a lot of them, there is a peak era of quasar activity, and there are none around "today." One certainly cannot assume that quasar activity has remained constant throughout the history of the universe. Was this evolution factored into Hawkins' statistical analysis?

Nereid
2007-Sep-27, 04:06 PM
This paper by Hawkins is also interesting. Quasars should show time dilation based on distance. Other time variant cosmological objects do exhibit time dilation, with distance, which of course supports the assertion that the Universe is expanding and SR is not falsified.

Quasars do not exhibit time dilation, according to the data and analysis in Hawkins attached paper. Was anyone seen an explanation for this anomaly? I could not find an explain in the forums or any subsequent paper, that refuted Hawkins' data or/and conclusion.

arXiv:astro-ph/0105073 v1 4 May 2001

"Time Dilation and Quasar Variability" by M. R. S. Hawkins University of Edinburgh, Royal Observatory.There's a 2007 paper by Hawkins (http://adsabs.harvard.edu/abs/2007A%26A...462..581H) that puts his earlier one (that you cite, William) in a better context:
This paper sets out to measure the timescale of quasar variability with a view to new understanding of the size of accretion discs in active galactic nuclei. Previous attempts to measure such timescales have been based on sparsely sampled data covering small ranges of time. Here we combine data from two large scale monitoring programmes to obtain Fourier power spectra of light curves covering nearly three orders of magnitude in frequency in blue and red passbands. If the variations are interpreted as due to gravitational microlensing, then timescale measurements in the observer's frame imply a minimum mass for the microlensing bodies of around 0.4~Mȯ. On the assumption that the variations are intrinsic to the quasars, a correction must be made for time dilation. In this case the power spectrum shows a break corresponding to a timescale of about 11 years. This timescale is used to measure the size of the accretion disc, which is found to be about 10-2 pc or 10 light days, in agreement with limits set by self-gravitation and coincident with the broad line region of the active galactic nucleus. It is suggested that the broad line region may be associated with the break up of the outer part of the accretion disc.To look at this at the soundbite level, quasars are composite objects (accretion disk, dust torus, jet, broad-line region, etc) which seem to come in several distinctly different kinds, and which seem to have evolved over cosmic time. Thus not a good class of object to use to test time dilation.

William
2007-Sep-28, 12:25 AM
In reply to Neried’s comment:


To look at this at the soundbite level, quasars are composite objects (accretion disk, dust torus, jet, broad-line region, etc) which seem to come in several distinctly different kinds, and which seem to have evolved over cosmic time. Thus not a good class of object to use to test time dilation.


The question is not whether time dilation does or does not occur for other cosmological objects, for increasing redshift. It does, occur, for example for SN1a. Time dilation does not occur for quasars for increasing redshift, based on Hawkins’ observations and analysis, which is not explained. There is no paper refuting Hawkins data or analysis.

The data and analysis shows that quasars do not show time dilation and do not show evolution of metallicity, with increasing redshift. The two observations are mutually supportive. Lack of evolution of metallicity also needs an explanation. I have not found any papers that explain the lack of evolution of metallicity in the quasar spectrum or papers that refute Hawkins findings. I believe there is not an issue with the measurement of spectral metallicity in quasars.

In Reply to Cougar’s comment:


But in the history of the universe, quasars exhibit a pretty clear evolution - there used to be a lot of them, there is a peak era of quasar activity, and there are none around "today." One certainly cannot assume that quasar activity has remained constant throughout the history of the universe. Was this evolution factored into Hawkins' statistical analysis?

See figure 3 in Fan’s attached paper, density Vs redshift. Quasar density certainly does evolve. The problem is there is no physical explanation why quasar density should be following this profile. And why are there no highly luminous quasars at z=0? Are there galaxy mergers at z=0? There is dust & large black holes at z=0. Would wouldn’t that plus merger produce a highly luminous quasar during the merger? I have found no papers that explain this anomalous evolution of quasar density.


http://sait.oat.ts.astro.it/MSAIt770206/PDF/2006MmSAI..77..635F.pdf

William
2007-Sep-28, 03:29 AM
In reply to Nereid: There's a 2007 paper by Hawkins that puts his earlier one (that you cite, William) in a better context:


http://arxiv.org/pdf/astro-ph/0611491

Nereid, further on in the 2007 Hawkins' paper “Timescale of variation and the size of the accretion disc in active galactic nuclei” Hawkins notes that the new data strongly supports the finding in his 2001 paper that quasars do not exhibit time dilation.

From the 2007 Paper:


After the first primitive estimates of timescale discussed in the Introduction, and when the Fourier power spectrum was plotted in the form of a log/log plot, it was clear that there was no obvious break in a linear relation. This situation persisted as more data was added, and it was in this context that the short term MACHO data was added as the only realistic way of extending the baseline. It is quite remarkable that for the case of the observer’s reference frame the straight line relationship was maintained, covering three orders of magnitude in time and reinforcing the result of Hawkins (2001).

William
2007-Sep-28, 02:55 PM
The link in the above comment, to Hawkins’ paper, which presents evidence that quasars do not exhibit time dilation with redshift, was faulty. Here is a working link to the paper.

http://arxiv.org/pdf/astro-ph/0105073

Nereid
2007-Sep-28, 03:20 PM
http://arxiv.org/pdf/astro-ph/0611491

Nereid, further on in the 2007 Hawkins' paper “Timescale of variation and the size of the accretion disc in active galactic nuclei” Hawkins notes that the new data strongly supports the finding in his 2001 paper that quasars do not exhibit time dilation.

From the 2007 Paper:Indeed.

And what you do with the observations is what makes science.

What Hawkins did, in the 2007 paper, was present an explanation that is both internally consistent and consistent with the current consensus on what the nature of quasars (AGNs) is - an accretion disk around an SMBH (plus jet, plus ...).

Further, from that analysis, he developed a model which seems to provide a new insight into a feature or two of the accretion disk and broad line region.

Or, crudely, the apparent lack of a time dilation signal in observations of quasar variability can be rather nicely explained within the mainstream, consensus, view of quasars.

Or, to answer the question you asked in post #2 ("[H]as anyone seen an explanation for this anomaly?"): Yes, Hawkins himself has published a paper with just such an explanation.

Would you be interested to explore the 2007 Hawkins paper further (which would involve doing more than just copying and pasting some juicy bits)?

Cougar
2007-Sep-28, 04:45 PM
The data and analysis shows that quasars do not show... evolution of metallicity, with increasing redshift.... Lack of evolution of metallicity also needs an explanation. I have not found any papers that explain the lack of evolution of metallicity in the quasar spectrum...

The following article appears to contain some of the explanation you seek:

Quasar Elemental Abundances at High Redshifts, (http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v589n2/57293/57293.html?erFrom=-611561731304642315Guest)
M. Dietrich, F. Hamann, J. C. Shields, A. Constantin, J. Heidt, K. Jäger, M. Vestergaard, and S. J. Wagner
The Astrophysical Journal, 589:722-732, 2003 June 1, 2003.


In the context of galaxy evolution, the conditions that give rise to quasars and massive black holes will also yield solar or supersolar metallicities on timescales shorter than ∼1 Gyr (Arimoto & Yoshii 1987; Hamann & Ferland 1993; Gnedin & Ostriker 1997; Friaça & Terlevich 1998; Cen & Ostriker 1999; Romano et al. 2002). Additional strong evidence for the relationship between quasar activity, host galaxy formation, and intense star formation episodes is provided by the detection of large amounts of dust (∼108 Msolar) and molecular gas (∼1010 Msolar) measured in high-redshift quasars (Andreani, La Franca, & Cristiani 1993; Isaak et al. 1994; Omont et al. 1996, 2001; Carilli et al. 2000, 2001).

William
2007-Sep-28, 05:40 PM
Thanks for the link Cougar.


The following article appears to contain some of the explanation you seek:

Quasar Elemental Abundances at High Redshifts,
M. Dietrich, F. Hamann, J. C. Shields, A. Constantin, J. Heidt, K. Jäger, M. Vestergaard, and S. J. Wagner
The Astrophysical Journal, 589:722-732, 2003 June 1, 2003.


The question was: How can the absolute lack of any evolution (change) of the metallicity in the quasar spectrum z=0 to z=2.5 be explained? The spectrum of quasars at z=2.5,2.4,2.3, and so forth is identical to z=0.1 expect for the redshift changes in the spectrum. And (another problem) at high z, say z=4 and greater, the quasar spectrum then starts to shows evidence of super solar metallicity. (i.e. Greater metallicity in the quasar spectrum than at z=0.)

The above paper states that special conditions in the early universe, could have produced an abundance of super large stars. The super large stars when they exploded could have created the super solar metallicity conditions, in the early galaxies and in the vicinity of the quasars.

The super large stars need to be close to the early universe quasars which I believe is a theoretical problem. I thought the standard cosmological model had quasars forming first, then AGN with stars. Did quasars co-exist with the first stars? I have been researching super large stars and I believe the evidence does not support the above paper's hypothesis, for the early universe or for any other time for that matter. i.e. Super large stars are rare and their evolutionary cycle does not produce the required metallicity. (If it is OK, perhaps later a separate thread could be started to discuss super large stars, metallicity evolution, and the early universe.)

Also the above paper does not address the question, why would metallicity remain constant for increasing z, to z=2.5 and then increase for high z? There is still the problem of z=0 to z=2.5 during which quasar spectrum does not evolve.

William
2007-Sep-28, 05:49 PM
Early universe quasar engine issue? Super black hole at z=5 formation problem.

Fan notes in his paper “Evolution of High Redshift Quasars” (link below) that for quasars to exist at z=5, there must be a mechanism to create super massive black holes at z=5. Fan states that very rapid formation of a super massive black hole requires a large seed black hole, of 100 solar masses, to have formed with the first stars. If the seed black holes is too small, the super massive black hole can not formed by z=5.


Assuming continuous Eddington accretion from a seed black hole of 100 M, the formation redshift for seed black holes must be at z > 10. Even with continuous accretion, black holes in the most luminous quasars barely had enough time growing. While there are various ways of accreting faster than Eddington, the fact that the highest redshift quasars sit right at the threshold of the reionization epoch simply indicate that the initial growth of those BHs have to be very efficient and very early on.


http://sait.oat.ts.astro.it/MSAIt770206/PDF/2006MmSAI..77..635F.pdf


The problem is there is no evidence at z=0 of any large none galactic centre black holes. The largest black hole in the Milky Way is 14 M +/-4M. Does the finding that there are no 100M solar mass black holes at z=0, indicate that there is no mechanism to create black holes of 100 solar mass at z=0 or at z=10?

Others have noted the “Early Quasar seed problem”. The follow is an excerpt from a paper that discusses the observations at z=0 in the Milky Way and a microquasar review paper that states the problem.

http://arxiv.org/pdf/astro-ph/0701837


The microquasar GRS 1915+105 has been extensively observed since this source is known to be extremely variable at all wavelengths (see Fuchs et al. 2003 for a review). It hosts the most massive known stellar mass black hole of our Galaxy with M = 14 ±4M⊙ (Greiner et al. 2001a)


This review paper on microquasars asks the seed black hole question: Why are there no large black holes observed in the Milky Way or in the Magellanic Clouds?

"Microquasars: Progress and Open Questions" by I.Mirabel

http://arxiv.org/pdf/astro-ph/0701837

2) If black holes of intermediate mass (≥ 100 M) are prolific, why has no one been identified in the Milky Way or the Magellanic Clouds, where the dynamical mass of compact objects in binaries can be determined ?

neilzero
2007-Sep-28, 06:41 PM
If we find 1000 quasars in 10^30 cubic light years of space about 13 billion light years from Earth: we should expect to find 100 quasers in 10^29 cubic light years:10 quasars in 10^28 cubic light years 1+ or - 1 in 10^27 cubic light years; None in a volume of 10^26 cubic light years, etc
Unless quasers occur lots more often the last 400 million years compared to about 11 billion years ago, why would we expect to find any quasars close to Earth or even 400 million light years from Earth, or is my arithmetic flawed? There is only about 10^26 cubic light years within 400 million light years of Earth. Neil

Cougar
2007-Sep-28, 08:50 PM
The above paper states that special conditions in the early universe could have produced an abundance of super large stars. The super large stars when they exploded could have created the super solar metallicity conditions, in the early galaxies and in the vicinity of the quasars.

Remember that average gas density increases as (1+z)3. At larger z, I would think that this could certainly be considered "special conditions."

William
2007-Sep-28, 11:37 PM
In reply to Cougar's comment:


Remember that average gas density increases as (1+z)^3. At larger z, I would think that this could certainly be considered "special conditions."

Does the cloud gas density increase or does the density of the number of gas clouds increase? How does one answer this question observationally?

Do the gas clouds clump via gravitational forces? I do not understand why a gas cloud at z=0 is different than a gas cloud at z=2.5 which is when quasars are at their highest density.

Comment:
As I said, I believe there is new work and findings concerning the life cycle of very large stars which is relevant to this specific discussion (what are the products of a large star produced during its cycle), but I have not had a chance to read through the new papers.

William
2007-Sep-28, 11:52 PM
In reply to zeroneil’s comment.



If we find 1000 quasars in 10^30 cubic light years of space about 13 billion light years from Earth: we should expect to find 100 quasers in 10^29 cubic light years:10 quasars in 10^28 cubic light years 1+ or - 1 in 10^27 cubic light years; None in a volume of 10^26 cubic light years, etc Unless quasars occur lots more often the last 400 million years compared to about 11 billion years ago, why would we expect to find any quasars close to Earth or even 400 million light years from Earth, or is my arithmetic flawed? There is only about 10^26 cubic light years within 400 million light years of Earth.

Zeroneil, the quasar density evolves/changes with redshift.


There are roughly 1000 times more quasars per comoving volume of space of the same intrinsic luminosity (i.e. luminosity of quasar measured at the source rather than apparent luminosity when measured at earth) at z=2.5 than there are at z=0.5. See figure 3 in Fan’s paper.

From Fan’s paper Evolution of High-Redshift quasars.

http://sait.oat.ts.astro.it/MSAIt770206/PDF/2006MmSAI..77..635F.pdf

P.S.
I believe the closest quasar is 600 million light years from earth, in the Cygnus A (3C405) galaxy.

http://laserstars.org/news/3C405.html

Cougar
2007-Sep-29, 03:23 AM
Does the cloud gas density increase or does the density of the number of gas clouds increase?
At very early times, the entire universe was a "cloud" of hydrogen and helium gas.


How does one answer this question observationally?
A good question. Quasars are not used to test time dilation. Their major use in astronomical research is through the detection of their spectral absorption lines, which show what gases the very distant quasar light has gone through on its long journey to our neighborhood, and at what distances those gas clouds are. Because of their tremendous luminosities and distances, quasars are our deepest probes of the makeup of the universe. Observationally.

William
2007-Sep-29, 06:06 AM
In reply to Cougar’s comment #13, on time dilation.

1) Two papers by Hawkins were referenced that show Quasars do not exhibit time dilation with redshift.

2) In addition a review quasar paper was referenced by Fan that states the well known observation that quasars do not exhibit evolution in metallicity, from redshift of about 0.5 to 3.0. (i.e. Quasars at z=0.5 have the same spectrum as quasars up to about z=3.)

The two findings, that quasars do not exhibit time dilation with redshift and that quasar spectrum does not exhibit a change in metallicity (from z=0.5 to 3) are mutually supportive. There appears to be no papers which refute these findings. (i.e. Hawkins’ observations and analysis appears to be valid and Fan’s finding is not controversial.)

There seems to be evidence of a paradox. These observations cannot be explained by the standard theory and there are no papers refuting either the observations or the analysis. Some thing is possibly incorrect with the standard theory/model of quasars.

In addition Fan in his paper noted that there appears to be some mechanism that limits the quasar “black hole” to a maximum mass of less than 10^10 solar masses. This statement is consistent, I believe with the findings other researchers.

Does anyone have any logical arguments to refute the above statements?

StupendousMan
2007-Sep-29, 12:51 PM
There seems to be evidence of a paradox. These observations cannot be explained by the standard theory and there are no papers refuting either the observations or the analysis. Some thing is possibly incorrect with the standard theory/model of quasars.


Fair enough.

Now, if you can come up with a better model for quasars than "big black hole at center of galaxy, surrounded by an accretion disk", please do. Make sure that your model is consistent with the wealth of observational data on quasars and AGN in the local universe, as well as at high redshift.

Until you come up with a better model -- which explains more of the data than the current model -- I'll continue to use the current model. So will most of the astronomical community. That's the way scientists work: we devise a model which is consistent with observations, adheres to theory, and is as simple as possible.

Nereid
2007-Sep-29, 02:38 PM
In reply to Cougar’s comment #13, on time dilation.

1) Two papers by Hawkins were referenced that show Quasars do not exhibit time dilation with redshift.

2) In addition a review quasar paper was referenced by Fan that states the well known observation that quasars do not exhibit evolution in metallicity, from redshift of about 0.5 to 3.0. (i.e. Quasars at z=0.5 have the same spectrum as quasars up to about z=3.)

The two findings, that quasars do not exhibit time dilation with redshift and that quasar spectrum does not exhibit a change in metallicity (from z=0.5 to 3) are mutually supportive. There appears to be no papers which refute these findings. (i.e. Hawkins’ observations and analysis appears to be valid and Fan’s finding is not controversial.)

There seems to be evidence of a paradox. These observations cannot be explained by the standard theory and there are no papers refuting either the observations or the analysis. Some thing is possibly incorrect with the standard theory/model of quasars.

In addition Fan in his paper noted that there appears to be some mechanism that limits the quasar “black hole” to a maximum mass of less than 10^10 solar masses. This statement is consistent, I believe with the findings other researchers.

Does anyone have any logical arguments to refute the above statements?Yes, it is very easy to show that the above contains several, rather elementary, errors.

Let's start here: "The two findings [...] are mutually supportive." This is an assertion, made without any support. In the post, which I quote in full above, you have not even tried (it seems) to link metallicity with time dilation, either specifically wrt quasars or in general.

Next: "There seems to be evidence of a paradox. These observations cannot be explained by the standard theory" An earlier post, by Nereid, pointed out that the 2007 Hawkins paper does exactly what you claim it can't (explain the observations by the standard theory). True, this is not an error in your logic; however, it is a rather powerful refutation of your thesis, don't you think?

Finally: "Does anyone have any logical arguments to refute the above statements?" Your post is a number of poorly connected/related statements, dealing with observations, papers, analyses, and the (unified) model of quasars (and AGN). As such, no single refutation is possible.

More generally, as StupendousMan has pointed out, perhaps the biggest problem with your post is its apparent deep misunderstanding of the nature of (astronomical) science.

William
2007-Sep-29, 04:10 PM
In reply to StupendousMan’s first comment:

The point of this thread was to provide sufficient evidence to justify the statement that there appears to be a paradox, in which the standard astrophysical model of quasars cannot explain observations. The evidence and analysis that supports this statement (see above comments for details) has not been refuted by the scientific community and there has been sufficient time for the scientific community to response.

It is asserted that StupendousMan is an intelligent, informed, sceptic. The following it is believed is StupendousMan’s acceptance of the above statement based on the evidence and logic presented in the forum.


Fair enough.


In reply to StupendousMan’s second comments & general position:


Now, if xxx can come up with a better model for quasars than "big black hole at center of galaxy, surrounded by an accretion disk", ... Make sure that … model is consistent with the wealth of observational data on quasars and AGN in the local universe, as well as at high redshift.

Until xxx come(s) up with a better model -- which explains more of the data than the current model – xxx (will) continue to use the current model. ….That's the way scientists work: (they) devise a model which is consistent with observations, adheres to theory, and is as simple as possible.


StupendousMan, I support the generalized form of your comment with the exception of the statement that “the solution must be as simple as possible and must adhere to theory”.

I believe the scientific community's objective is to solve the problem, to find the truth. The selection of models and theories is not an ascetic, subjective process. This is not Aristotle or theoretical science where the theory/model is disconnected from reality. If theory does not explain the observations other hypotheses are considered and after some work the standard theory will likely change or be replaced by a more advanced model. This is not an infinite process. In the case of other fields of science, the theories/models start to match reality and there is no longer a need to introduce new hypotheses.

For example in the field of geophysics the data that supported the tectonic plate movement theory was ignored and those presenting it were ostracized, up until the mid 1970s. Tectonic plate movement is now considered to be a fact not a theory and has revolutionized the field of geophysics.

Back to quasars.

There are a number of recent solid astrophysics papers that provide data and analysis to attempt to address the quasar paradox. The ideas and hypotheses in the papers are the author’s not mine.

StupendousMan
2007-Sep-29, 05:35 PM
There are a number of recent solid astrophysics papers that provide data and analysis to attempt to address the quasar paradox. The ideas and hypotheses in the papers are the author’s not mine.

Great! Then we'll have to wait for the author to describe them, since you seem unable to do so. In the meantime, we'll go back to work with our current models.

William
2007-Sep-29, 06:31 PM
In response Nereid's comment:

I am not sure I understand your point or your concern. I provided a quote from Hawkins' paper 2007 that states that Hawkins believes his 2007 data and analysis supports the data and analysis from his 2001 paper that quasars do not exhibit time dilation.

Do you have a paper that refutes Hawkins' 2001 or 2007 paper?

I noted what the author of both papers said about his observations and his analysis. How can you and why would you object to that comment?

Yes, I understand that Hawkins' findings challenges the standard model for quasars. That is the definition of a paradox.

The following is the quote from Hawkin's 2007 paper which notes his findings reinforces the result of Hawkins (2001).

But, please let's agree to disagree. I am not trying to change your viewpoint. I am interested in scientific discussion concerning new scientific papers about an interesting scientific subject not simple argument or contradiction.


After the first primitive estimates of timescale discussed in the Introduction, and when the Fourier power spectrum was plotted in the form of a log/log plot, it was clear that there was no obvious break in a linear relation. This situation persisted as more data was added, and it was in this context that the short term MACHO data was added as the only realistic way of extending the baseline. It is quite remarkable that for the case of the observer’s reference frame the straight line relationship was maintained, covering three orders of magnitude in time and reinforcing the result of Hawkins (2001).

William
2007-Sep-29, 06:44 PM
In reply to StupendousMan comment:


Great! Then we'll have to wait for the author to describe them, since you seem unable to do so.

I think it would be great if we could raise the level of discussion in this forum so we could invite authors to comment and answer respectful, thoughtful questions concerning their papers.

StupendousMan, a thoughtful sceptic is an important component of scientific discussion. I respect your comments. I have read through the papers I mentioned and will present them in another thread, at a later date.

Nereid
2007-Sep-29, 11:59 PM
In response Nereid's comment:

I am not sure I understand your point or your concern. I provided a quote from Hawkins' paper 2007 that states that Hawkins believes his 2007 data and analysis supports the data and analysis from his 2001 paper that quasars do not exhibit time dilation.

Do you have a paper that refutes Hawkins' 2001 or 2007 paper?

I noted what the author of both papers said about his observations and his analysis. How can you and why would you object to that comment?

Yes, I understand that Hawkins' findings challenges the standard model for quasars. That is the definition of a paradox.

The following is the quote from Hawkin's 2007 paper which notes his findings reinforces the result of Hawkins (2001).

But, please let's agree to disagree. I am not trying to change your viewpoint. I am interested in scientific discussion concerning new scientific papers about an interesting scientific subject not simple argument or contradiction.William, I had a whole post full of points and concerns (not just one of each).

I began where the post (of yours) I quoted finished ("Does anyone have any logical arguments to refute the above statements?"). To summarise in a single sentence: your so-called summary contains flawed logic, faulty understanding of astronomy as a science, (by now) outrageous mis-characterisations (of Hawkins' papers), and more.

I will say this once again: the 2007 Hawkins paper is explicit: it explains the observations by the standard theory.

Having got this far, it seems clear (to me, anyway) that you are presenting an ATM idea (to the effect that observations interpreted as showing quasar variability {insert qualifier concerning domain here} must be at least paradoxical wrt 'the standard theory').

In an earlier post I asked if you would be interested to explore the 2007 Hawkins paper in more detail, to see how, in more detail, the observations are, in fact, consistent with the standard theory. I note, for the record, that you chose to not answer.

To try to tackle one serious flaw in the logic of your posts: the link between 'It is quite remarkable that for the case of the observer’s reference frame the straight line relationship was maintained, covering three orders of magnitude in time and reinforcing the result of Hawkins (2001)' and 'There seems to be evidence of a paradox. These [Hawkins] observations cannot be explained by the standard theory' is, in your posts, never made explicit (as far as I can see).

Perhaps you assume that the standard theory of quasars cannot account for 3 OOM of quasar variability seeming to show no time dilation?

Perhaps you simply do not understand the standard theory of quasars sufficiently well to appreciate how it can, in fact, be consistent with these 3 OOM of quasar variability?

Perhaps ...

In any case, unless and until you make explicit the link you seem to be making between what you understand to be the standard theory and what you understand to be the observations, I don't know how much further I can go to disabuse you of your (apparent) misunderstanding.

In closing, may I also point out that I have looked at only your 'Hawkins' assertions; based solely on your apparent, deep, misunderstanding here, I infer that you may have similarly, deeply, misunderstood the relevant quasar metallicity papers.

Spaceman Spiff
2007-Sep-30, 02:33 AM
In a nutshell, William, I think that what Stupendous Man is "griping about" is that you came to this forum (called "Questions and Answers", ahem) having already formed many of your own conclusions about what is and is not understood about quasars - even before finding out what the current state of knowledge is by reading the literature. What's more, many of these conclusions are quite misinformed.

May I suggest that if you've a specific question about what is known or not known about quasars, then make it. Otherwise, you are welcome to take your conjectures (etc) to the ATM forum.

William
2007-Sep-30, 05:16 PM
In reply to Spaceman Spiff:

The questions listed above were taken directly from recent published papers on quasars. I have found presentations from recent quasar astrophysics conferences that ask the same questions and that refer to Fan's paper.

What is your objection or the objection of others? Professional astrophysicists are asking these questions. Is it incorrect to ask the same questions, in the question and answer section of an astronomy forum?

Do you have a paper that refutes the observations, analysis, or author's comments? Do you have a paper that provides an answer to these questions?

For example the following is an excerpt Hawkins' 2001 paper. I noted that Hawkins in his 2007 stated that the results published in his 2007 reinforced the findings of his 2001 paper. i.e. That it is still a valid problem.

http://arxiv.org/pdf/astro-ph/0105073

"Time Dilation and Quasar Variability" by M. R. S. Hawkins University of Edinburgh, Royal Observatory.


ABSTRACT
The timescale of quasar variability is widely expected to show the effects of time dilation. In this paper we analyse the Fourier power spectra of a large sample of quasar light curves to look for such an effect. We find that the timescale of quasar variation does not increase with redshift as required by time dilation. Possible explanations of this result all conflict with widely held consensus in the scientific community.

The lack of quasar evolution with redshift Z= 0.5 to 3.0, is another problem.

From Fan's paper:

http://www.physics.uci.edu/Cosmology/Fan_Xiaohui.pdf



The last few years has witnessed the discovery of luminous quasars at z > 6, which are likely anchored by supermassive black holes with > 10^9 M_. Furthermore, the spectral energy distribution of these quasars, across the entire electromagnetic spectrum, shows very little evolution from their low-redshift counterparts. Is the existence of luminous quasars, with massive black holes and “mature” SEDs and high metallicity a big surprise? Or this is something totally expected?

and


– In sharp contrast to the strong density evolution is the lack of strong evolution of quasar spectral properties. The strength Fan: High-redshift Quasars 637 of emission lines remains roughly constant through cosmic history.

and from again from Fan's quasar paper.


One intriguing feature that we noticed is the apparent lack of quasars with BH masses larger than a few times 10^10 solar masses, at all redshift.


From Mirabel's paper that discusses the evolution of Black Holes which is important as the BH's are the engines that drive the quasars. (Also related to Fan's question on black hole evolution. Fan notes in his paper that it is almost not possible to have formed BH of sufficient size for high redshift quasars, at that time in the early universe.)


"Microquasars: Progress and Open Questions" by I.Mirabel

http://arxiv.org/pdf/astro-ph/0701837


2) If black holes of intermediate mass (≥ 100 M) are prolific, why has no one been identified in the Milky Way or the Magellanic Clouds, where the dynamical mass of compact objects in binaries can be determined ?

antoniseb
2007-Oct-01, 01:02 AM
I've closed this thread. William would have been well served to have acknowledged input from other members, and not stubbornly promoted an ATM idea in the mainstream section.