Quasar Time Dilation

[CraigS]

Hi All;

In spite of the (considerable) risk of starting another skirmish, I've decided to forge ahead and ask whether anyone has heard/read any follow-ups on Mike Hawkins' article in April's Monthly Notices of the Royal Ast. Society on 'Time Dilation in Quasar Light Curves':

http://www3.interscience.wiley.com/j...45710/abstract

or the journo's article:
http://www.physorg.com/news190027752.html

Whilst this came up in the other thread on Galaxies & Inflation, (by one of the Alex es - Jarva), I've been left hanging ever since I read the article.

Please note I'm only asking if anyone has heard of any follow-ups - I reckon there's some really interesting stuff which might come out of Hawkins' continued investigation ... (one way or the other).

He started it .. so it'll be great to see him finish it !



Cheers

[renormalised (Carl)]

No....I'll have to keep an eye out for any.

Ah....like your avatar A Calabi-Yau manifold

Just like the universe itself, we're all multidimensional beings (well, most of us anyway)

BTW..I'll send you a copy of the full article, if you want to read it

[Kal (Andrew)]

I read the journo article but I don't understand how they can come to the conclusion that "even though the distant quasars were more strongly redshifted than the closer quasars, there was no difference in the time it took the light to reach Earth."

Any cliff notes if you have read the article?

[renormalised (Carl)]

You have to read the actual paper, Kal. If you want it, I can post it to you. It's too large to attach here.

I haven't read this article yet, however what he's saying is that depsite the redshift showing that "X" quasars are further away than "Y" quasars, there is no apparent slowing down of the light due to time dilation caused by expansion. Now, that means this...either expansions is wrong, redshift is wrong, or if they're both correct then there must be some other mechanism causing this apparent anomaly. It could also be that his sample size is too small and he hasn't taken into account enough observations on a large enough set of quasars (a possibility), or he has misinterpreted what he has seen (possibly), or he hasn't fully looked at the power spectrum of the quasars across all wavelengths and fully considered the environment from which this light is emanating from. Most of these surveys are done in the vis-UV end of the spectrum. That means at most quasar's distances that light would've been originally in the hard x-ray and gamma ray region of the spectrum when it was emitted. That means a whole new set of circumstances has to be taken into consideration when dealing with its origins.

[CraigS]

Ok .. so now I've read the complete paper, I'm even more interested.

... so here comes the controversy ... oh no !! )



"There is however surprisingly little direct evidence that the Universe is expanding. As mentioned in Section 1, searches for time dilation in gamma-ray bursts do not provide a conclusive test. Supernova light curves on the other hand appear to show convincing evidence of time dilation (Foley et al. 2005), which would rule out a non-expanding universe as an explanation for the results presented here for quasar light curves. Although this result has been challenged in an interesting paper by Crawford (2009) on the basis of bias in the sampling procedure, it seems fair to say that the result is still generally accepted."

So,
GRBs => not a conclusive test for universe expansion,
Supernova light curves => convincing evidence of expanding universe (with an outstanding challenge);
Quasar light curves => no dilation but not evidence for a static universe.

So that's a pretty up-to-date summary of where things stand at the moment.

Fascinating !

Cheers

[renormalised (Carl)]

Originally Posted by CraigS

Ok .. so now I've read the complete paper, I'm even more interested.

... so here comes the controversy ... oh no !! )



"There is however surprisingly little direct evidence that the Universe is expanding. As mentioned in Section 1, searches for time dilation in gamma-ray bursts do not provide a conclusive test. Supernova light curves on the other hand appear to show convincing evidence of time dilation (Foley et al. 2005), which would rule out a non-expanding universe as an explanation for the results presented here for quasar light curves. Although this result has been challenged in an interesting paper by Crawford (2009) on the basis of bias in the sampling procedure, it seems fair to say that the result is still generally accepted."

So,
GRBs => not a conclusive test for universe expansion,
Supernova light curves => convincing evidence of expanding universe (with an outstanding challenge);
Quasar light curves => no dilation but not evidence for a static universe.

So that's a pretty up-to-date summary of where things stand at the moment.

Fascinating !

Cheers

Pretty much. What most people don't know is that there's more than one BB model. At the last count I think it was somewhere up around 10-20 different models...some more plausible than others, but all pointing to the same conclusion...expansion.

There are problems with all observations, including those of the quasars, as I mentioned in my last post. Even the fact that they've compared the closer quasars to those that are at large values of z is in itself problematical. Simply because the closer quasars are less luminous for good reason....they're a lot older and have different characteristics of accretion and emission than the younger quasars. It's like comparing a 10 year old kid with his/her grandparents. Whilst the basics maybe very similar, it's the details which actually matter. You'll find this out as you read more about the subject

[sjastro]

There are problems with all observations, including those of the quasars, as I mentioned in my last post. Even the fact that they've compared the closer quasars to those that are at large values of z is in itself problematical. Simply because the closer quasars are less luminous for good reason....they're a lot older and have different characteristics of accretion and emission than the younger quasars. It's like comparing a 10 year old kid with his/her grandparents. Whilst the basics maybe very similar, it's the details which actually matter. You'll find this out as you read more about the subject

It's also why galaxy data is much more reliable for supporting an expanding Universe. Apart from the much larger sample size, Type IA supernovae light curves are independent of the host galaxy's z-value.

The age of the galaxy doen't complicate the picture as does Quasars.

Steven

[renormalised (Carl)]

Precisely, and that outstanding challenge to Type IA light curves is mostly due to the actual mechanism of the explosion. There are some anomalous results from Type IA light curves which may point to slightly different mechanisms occurring in some cases. However, that in no way invalidates most of the results as they show clear evidence of being the nuclear detonation of white dwarfs.

[CraigS]

Originally Posted by renormalised

There are problems with all observations, including those of the quasars, as I mentioned in my last post. Even the fact that they've compared the closer quasars to those that are at large values of z is in itself problematical. Simply because the closer quasars are less luminous for good reason....they're a lot older and have different characteristics of accretion and emission than the younger quasars. It's like comparing a 10 year old kid with his/her grandparents. Whilst the basics maybe very similar, it's the details which actually matter. You'll find this out as you read more about the subject

If I'm reading the paper correctly, I think they're saying that they've corrected for the correlation between redshift and time-scale (which I think follows on from the redshift and luminosity correlation). They did this by limiting the absolute magnitude range to exclude the correlation (ie: a reduced dataset). They also seem to have done a bunch of other corrections/checks to eliminate other known correlations.

Looks like a pretty thorough analysis (& why wouldn't it be .. pretty reputable source, I would think).

[CraigS]

Originally Posted by sjastro

It's also why galaxy data is much more reliable for supporting an expanding Universe. Apart from the much larger sample size, Type IA supernovae light curves are independent of the host galaxy's z-value.

The age of the galaxy doen't complicate the picture as does Quasars.

Steven

G'Day Steven;

Yep.

I think they go on to make the point that something has to give to explain why the quasar data doesn't show the time dilation, none-the-less.

Cheers

[renormalised (Carl)]

Originally Posted by CraigS

If I'm reading the paper correctly, I think they're saying that they've corrected for the correlation between redshift and time-scale (which I think follows on from the redshift and luminosity correlation). They did this by limiting the absolute magnitude range to exclude the correlation (ie: a reduced dataset). They also seem to have done a bunch of other corrections/checks to eliminate other known correlations.

Looks like a pretty thorough analysis (& why wouldn't it be .. pretty reputable source, I would think).

I'll actually have to read the paper myself before I comment on the specifics, but the fact that they have such a reduced dataset and have essentially ignored the correlations is an important point to bring up here.

These correlations are important in determining just what type of mechanism is controlling the emissions from the quasars and how it related to quasar age, distance etc. Without those correlations, you can't really make head nor tail of what is occurring, all you can do is speculate on how luminosity and redshift are related and what mechanism is possibly driving the luminosity and variability in the quasars. That's why you need to read the other papers that he cites from, including those earlier one of his own. You can only draw some basic conclusions from this paper, but only about this paper. Whilst many of the other studies have been done with even fewer quasars and quite a few others have been done with a lot more, arbitrarily excluding the correlation (or anti-correlation data as the case may be) data is not sound. He may have done a thorough analysis, but you have to look at it in the light of other results. It will be good to see what others make of his results and to see what they decide to publish.

[CraigS]

Originally Posted by renormalised

I'll actually have to read the paper myself before I comment on the specifics, but the fact that they have such a reduced dataset and have essentially ignored the correlations is an important point to bring up here.

These correlations are important in determining just what type of mechanism is controlling the emissions from the quasars and how it related to quasar age, distance etc. Without those correlations, you can't really make head nor tail of what is occurring, all you can do is speculate on how luminosity and redshift are related and what mechanism is possibly driving the luminosity and variability in the quasars. That's why you need to read the other papers that he cites from, including those earlier one of his own. You can only draw some basic conclusions from this paper, but only about this paper. Whilst many of the other studies have been done with even fewer quasars and quite a few others have been done with a lot more, arbitrarily excluding the correlation (or anti-correlation data as the case may be) data is not sound. He may have done a thorough analysis, but you have to look at it in the light of other results. It will be good to see what others make of his results and to see what they decide to publish.

Yep. Agreed.
Cheers

[renormalised (Carl)]

Do you have access to or use on your own computer any bibliography software??. If you have, I have BibText files of resources you can use to find articles,

[sjastro]

Interesting paper.

Fourier Analysis can be a minefield by filtering out good data but the methodology looks OK.

Comparing the paper to the time dilation of Type IA supernovae in galaxies, there are fewer variables to contend with in the supernova data.
http://users.westconnect.com.au/~sja...n_redshift.pdf

In this case "all" that has to be done is calculate the light curve of the supernova in the galaxy's (supernova) rest frame.

This is done using the SNID algorithm.
The authors of the algorithm go to great pains in defining SNID.

"What does SNID stand for?

Supernova Identification. It does not stand for any of the following:

Scandinavian Network for Infectious Diseases
Smart Network Interface Device
Studies in National and International Development
Subscriber Network Interface Device
Sud Nivernais Imphy Decize"

Steven

[renormalised (Carl)]

There's quite a few papers on SnIA and cosmology on the net, mentions a few different pieces of software for Sn identification.

[CraigS]

So having skimmed thru six of this guy's papers (Hawkins), I think he's got the analysis side fairly well sorted.

He looks like he's spent about 12 years on it so far !!

His focus seems to be on the search for the nature Darkness (Energy, Matter), rather than what makes a quasar tick.

A candidate for the 'Prince of Darkness' title, huh ?

Love to know what his peers think ie: what/where is their feedback ?

Cheers

[renormalised (Carl)]

"Prince of Darkness"....I'm sure he would be thrilled being called that

Best way to see how well his colleagues and peers think of him is to see how often he's cited in the relevant literature. And the level of those citations...i.e. importance.

[sjastro]

Originally Posted by CraigS

Love to know what his peers think ie: what/where is their feedback ?

Cheers

You can ask directly!

You can contact Ned Wright.
Despite the negative remarks made by one particular individual, Ned is one of the very few cosmologists who converses directly with the public.

http://www.astro.ucla.edu/~wright/b4u-write.html

http://en.wikipedia.org/wiki/Edward_L._Wright

Regards

Steven

[renormalised (Carl)]

Ned's tutes should be required reading for anyone wanting to go off at tangents with wild ideas. Then after reading and (hopefully) understanding what he has written, if they still want to go off on tangents, at least then they'll know enough to not make a complete fool of themselves.

[CraigS]

Originally Posted by sjastro

You can ask directly!

You can contact Ned Wright.
Despite the negative remarks made by one particular individual, Ned is one of the very few cosmologists who converses directly with the public.

http://www.astro.ucla.edu/~wright/b4u-write.html

http://en.wikipedia.org/wiki/Edward_L._Wright

Regards

Steven

Hmmm;

Thanks for that.
I'll have a read thru his FAQs when I get a chance. They look interesting.
I think I'll be bouncing my real questions around here first, though.

Fortuitously, I'm also reading a book called "Einstein's Telescope" by Evalyn Gates, so I'm getting an infusion of grav. lensing and the hunt for dark stuff from there. Its reasonably up to date, which helps. Mind you, I reckon I'll have to read it about half a dozen times before it sinks in. (Its a bit easier going than the Prince of Darkness's papers, though ...)



Cheers.