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trinitree88
2009-Oct-23, 06:38 PM
The authors discuss issues involving :
1.the lack of nearby QSO's, an evolutionary explanation that eludes us.
2. the inconsistencies between the absorbtion lines, when measuring tangentially and along the QSO line of sight.
3. the redshift correlations between QSO's and their host galaxies.

They note that the prevailing view is correct in:
1.the association of QSO's with their host galaxies shows that the objects are much brighter than the rest of the galaxy and their hosts have decreasing angular sizes with increasing redshift...
2. the absorption lines in many cases have a successful interpretation in terms of intervening galaxies or gas along lines of sight...
3. in cases involving gravitational lensing, the QSO's have much higher redshifts than the lensing galaxies.

SEE:http://arxiv.org/PS_cache/arxiv/pdf/0910/0910.4297v1.pdf

Cougar
2009-Oct-23, 07:56 PM
SEE:http://arxiv.org/PS_cache/arxiv/pdf/0910/0910.4297v1.pdf

Here, Lopez-Corredoira discusses the very high luminosity at high redshift "problem."



The anisotropy of the QSO radiation, observable only when the beam is pointed towards us, would also reduce the luminosity; but the number of sources would be much higher, a huge number, and we would then see a large number of them in the nearby Universe...

I don't follow why beaming implies that the number of sources would be "a huge number," with many nearby.

Kwalish Kid
2009-Oct-23, 08:10 PM
They note that the prevailing view is correct in:
3. in cases involving gravitational lensing, the QSO's have much higher redshifts than the lensing galaxies.
I can see why one would want to isolate this point in order to make it seem like there was a stronger case for some kind of intrinsic redshift hypothesis.

It pretty much is the case that the only way to distinguish a QSO at a different redshift from a galaxy that it visually coincides with is through gravitational lensing. But that does not change the fact that every time we have ben able to distinguish the distances between such QSOs and visual-host galaxies, we get distances appropriate for their redshifts. This really blows the intrinsic redshift hypotheses out of the water.

parejkoj
2009-Oct-23, 08:50 PM
Wow... Lopez-Corredoira really doesn't know what he's talking about.

Throughout the paper he uses the terms AGN and quasar interchangeably, but he's often talking about quite different objects (by luminosity, anyway). Low luminosity AGN and high luminosity AGN, such as quasars, would probably have different environments, evolution and host galaxies. And, in fact, the data seems to show this.

Also, it's rather amusing that he cites Narlikar repeatedly when talking about the black hole model, but makes no mention of Urry & Padovani, or J. Shields, although he does cite Antonucci... once. In fact, his choice of citations is rather odd in general, but seem my last point for the probably explanation for this.

If he's going to complain about a lack of luminous AGN at low redshift, he needs to explain what he means by "luminous" and "low." If you look at the over-all density of AGN (by luminosity), there should be roughly 1 AGN with an X-ray luminosity above 1044 erg/s below z~0.05. And we've probably found it (http://adsabs.harvard.edu/abs/2009MNRAS.399..129L).


Using the expression for Eddington’s luminosity, based on the characteristic scale of the Schwarzshild radius of a black hole, gives luminosities of the order of 1044 erg/s (Kembhavi & Narlikar 1999, §15.3)

Uhh... that's dependent on black hole mass, and "Eddington's luminosity" is more of a reference point, not a hard limit.

The citation of Jain & Dev (2006) (http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:astro-ph/0509212), although an interesting paper, suggests to me that the quasar age estimation was not using an appropriate model.


In view of these evidences, orthodox cosmologists claim now that the star formation began very early and produced metals up to the solar abundance quickly, in roughly half Gyr. However, it is not enough to come up with such a surprising claim, it needs to be demonstrated, and I do not see any evidence in favor of such a quick evolution in the local galaxies.

Why would star formation in local galaxies be the same as star formation in distant galaxies? We already know that star formation rates peaked around a redshift of 2-3, which is similar to the peak of quasar activity.

And that leads directly into section 5, "Evolution or non-evolution of QSOs." He's apparently missed out on the past 10-15 or so years of astrophysics related to cosmic downsizing (once termed "luminosity dependent density evolution").

His section 6, "Triggering of Activity" is probably the one with the most actual uncertainty in current research. Mergers probably do trigger AGN, but the timescale on which the AGN is visible and the timescale on which the merger is (easily) visible are probably quite different.

"Periodicity of redshifts" has been thoroughly shot down. People who continue to publish on it just don't understand the meaning of the term "selection function."

As to section 9: if he wants to use the standard picture that low luminosity AGN and quasars are just different points along a continuum of objects, as suggested by his use of the terminology, then he can't use purported observations of non-cosmological redshifts for quasars, but cosmological redshifts for lower luminosity AGN. Also, he makes absolutely no mention of observations (commonplace, these days) of host galaxy spectra with the same redshift as the quasar.

His complaints about the unification model in section 10 are complaints about details of the models. It's rather like the "punctuated equilibrium" vs. "gradualism" debate in biology: obviously, since biologists can't agree on which one is correct, creationism must be right! :rolleyes:

Which leads me to my final point: the paper is put forward as if there were some substantial debate among AGN researchers. There isn't. He's trying very hard to put forward a fringe view as if it were on similar footing to the mainstream view. It's not. Are a few of his points valid criticisms of modern AGN theory? Yes. But you'll never get an astronomer who studies AGN (and there are at least three on this board) to claim that we know everything about them. But that doesn't mean they aren't powered by black holes...

parejkoj
2009-Oct-23, 08:57 PM
Here, Lopez-Corredoira discusses the very high luminosity at high redshift "problem."



The anisotropy of the QSO radiation, observable only when the beam is pointed towards us, would also reduce the luminosity; but the number of sources would be much higher, a huge number, and we would then see a large number of them in the nearby Universe...

I don't follow why beaming implies that the number of sources would be "a huge number," with many nearby.

He actually got that correct: if the radiation is highly beamed, then we'd expect there to be a large number (you can compute how large based on the density of observed objects and the estimated beaming angle) because for every object with it's beam pointed toward us, there'd be many more with the beam pointed elsewhere.

Of course, that's exactly what we find when we talk about actual beamed AGN, such as blazars. They make up a very small fraction of the total AGN population, but what we see in their emission suggests we're looking right down the throat of the monster. Accretion onto a supermassive black hole has no problem accounting for the observed energies of AGN without including beaming, even up to luminosities of ~1046 erg/s.

trinitree88
2009-Oct-24, 03:15 PM
Thanks for the discussions guys. This is an area I'm curious about but hardly versed in, so I keep my personal comments to a minimum, and I learned a few things here. pete