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Author | Topic: Tired Light | |||||||||||||||||||||||||
Percy Member Posts: 22498 From: New Hampshire Joined: Member Rating: 4.9 |
Here's one of the spectra Eta is referring to from page 1235 of the paper at AJ Vol 121 pg 1232. The Lyman beta line is the little bump on the far left around 5200 angstroms:
Don't both clicking on "Click to enlarge", it's already as big as it's going to get. --Percy
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Eta_Carinae Member (Idle past 4402 days) Posts: 547 From: US Joined: |
that is correct.
At high redshift people don't realise the difficulty of getting the data. You need long integration times and thus you aren't going to get the resolution like the SS Cygni spectrum you provided earlier. But these spectra are still pretty good. The problem with the Balmer series lines H alpha, H beta and so on is that at these high redshifts they have been redshifted into wavelengths we cannot observe on the ground due to the water vapour in the atmosphere making it opaque at these wavelengths. Thus the Lyman lines are used since those UV lines (at rest wavelengths) are shifted into the red part of the visible as these spectra show. Another factor going on is if you notice to the left of the big Lyman Alpha line there is a huge dropoff of the continuum level - the Lyman trough. This is why the Lyman Beta line is much weaker and sometimes seems almost buried in the noise. This is because of the absorption by hydrogen along the path from the quasar to us. In nearby AGN this feature isn't there. With the new Spitzer telescope being a space observatory you are starting to see spectra in the IR of these ojects. One link I provided showed a mid-far IR spectra with some of the Paschen series of Hydrogen. What peaceharris is doing is basically being guilty of not knowing how spectra are interpreted and why the Balmer lines are not usually plotted and why the intervening absorption dampens the Lyman Beta line and also, as can be seen, makes the stron Lyman Alpha line asymmetric.
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Admin Director Posts: 13036 From: EvC Forum Joined: Member Rating: 2.1 |
Eta in Message 284 and Message 285:
Are you blind?...You haven't a clue!!!!!! While it seems like there should be some emotional satisfaction gained for patiently explaining science to an arrogant and frustrating know-nothing, such as by treating him in a denigrating manner, I'm trying to discourage this. If you cover all the bases on the science side, whether he is blind or hasn't a clue will emerge from the discussion and require no explicit statement. Like I said earlier, EvC Forum is a science site, and the tradition here at EvC Forum is to place the heaviest burden on those most familiar with science. I apologize for inconsistently and unevenly pushing this point, but if you've actually contributed to 150 peer reviewed publications then the standards you should be held to are god-like.
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Percy Member Posts: 22498 From: New Hampshire Joined: Member Rating: 4.9 |
Thanks for all this information. An aside, and this will probably fall into your "How could he not know that" category, but one of the things I learned while trying to figure out what you were saying about spectra is that the absorption spectrum of intervening hydrogen clouds is a function of their red shift. It's obvious, I know, but I had never even thought about it before.
--Percy
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Eta_Carinae Member (Idle past 4402 days) Posts: 547 From: US Joined: |
I think the 'are you blind' comment is appropriate. No one who is being honest can say they cannot see the Lyman Beta peak in those spectra.
'you haven't a clue' I think seems obvious. I only make comments like that when I feel I'm being lied to. peaceharris is I think actually lying when he says he cannot see the Ly Beta line. People being wrong is one thing - but the only posters I have ever got irritated at are peaceharris, lyndonashmore & buzsaw about 18 months ago. peace & lyndon I actually think in some posts are fibbing. buz was just inept.
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Eta_Carinae Member (Idle past 4402 days) Posts: 547 From: US Joined: |
Yes, in fact you can get the redshifts of the intervening clouds if they are dense enough. In fact you can work out their column densities.
Also from the immediate slope of the Ly Alpha line and the depth of the trough you can work out the size of the ionisation zone around the quasar and calculate how long it has been active. It's called the proximity effect. You can also estimate the wind velocity of the material being blown out of the quasar too.
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Admin Director Posts: 13036 From: EvC Forum Joined: Member Rating: 2.1 |
I concede that there is a Pollyanna aspect to what I'm asking. It seems to require being blithely oblivious to what's really going on, and that does seem to be asking too much.
I know it seems like purposeful lying, but in most cases it isn't. The religious aren't the only ones capable of fooling themselves, remember N-Rays (Blondlot and N-rays - The Skeptic's Dictionary - Skepdic.com).
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Eta_Carinae Member (Idle past 4402 days) Posts: 547 From: US Joined: |
I somehow don't think that is what goes on here most of the time. I must admit I get sick to death of basically being called a conspiracist (the great evil atheist one) or a liar.
I'm not some 18 year old armed with Google and a vocabulary. I do this for a living because it's what I wanted to do from being 4 years of age - plus I have a talent for it which was spotted early in life. What possible reason would I have for lying about the data, falsifying theories and being an all around dope? All I ever want to do is to figure out how this universe ticks. I don't give a rats ass about t<0. peaceharris is an excellent example of a very little knowledge being a very dangerous thing - especially since I'm sure he has his conclusion already in place and he NEEDS the data to fit this.
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Admin Director Posts: 13036 From: EvC Forum Joined: Member Rating: 2.1 |
I was actually making a different point. I intended for you to apply my reference to Blondlot and N-Rays to PeaceHarris. I don't think Blondlot, a legitimately gifted scientist, was lying, and I don't think PeaceHarris, a considerably lesser light, is, either.
If you're old enough you might recall Tom Lehrer, a Harvard professor of mathematics who moonlighted in coffee houses singing songs of his own composition (Answers - The Most Trusted Place for Answering Life's Questions). He was once asked in an interview why he didn't do higher mathematics, and his reply was instructive. He said that above a certain point it just stopped making sense, and that he was only able to go so far. This is true for most of us about many things. The significance of principles beyond our grasp is as if they did not exist. Combine this with a preferred viewpoint and people can convince themselves of all kinds of things that aren't supported by the evidence. And combine this with certain personality traits that prevent ever conceding any error, such as Ashmore with his need to appear authoritative, and such as PeaceHarris with his need to appear privy to special insights, and you've got a deadly brew of ignorance. This is the den of iniquity you've entered by participating here, and as one of the privileged priests of science you're expected to move serenely among the lepers casting your pearls about without showing any signs of revulsion or distress.
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Adminnemooseus Administrator Posts: 3976 Joined: |
Say goodnight, tired topic.
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peaceharris Member (Idle past 5623 days) Posts: 128 Joined: |
I have marked the expected position for the Lyman alpha and Lyman beta lines in 2 of the spectra with Z>4 from AJ Vol 121 pg 1232.
In my opinion, for the spectrum with z=4.04, the Lyman beta line coincides with where the noise is at a local maximum, and for the spectrum with z=4.49, it coincides with where the noise is at a local minimum. This message has been edited by peaceharris, 04-12-2005 08:22 PM This message has been edited by Admin, 04-12-2005 08:39 PM
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NosyNed Member Posts: 9004 From: Canada Joined: |
In my opinion, for the spectrum with z=4.04, the Lyman beta line coincides with where the noise is at a local maximum, and for the spectrum with z=4.49, it coincides with where the noise is at a local minimum. As Eta pointed out, the determination of the lines out of the noise is not done by visual inspection. There are, apparently, mathematical techniques for doing this. In that light, your "opinion" is not worth one heck of a lot. Please run the math against this and show that the determinations done are in error.
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Eta_Carinae Member (Idle past 4402 days) Posts: 547 From: US Joined: |
Did you not read earlier where I mentioned that the lower wavelength side of the Lyman Alpha line is often heavily absorbed by intervening Lyman Alpha absorption? This is why the continuum drops by such a degree and you get the famous 'Lyman Alpha forest' where the other Lyman lines in the quasar would be located?
Did you miss that? The z=4.04 quasar has much less of this than the z=4.49 quasar. Notice how the continuum level is more depressed in the latter then the former. I would expect the Beta line to be difficult to pick out by eye in such a case. Also by placing a line you are also misleading yourself because the instrument response function is not that narrow. You really should take account of that and place a bar not a line. That is why you use the Lyman Alpha line & the Carbon, Nitrogen, Oxygen, Sulphur and Magnesium lines to the longer wavelength side for redshift determination. Redshift determinations in these examples are not done by matching one or two lines but many lines and the mathematical fitting of template spectra using some maximum likelihood analysis or even a neural net fitting. Tell me, WHY are you so desperate to believe that thousands of researchers for 40 years are incompetent in something this basic as spectral analysis? Why do you disregard the entire wealth of lines to the right of Lyman Alpha that ae used in this analysis? Why do the template spectra of nearby AGN match up so well with several dozen lines all in their correct places and the doublets in the correct ratios if this is 'just picking parameters' as you have put it? Why don't you study this further instead of picking holes before you have enough knowledge? I know for a fact you didn't know anything about the atmosphere not allowing much observation where the Balmer lines are and that you didn't think about the Lyman Alpha forest suppressing the continuum and the other lines.
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peaceharris Member (Idle past 5623 days) Posts: 128 Joined: |
NosyNed writes: As Eta pointed out, the determination of the lines out of the noise is not done by visual inspection. NosyNed,Eta has said on more than 1 occasion that the Lyman Beta line in those spectra can be determined through visual inspection. In message 284, Eta wrote, "At a z of 4 the Lyman Beta line is at 5125 Angstroms which is right at the edge of the plot for the 2 or 3 examples they have at zof about 4.You can see it rising up right at the edge or just in from the edge. Are you blind?" In message 290, Eta wrote, "No one who is being honest can say they cannot see the Lyman Beta peak in those spectra." and"peaceharris is I think actually lying when he says he cannot see the Ly Beta line. "
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Sylas Member (Idle past 5287 days) Posts: 766 From: Newcastle, Australia Joined: |
You can do a visual sanity check on the spectrum to see where the various lines are located; but for calculation of redshifts you don't rely on this kind of quick visual check. You do a more careful computed analysis.
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