# The quasar "in" NGC 7319

by Nereid
Tags: 7319, quasar
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[Moderator note: this thread has been created by splitting out posts related to 'the quasar "in" NGC 7319', in the quasar anomaly thread.]
 Quote by ratfink Hi RandallB, Try this
Ah, the quasar that shines through a 'hole' in a galaxy!

Those galaxies, they sure look 'solid', don't they? Who'd'a thunk that you could see right through one?

Of course, the breathless prose of a PR from a marketing department aside, it's interesting, but not at all unexpected.

Consider: Maffei 1 and Maffei 2; Dwingeloo 1; the Lockman hole; and Bill Keel's work (for example).
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 Quote by Nereid Ah, the quasar that shines through a 'hole' in a galaxy! Those galaxies, they sure look 'solid', don't they? Who'd'a thunk that you could see right through one? Of course, the breathless prose of a PR from a marketing department aside, it's interesting, but not at all unexpected. Consider: Maffei 1 and Maffei 2; Dwingeloo 1; the Lockman hole; and Bill Keel's work (for example).
Hi Nereid,
Thanks for the links, but there seems to be a problem. Whenever I click on them I get galaxies that have absolutely nothing to do with the one with the Quasar in the middle. I would be ever so grateful if you could check them and provide the real link that shows that the Burbridge galaxy has a hole in it with the quasar behind.
Thanks. I did find this one though
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 Quote by ratfink http://www.pickingjobs.com/job.php?jobid=38 Hi Nereid, Thanks for the links, but there seems to be a problem. Whenever I click on them I get galaxies that have absolutely nothing to do with the one with the Quasar in the middle. I would be ever so grateful if you could check them and provide the real link that shows that the Burbridge galaxy has a hole in it with the quasar behind. Thanks. I did find this one though
One step at a time, ratfink.

The first thing to establish is that the disks of spiral galaxies are not (uniformly) opaque. Here in our solar system, we are in such a disk, yet we can not only see out (all directions more than ~5o above the galactic plane, except for towards the bulge, and a few dusty regions), but right through the disk (even amateurs can take images of the Maffei group). Further, even wrt the ubiquitous hydrogen, there are 'holes' - the Lockman hole being one; if you check out the EUV Explorer, you'll find that it detected objects way, way beyond the local region of the Milky Way, despite the Lyman limit.

This shows that it is quite possible to see through the disk of a spiral galaxy, so that finding a quasar 'in' a spiral arm isn't verboten.

Next, if you read the Arp and Burbidge paper, you'll see that the QSO spectrum has absorption lines in it ... consistent with gas in the galaxy. Now this by itself doesn't rule out the QSO being 'in' the galaxy, it does rule it out of being 'in front of' the galaxy (and, BTW, AFAIK, no quasars along lines of sight through galaxies have been observed to have no such absorption lines).

So what's left, in terms of convincing observations supporting the interpretion that the QSO is 'in' the galaxy (and not far, far in the background)? Nothing; ergo, the QSO is where its redshift 'says' it is.

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## The quasar "in" NGC 7319

 Quote by Nereid One step at a time, ratfink. The first thing to establish is that the disks of spiral galaxies are not (uniformly) opaque. Here in our solar system, we are in such a disk, yet we can not only see out (all directions more than ~5o above the galactic plane, except for towards the bulge, and a few dusty regions), but right through the disk (even amateurs can take images of the Maffei group). Further, even wrt the ubiquitous hydrogen, there are 'holes' - the Lockman hole being one; if you check out the EUV Explorer, you'll find that it detected objects way, way beyond the local region of the Milky Way, despite the Lyman limit. This shows that it is quite possible to see through the disk of a spiral galaxy, so that finding a quasar 'in' a spiral arm isn't verboten.
Being possible is not the same as there being a hole in this particular galaxy. Has anyone repeated the work to see if Burbridge is correct?

 Next, if you read the Arp and Burbidge paper, you'll see that the QSO spectrum has absorption lines in it ... consistent with gas in the galaxy. Now this by itself doesn't rule out the QSO being 'in' the galaxy, it does rule it out of being 'in front of' the galaxy (and, BTW, AFAIK, no quasars along lines of sight through galaxies have been observed to have no such absorption lines).
Light from a quasar in a galaxy, next to the nucleus, passes through 50% of that galaxy. Hence we would expect it to have absorption lines characteristic of that galaxy. Has anyone checked to see if the absorption lines are typical of light passing through 100% of that galaxy or just 50% galaxy? (100% meaning the galaxy is behind the galaxy, 50% in the middle).

 So what's left, in terms of convincing observations supporting the interpretion that the QSO is 'in' the galaxy (and not far, far in the background)? Nothing; ergo, the QSO is where its redshift 'says' it is.
Not really. This quasar, if it is 'behind' the galaxy, must be in a prime spot for gravitational lensing. Ergo if it is 'behind' the galaxy then it should be lensed with a few images. If it is 'in' the galaxy then there will be no lensing and hence no images. How many images are there of this galaxy?
Answer: none! Ergo it is in the galaxy.
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 Quote by ratfink Being possible is not the same as there being a hole in this particular galaxy. Has anyone repeated the work to see if Burbridge is correct? Light from a quasar in a galaxy, next to the nucleus, passes through 50% of that galaxy. Hence we would expect it to have absorption lines characteristic of that galaxy. Has anyone checked to see if the absorption lines are typical of light passing through 100% of that galaxy or just 50% galaxy? (100% meaning the galaxy is behind the galaxy, 50% in the middle). Not really. This quasar, if it is 'behind' the galaxy, must be in a prime spot for gravitational lensing. Ergo if it is 'behind' the galaxy then it should be lensed with a few images. If it is 'in' the galaxy then there will be no lensing and hence no images. How many images are there of this galaxy? Answer: none! Ergo it is in the galaxy.
Ergo you have a profound misunderstanding of gravitational lensing.
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 Quote by ratfink Not really. This quasar, if it is 'behind' the galaxy, must be in a prime spot for gravitational lensing. Ergo if it is 'behind' the galaxy then it should be lensed with a few images. If it is 'in' the galaxy then there will be no lensing and hence no images. How many images are there of this galaxy? Answer: none! Ergo it is in the galaxy.
NGC 7319 would need to be both further away and more massive to produce strong gravitational lensing (i.e. multiple images) of this quasar.
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 Quote by SpaceTiger NGC 7319 would need to be both further away and more massive to produce strong gravitational lensing (i.e. multiple images) of this quasar.
Ah! very convenient!
I understood that single galaxies are able to produce strong gravitational lensing if one is "within a few arcseconds from the centre" - and low and behold this quasar is within a few arcseconds of the centre of NGC 7319. So why no lensing effects if the quasar is 'behind' the galaxy. Even if no multiple images, a little gravitational blurring would help to prove the case one way or another.
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 Quote by ratfink Ah! very convenient!
This is starting to smell trollish.

 I understood that single galaxies are able to produce strong gravitational lensing if one is "within a few arcseconds from the centre" - and low and behold this quasar is within a few arcseconds of the centre of NGC 7319. So why no lensing effects if the quasar is 'behind' the galaxy.
I already told you, it's not massive enough and it's too close. Gravitational lensing is much more effective when the lens is at moderate redshifts. Most galaxy lenses are ellipticals -- spirals, particularly face-on spirals, have a small or nonexistant lensing cross section.

 Even if no multiple images, a little gravitational blurring would help to prove the case one way or another.
Quasars are point sources, so they don't "blur" unless there are multiple unresolved images. Since this galaxy can't produce multiple images of the quasar, there will be no blurring.
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 Quote by SpaceTiger This is starting to smell trollish.
appologies, it wasn't meant to be.

 I already told you, it's not massive enough and it's too close. Gravitational lensing is much more effective when the lens is at moderate redshifts. Most galaxy lenses are ellipticals -- spirals, particularly face-on spirals, have a small or nonexistant lensing cross section.
"much more effective", is not the same as none at all. As stated earlier, single galaxies can act as lenses if the quasar is near the centre and this quasar is near the centre. Also how 'close' is 'close?' One can have nearby lensing systems - see here. I know that this is a large cluster but it is at a redshift of z = 0.042 whilst our lensing galaxy NGC 7319 is at a redshift of 0.0225 - only half as far away as a system known to produce lensing.

So we have a quasar close to a galactic centre (a situation known to produce lensing) in a galaxy half as far away from a lensing cluster (a situation known to produce lensing) so why not a little bit of lensing in our quasar?
Even a tiny tiny bit of unresolved images would do it (how about a couple of fuzzy bulges either side?). This would show beyond doubt that the galaxy is far behind the galaxy and lensed - and not inside it. No lensing means the quasar is inside the galaxy, mainstream cosmology needs to show lensing - or is there some other way to separate the two models?

 Quasars are point sources, so they don't "blur" unless there are multiple unresolved images. Since this galaxy can't produce multiple images of the quasar, there will be no blurring.
'can't' is a dangerous word to use in science and especially cosmology!
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 Quote by ratfink "much more effective", is not the same as none at all.
In the image of a point source, it is. Unless there are multiple images produced in the lensing, the point source will not be distorted. It will be magnified somewhat by weak lensing, but we wouldn't be able to tell.

 As stated earlier, single galaxies can act as lenses if the quasar is near the centre and this quasar is near the centre. Also how 'close' is 'close?' One can have nearby lensing systems - see here.
Well, as you say, that's a galaxy cluster, not a galaxy. Near the center, clusters have a much higher surface density and are much more capable of lensing quasars. If the source (quasar) is very far away, then in order to produce strong gravitational lensing, one needs a surface density larger than

$$\Sigma_c=\frac{c^2}{4\pi Gd}$$

A nearby face-on spiral, unless it's extremely massive, won't be able to produce this, so it won't produce multiple-image gravitational lensing. There will be weak lensing effects in the source, but unlike with galaxy sources, a quasar point-source image won't be distorted by it.

 'can't' is a dangerous word to use in science and especially cosmology!
You should probably stop putting in these little rhetorical comments. Do you really need me to explain why they're silly and illogical?
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 Quote by SpaceTiger In the image of a point source, it is. Unless there are multiple images produced in the lensing, the point source will not be distorted. It will be magnified somewhat by weak lensing, but we wouldn't be able to tell.
Oh. So it is either a point source or it is multiple images? In that case there must be a minimum angular separation between these images. Below this separation we have a magnified point source, above this minimum separation we have multiple images. Just out of interest, what is this minimum angular separation of the images of a lensed quasar?

 You should probably stop putting in these little rhetorical comments. Do you really need me to explain why they're silly and illogical?
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 Quote by ratfink Oh. So it is either a point source or it is multiple images? In that case there must be a minimum angular separation between these images. Below this separation we have a magnified point source, above this minimum separation we have multiple images.
No, below the critical surface density, there is only one image. Given infinite resolution, this image would be distorted, but quasars are never resolved in images like this, so they continue to appear as point sources.

The whole purpose of science is determine what is and isn't possible in the natural world and then quantify the behavior. If "can't" were a bad word in science, then we would be forced to answer every question in the affirmative. I don't know where you got your impression that we can't rule out things in cosmology.
 Emeritus Sci Advisor PF Gold P: 4,005 Detection of Cosmic Magnification with the Sloan Digital Sky Survey, by Scranton et al., is probably the most extensive study of the (weak) lensing of quasars by galaxies (and clusters). The Introduction to this paper includes a nice summary of the 'state of the art' prior to this paper. The CASTLES survey is one search for lensed quasars (an example of strong lensing), using the HST. The results of these, and other work, are quite clear - quasars are at cosmological distances, and the inferred space densities match predictions of the concordance cosmological models, within a sigma or two. AFAIK, there is no alternative theory that comes close to this degree of match (between observation and prediction), except (of course) those which predict essentially the same thing - in this space - as the concordance cosmological models. Here is the Galianni et al. paper on the NGC 7319 quasar. ratfink, if you'd like to do some independent research on quasars (esp the NGC 7319 one), lensing of quasars, or develop an alternative to the mainstream on quasars (or cosmology), please go ahead. When you're ready, PF's IR section is available for you to submit your work, should you choose to have PF's Science Advisors critique any such work. In the meantime, we welcome your questions and (mainstream) contributions on this topic.
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 Quote by SpaceTiger The whole purpose of science is determine what is and isn't possible in the natural world and then quantify the behavior. If "can't" were a bad word in science, then we would be forced to answer every question in the affirmative. I don't know where you got your impression that we can't rule out things in cosmology.
The reason I stated that 'can't' is a dangerous word in science is that scientists who, in the past, have said something 'can't' happen have always gone on to be proved wrong by observation!
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 Quote by Nereid ratfink, if you'd like to do some independent research on quasars (esp the NGC 7319 one), lensing of quasars, or develop an alternative to the mainstream on quasars (or cosmology), please go ahead. When you're ready, PF's IR section is available for you to submit your work, should you choose to have PF's Science Advisors critique any such work. In the meantime, we welcome your questions and (mainstream) contributions on this topic.
Sorry, my fault. I thought that this was a discussion board. I now see that it is not.
I thank you for you kind offer of a critique but, if you don't mind, I prefer to publish in peer reviewed journals. However, may I extend the same offer to yourselves at PF. Should any of you like any help or a critique of your work, just e mail me and i would be pleased to help out.
Please see my other post re posters acting as moderators.
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 Quote by ratfink Sorry, my fault. I thought that this was a discussion board. I now see that it is not. I thank you for you kind offer of a critique but, if you don't mind, I prefer to publish in peer reviewed journals. However, may I extend the same offer to yourselves at PF. Should any of you like any help or a critique of your work, just e mail me and i would be pleased to help out. Please see my other post re posters acting as moderators.
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 Quote by ratfink The reason I stated that 'can't' is a dangerous word in science is that scientists who, in the past, have said something 'can't' happen have always gone on to be proved wrong by observation!
We're looking at the observation. You said theory predicted something that contradicted the observation. I'm saying you're wrong. Now you're telling me the theory might be contradicted by the observation. It looks like you pick your cherries while spinning! Careful you don't pick any crabapples in your disoriented state.