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Lensed quasar pair

  1. May 13, 2005 #1

    turbo

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    "lensed" quasar pair

    Here is a paper about a purportedly lensed quasar.

    http://xxx.lanl.gov/abs/astro-ph/0505248

    Has anybody notice how "lensed" quasars, like those comprising the Einstein cross, seem to manage to retain their point-like appearance instead of exhibiting arc-like distortion around the center of mass of the "lensing" mass? Why is this? Can light from quasars blithely ignore the laws of classical optics? As a board-certified optician, I would find it difficult to build you any lens (short of combinations of basic prisms) that would give you multiple images of a point object and retain their point-like appearance with no smearing. How do these "lensing" clusters and galaxies manage to accomplish this preferentially along the line of sight to US?
     
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  3. May 13, 2005 #2

    Chronos

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    Concerning the referenced paper, it is not clear this is a lensing event. From the abstract:

    we revisit the long-standing question of whether this quasar pair is a binary quasar or a wide-separation lens.
    and
    Unless the mass-to-light ratio of the galaxy is at least 80 times larger than usual, the lensing hypothesis requires that the galaxy group or cluster plays a uniquely important role in producing the observed deflections.

    Image distortion in lensing events is largely a matter of alignment
    http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/43/text/
    A gravitational lens is produced by the enormous gravitational field of a massive object which bends light to magnify, brighten and distort the image of a more distant object. Depending on the alignment between the objects and the mass distribution of the foreground lens, the more distant object can be smeared into arcs or split into pairs, triples, or even quadruple images.

    http://www.mira.org/newsletr/nlsum97/gravlens.htm
    The best known type of lens occurs when light from a distant quasar (source) is deflected by close passage to a single galaxy (lens). In this case, the result appears to be several identical quasars located very close together; these usually occur as double, triple, and quadruple images of the same source. In addition to these multiply imaged objects, gravitational lenses can also appear as arcs and sometimes even complete rings of light! Arcs and rings are generally made when light from very distant galaxies passes through massive clusters of galaxies (arcs), or when a quasar is precisely aligned with the center of a single galaxy (rings).
     
  4. May 13, 2005 #3

    SpaceTiger

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    Do you mind being more specific about which laws you think are being violated? I don't see any reason why a light beam couldn't be split into multiple images (without distortion) in the laws of GR.
     
  5. May 14, 2005 #4

    turbo

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    In classical optics, it is easy to produce point-like multiple images of a point source. The solutions to these problems involve prism-like refractive media with relatively planar density transitions (think of a faceted gem). Trying to produce point-like images with refractive media like the lenticular or spheroidal fields surrounding galaxies or the more complex fields of clusters is impossible. The field densities and the shapes of the fields cannot possibly conspire to produce perfect point-like images preferentially along the line of sight to us. The images of the "point-like source" (quasar) will be smeared radially, axially, or both and will not appear point-like.

    GR is valuable and predictive on a variety of scales, but it cannot trump optical principles that were proven centuries ago and are used to validate GR today. Some GR adherents say that the Einstein cross is a perfect case of gravitational lensing (with no explanation of how GR accomplishes this amazing feat), but in the next breath they say that if a galactic core is on the line of sight to a quasar, the quasar will appear as a ring (which is FAR more likely in classical optics). The members of the Einstein Cross are point-like, with no real axial or radial distortions, AND the light curves of the four elements have diverged in significant ways over the years. They are most likely four individual objects that have been ejected from the core of the "lensing" galaxy. The fact that the objects have excess redshift with respect to the galaxy prohibits GR believers from believing that they can be physically associated with it. This is puzzling to me, since we have known for decades that very dense objects exhibit intrinsic redshifts. If black holes accrete in galactic cores and are perturbed out of the core, their accretion zones should exhibit extreme redshifts, especially if the accretion zones are very close to the event horizons.
     
  6. May 14, 2005 #5

    SpaceTiger

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    None of what you've just said actually shows which part of the math is wrong. I've seen the solutions of these equations actually derived for multiple quasars, so if you're going to dispute that, you'll have to show the problems with the derivation.

    You have to remember that quasars are VERY point-like. The majority of the emission comes from a region less than a tenth of a parsec in size, while the quasars are gigaparsecs away. This means that, in the absence of perfect alignment, the actual "smearing" will be difficult to detect (though it does occur). This is why people have been thinking about using microlensing to study the properties of the quasar emission region. The magnifications in microlensing are so large that the quasar might actually become resolvable. See this paper, for example.
     
  7. May 14, 2005 #6

    Chronos

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    Your insistence the images cannot be pointlike remains unfounded. You would think a few scientists are sufficiently competent to have recognized and written a paper detailing any violations of optical physics commited by these images.
    Interesting. What evidence of physical association between the 'ejected' quasars and the 'mother' galaxy do you have in mind? Why would radiation only be emitted near the event horizon? Accretion discs must be continuously replenished by infalling matter. Would you not think this infalling matter would become highly luminous long before it got anywhere near enough the event horizon to attain the huge redshifts you are suggesting? Would you expect this radiation to be blindingly bright compared to the pitiful squawk of photons emitted near the event horizon?
    Indeed, they have. In fact, this data can be used to calculate the distance of the lensed quasar independent of its redshift. You may find this interesting:
    http://www.mira.org/museum/lens.htm
     
  8. May 14, 2005 #7

    turbo

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    Hi, ST. Let me first say that that with objects that are VERY point-like (your words) we should expect some optical effects that will shed some light on the nature of the "lensing" involved. The more point-like the source objects, the more critically we can examine the image(s).

    The next thing that we have to look at is whether the distortion of the shapes of the observed objects can be significantly changed by the geometry of the source-lensing object-observing frame relationship. This is a tough one. How can a "distant" object end up being "multiply imaged" by a lensing entity instead of being smeared? There is no critical break-point in any models that I have found that can can suddenly result in multiple point-like images of a quasar when a quasar is lensed by a galaxy.

    It is incumbent on the GR folks to explain how GR "optics" demonstrates how the Einstein Cross can be an example of optical lensing. If, (as I believe) it is an example of a four high-redshift bodies embedded in a low-redshift galaxy, somebody is going to shake the hand of the king of Sweden over this one. It would be a real shame if it happened only after all of us were pushing daisies.
     
    Last edited: May 14, 2005
  9. May 14, 2005 #8

    SpaceTiger

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    http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1994A%26A...284..285K&data_type=PDF_HIGH&type=PRINTER&filetype=.pdf

    Section 3.4
     
  10. May 15, 2005 #9

    Chronos

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    Did you read the links ST and I have offered? Does it not appear you resort to vague generalizations when confronted with hard questions?
     
    Last edited: May 15, 2005
  11. May 15, 2005 #10

    turbo

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    The approach of the paper is interesting, but it fails to explain how four images of a distant point-like source can be accurately reproduced as point-like images symmetrically spaced around the core of a lensing galaxy. The multiple-image effect might be a wonderful explanation for the production of mirror arclets (seen in real examples of galactic or cluster lensing), but it does not address the question of how the lensing galaxy can provide perfectly-focused multiple images of the lensed body. This raises the questions of "why are we at the correct focal length to see these wonderful images focused so nicely?" and "why are we on the correct line of sight to see these images at all?".

    You will note that the authors repeatedly state that modeling the gravitational lensing effects of bodies with elliptical mass distributions is problematic.

    Here is a physicist (Matthias Bartelmann) with a proper understanding of optics and lensing.

    http://www.mpa-garching.mpg.de/mpa/publications/preprints/pp2003/MPA1552.pdf

    Here is a quick-time movie of a gavitational lens by the same author.

    http://spiff.rit.edu/classes/phys240/lectures/grav_lens/GL_4.qt
     
    Last edited: May 15, 2005
  12. May 15, 2005 #11

    turbo

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    Unfounded? Are you aware that the "lensing" galaxy of the Einstein Cross is a barred spiral and not a homogeneous lenticular body? Do you know how little asymmetry in the shape or density of refractive media to produce severe distortion? I do, having supplied thousands of people with lenses designed to compensate for the astigmatism caused by the distortion of their eyes' lenses. I do not need a peer-reviewed paper from an astronomer to teach me basic optics. Finally, it should not surprise you that there are not a raft of peer-reviewd papers questioning the nature of the Einstein Cross. Such papers would land the authors in the same dog house that Arp is in, IF they got past the referees.

    Well, the most obvious sign of physical association is the location of the quasars around the nucleus of the host galaxy. If you search Google Scholar on "radiation recoil" you will find any number of papers modeling the ejection of black holes from galactic nuclei.

    If a black hole is hurtling through a galaxy, I expect that it will be stripping materials along the way. This is not equivalent to the behaviour of a BH that condensed in place and has had millions of years to develop a large stable accretion disk.

    Can you explain the light curves of the four components in your lensing model? You will note that objects B and C have been trending in opposite directions (in luminosity) for a number of years. Not shown on that MIRA page are the color differences between the four objects and their changes over time.

    http://vela.astro.ulg.ac.be/themes/dataproc/deconv/articles/q2237/q2237.html#len

    Here is another paper that examines the infrared hump surrounding the four objects. Their conclusion is that the quasar's light is being absorbed and reradiated by dust. This is easy to believe if the quasars are actually embedded in the host galaxy.

    http://www.atnf.csiro.au/pasa/18_2/agol/paper/node4.html

     
  13. May 15, 2005 #12

    turbo

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    When people respond with links, I read them. In the case of papers, I try to follow relevant citations as well, which takes time. I explain my reasoning as clearly as possible and I try to find applicable reasearch to illuminate my answers. If these answers are "vague generalizations" to you, then maybe you are not understanding the relevance of the answers, or are simply dismissing them out of hand as "crackpot", "cowpie", without even thinking about them.
     
  14. May 15, 2005 #13

    turbo

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    http://citebase.eprints.org/cgi-bin...pdf&identifier=oai:arXiv.org:astro-ph/0301592

    Here is a paper documenting Chandra observations of the Einstein cross. Interestingly, Object D may actually be 2 separate objects.

    Most interesting, they observed a broad Iron/Potassium alpha emission line (99.99% confidence level) ONLY in object A, not in B,C,D1,D2. The authors suggest that microlensing could account for the appearance of the emission line, although not very entusiastically or convincingly.
     
  15. May 16, 2005 #14

    Chronos

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    Irrelevant.
    Writing unsound papers tends to have that effect. Suppose we assume the lensing galaxy has a central black hole that does most of the lensing. Would that tend to make the images a bit more focused? Furthermore, the images are not undistorted when sufficiently magnified. Take another look at the images in the paper you cited. You can try these as well:
    http://articles.adsabs.harvard.edu//full/seri/AJ.../0095//0999999P096.html
    http://www.journals.uchicago.edu/Ap...5373.web.pdf?erFrom=-4166844869564147657Guest
    The associated papers are also worth reading.
    Line of sight is irrelevant. More importantly, how does an ejected black hole manage to drag an accretion source along with it?
    Good point. So where are the pictures of quasars still within the ejecting galaxy?
    I don't have a model, unless agreeing with the preponderance of evidence constitutes a model.
    I fail to see where, or how this suggests the images are separate objects.
    It is also easy to believe if the quasars are behind the lensing galaxy. How would the dust know how far away the light source was?
     
  16. May 16, 2005 #15

    turbo

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    If you think that the asymmetry of the lensing media is irrelevant to the images produced, you might want to do a little reading about optics.
    Line of sight is absolutely critical, as you would know if you will spend a little time reading about lensing. You might want to download this free program. You will see that alignment offsets of as little as .01 arcsecond produce noticeable changes in the appearance of the lensed image.

    http://www.kwakkelflap.com/gravlens.html

    Now, you're starting to catch on. A BH slinging through a galactic disk cannot develop and drag along a stable accretion disk. Its relationship with the material that it accretes will be predominantly collisional.

    When you look at the Einstein Cross, you will see the best example known to us.
     
  17. May 17, 2005 #16

    Chronos

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    A lively and fun exchange! Let's just cut our losses and agree to disagree. I am the dour mainstreamer and you are the rebel. We will never convince the other to convert. It's still fun to clash.
     
  18. May 17, 2005 #17

    SpaceTiger

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    Actually it does, do you understand the equations presented there?


    I already addressed this. A perfect point source will not be distorted at all because it will only satisfy their equation (equation 35) at specific points. A nearly perfect point source will experience a distortion that depends on its actual angular size. Since the physical size of the emission region is so small, there's no reason we should expect to be able to resolve this distortion for quasars. The images will look like point sources.


    A point source cannot be said to be "focused" at all because it's not resolved. If we had infinite resolution, we would see a distorted image of the broad-line region smeared over milli- or micro-arcseconds (probably in arc shapes), but we don't have those capabilities. We do see such arcs in lensing of galaxies because galaxies aren't even nearly point sources on arcsecond scales. For quasars, as far as our instruments can tell, the sources are points.


    They state that the models are unphysical only for high axis ratios, and this has nothing to do with the lensing, just gravitational stability. If you put a small value of f into equation 35, you'll get a result that's perfectly physical.
     
  19. May 17, 2005 #18

    turbo

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    I follow how they calculate the positions of the critical images. What I don't see is how perfectly-focused point-like images result at these locations.

    Can you explain this effect? The vast majority of the stars in our sky are point-like in ANY instrument that we can image them in. If the optics of the instrument are not perfect, these point-like images will be distorted. We might expect to see shear (arcing) coma (radial flaring off-axis) astigmatism (induced by cylindrical aberration in some preferential direction) or any number of distortions in the image, depending on the asymmetry of the lensing media. Perhaps I am just really obtuse, but I cannot for the life of me understand how galactic lenses can violate these rules when clusters obey them implicitly.
     
  20. May 18, 2005 #19

    Chronos

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    They can't be explained, turbo-1, when you refuse to accept any reasonable explanation. Pardon me for being blunt, but your argument appears to be a wind chime.
     
    Last edited: May 18, 2005
  21. May 18, 2005 #20

    turbo

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    Just give me a reasonable explanation, then, and we'll be done with it. You quote sources that touch on the subject tangentially, then claim that I refuse to see the truth (do I see a pattern here?), but you seem to have trouble producing an explanation of how a lensing galaxy can produce four point-like images of a background object. I fully expect (given your combative nature) that you have searched for just such a citation, and have come up short. Why is that?

    Earlier, you told me essentially that I must be wrong because there haven't been papers published supporting my view. This is a bit silly, don't you think? It's like saying that everything that can be known is already known and accepted by people smarter than me, so I should stop asking questions and trust that "other people" are taking care of real science. The fact that other people have uncritically accepted the "lensing" explanation of the Einstein Cross is not proof that it is an example of lensing. Acceptance of this kind of "proof" is simple herd behavior - it has no bearing on the validity of an idea. Scientists have uncritically accepted things for decades, even centuries, that we now believe to be wrong. Are we at a perfect age, in which all the mysteries are solved? When did this happen? I must have missed the press release.

    To get back to the subject: should we believe that somehow, there are four nearly-perfect preferential paths that light from a quasar gigaparsecs away can follow around this lensing galaxy on its way to our eyes? I do not believe that, and cannot find a way to reconcile that with what I know about optics. If you can supply a relevant citation (addressing the focused discrete images), I would be grateful. If the paper also explains how only object A has a broad emission line in the Fe/K alpha while objects B,C,D (and perhaps D2, if the Chandra observations are to be believed) do not, you will get a gold star.

    I will cheerfully ignore simple naysaying, carpet-bombing with irrelevant citations, and insults regarding my mental abilities (as always) - just give me a relevant citation. You are dead-certain that I am wrong and have said so in enough ways - now prove it.
     
    Last edited: May 18, 2005
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