Lensed Quasar Pair: Retaining Point-like Appearance

[Chronos]

Nothing wrong with questions, turbo, and they are interesting. We should, however, remain focused on observational evidence. In the case of the Einstein cross, there is a great deal of good evidence it is a gravitational lensing event - emission and absorption lines, microlensing, time delay in brightness fluctuations, and redshift correlations. Physicists are not disturbed by the absence of any apparent distortion in lensed, point-like sources - like a distant quasar. You can recreate this effect with a pinhole camera. I hand polished a short focus Newtonian mirrer once. Pits in the reflective surface can produce these kind of images when viewed off axis. Try some ray traces and see if you can find a configuration that gives multiple, point-like images from a point source. Anyways, I think your point is sufficiently interesting to do some digging... so I spent the evening mining. This is all I came up with so far:

http://nedwww.ipac.caltech.edu/level5/Mellier/Mellier2_1.html
Note that for a point-like object like a QSO, the total amplification of light and the image position will be the only observable parameters.

http://astro.ic.ac.uk/Research/Extragal/
A gravitational lens can form multiple images of the source. These are point images for a point source such as a quasar, but a galaxy, being extended, is lensed into arcs or a ring.

http://www.jb.man.ac.uk/research/gravlens/intro/intro.html
If the line of sight to the quasar passes exactly through the galaxy, the symmetry of the system results in the formation of an ``Einstein ring''. If the line of sight is slightly off-centre, this produces multiple point images

http://folk.uio.no/kjetikj/science/master/description.html
Illustrated in above is a typical case of gravitational macrolensing, a galaxy is situated between us and a remote quasar, and we observe several images. In fact, it can be proved that there will be an odd number of images, but also that we will almost always see just an even number of images because one image will be heavily demagnified.

 

[turbo]

Nothing wrong with questions, turbo, and they are interesting. We should, however, remain focused on observational evidence. In the case of the Einstein cross, there is a great deal of good evidence it is a gravitational lensing event - emission and absorption lines...

Please see the paper I linked above regarding Chandra observations. Object A exhibits broad Fe/Kalpha emission lines and the remaining objects do not. It would be easy to explain how object A might have absorption lines that the other objects do not (using the light-path explanation), but if these are all images of one lensed object, they should all have the same emission spectra, even if the absorption lines differ.

I helped a friend build a deck today - now mining for papers (with heating pads on my old achey knees).

 

[Chronos]

Will review. I ran across some stuff the other day related to that, but really didn't digest it. No doubt there are lots of ideas lurking about. Physics as usual keeps plenty of escape pods handy - I hope jumping out of your chair did not aggravate your knee issues. Old age is not for the faint of heart. I lugged around a bunch of pool sand bags around yesterday and I'm still breathing hard.