HIgh redshift arc? Model needed to add plausibility
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by drphilmarshall scientist, admin
We (@aprajita and I) think this could be a high redshift galaxy, seen magnified and lensed into a long arc. If this is the case, we might expect there to be a faint red counter-image on the opposite side of the right hand "lens" galaxy - but a model is needed to predict it's brightness. Maybe its suppressed, by the presence of the second lens galaxy? Plus there's that third yellow galaxy to the North-West...
Another question: is this more likely to be a small red galaxy lensed into three merging images that form an arc? Or a larger red galaxy distorted into a single feature?
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by Capella05 moderator
Hey Phil and Aprajita 😃
I will give it a bash - as I am sure both Els and Claude will. I will PM some of the other volunteers that have modelled in the past.
Any new modellers out there - that would like to give it a try?
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by ElisabethB moderator
Spagettifying as we speak ! 😄
First attempt : 9811
Contour map and mass distribution look reasonable.
Arc still too long and counter image too bright.
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by ElisabethB moderator
After some tweaking I got this : 9827
The arc is shorter and the counterimage fainter.Contour map and Mass distribution look clean
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by Capella05 moderator
I still have a bit of work to do on this model 9833
I think Phil is right, I think it may be a single larger galaxy lensed into 3 merging images.
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by Capella05 moderator
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by drphilmarshall scientist, admin
Good - fun to start with the quad option! I moved the middle image down to match the bright central knot, and the counter-image in a bit to make it fainter. Here's the result:
I think the counter-image needs to be even more central - and adding the third lens might help straighten up the arc.
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by Capella05 moderator in response to drphilmarshall's comment.
I have tried adding a third minima on the right, It did not appear on the overlay. So, I think there may be a tiny bug - I will email Rafi about it in the morning.
Apart from that it seemed quite plausible - wished I had saved it! I will return tomorrow to try again, I now need my sleep 😃
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by Budgieye moderator
from ElisabethB 9811, moved centre of mass to left, and added another point mass on the galaxy to the left. Maybe it is pulling the arc out of shape. Or is it too far away?
http://mite.physik.uzh.ch/lmt.html?rid=9811Posted
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by Capella05 moderator
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by c_cld
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by Budgieye moderator
I like that, C_cld, you made the arc nearly straight.
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by c_cld
ASW0006gwi 9917 Revised in #Model 9958 adding circular mass for the left ringed.
Doesn't change the reconstructed lensing system...Posted
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by ElisabethB moderator
Sorry, but I had to share this : ever see a square model ? 😄
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by ElisabethB moderator
On a more serious note : 9988
Contour map and mass distribution look a bit iffy
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by drphilmarshall scientist, admin in response to ElisabethB's comment.
This is an interesting model: 5 merging images would imply a rare "higher-order catastrophe" configuration, which are famous for providing very high magnification. I would love to know how much the source has been magnified in this synthetic image! The area in the source plane in which you can put a source and get 5 images is typically very small, so such lenses are expected to be rare - but then, the high magnification might make the system easier to observe so... Let's make a note of Els' model while going back to the more common (and so more likely) 3-image arcs!
PS. @rafael_kueng, any idea why the conjugate image points not match the peaks of the synethetic image brightness distribution? It doesn't look like a simple pixel offset bug...
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by c_cld in response to drphilmarshall's comment.
@phil Where do you find 5 images in Els model 9988?
As we ask Rafi to put the marks max, min, saddle and mass from the input, for me the reconstructed image is only a superposition of marks and Original SourceDiffPlot smoothed.
I see only two clumps on the arc and one faint counter image. Right?Posted
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Hi i thought i would also give it a go this is my attempt http://mite.physik.uzh.ch/data/010089
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by Capella05 moderator in response to Star hunter 1's comment.
Hi Star Hunter 😃
That is actually quite a good model. Contour map and mass distribution are both smooth, the synthetic image seems quite accurate.
You are going to put some of use old timers to shame!Posted
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by ElisabethB moderator
Yeay ! We have a new modelling recruit ! 😃
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by Star_hunter_1 in response to Capella05's comment.
Thankyou 😃
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by drphilmarshall scientist, admin in response to C_cld's comment.
@C_cld: Els set up her model with 5 conjugate points (green and cyan) marking out the arc - I thought these were taken by SpaghettiLens to be the positions of the multiple images of a background point source, no? The synthetic image is made (I hope) by putting a small extended surface brightness distribution in the source plane and then mapping this into the image plane using the deflection angle maps - although given the offsets between input points and output synimage, I'm afraid that last part might not be true...
Hello @Star_hunter_1! 😃
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by c_cld in response to drphilmarshall's comment.
With result data query on models you could see SL had n_images=6 (3 "sad" + 3 "min") but, to me, no results give a proof of 6 lensed reconstructed images from input assumptions.
My model 6758 shows more the 6 clumps close to the input image ASW00054l3 than Els model 9988 shows 6 over 2 clumps of ASW0006gwi.
I thought the synthetic image was a simple smoothing of advanced "Original SourceDiffPlot" made as you mentionned, so the superposition with input marks could be problematic.
To be followed up by the team...
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by Budgieye moderator
What do you call it a high redshift arc? Red arcs come from lensed galaxies at z=0.08? or so. If it was z=5, it wouldn't be an arc, it would be quasar points.
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