https://www.legacysurvey.org//viewer/?ra=1.2145&dec=-1.0548&layer=hsc-dr2&zoom=16
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Odd one that
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canāt decide if itās lensing or notā¦
I would think so. Down in a bunch of catalogues as one.
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So bright
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cheers 
I agree that it is very odd to see such a prominent blue arc associated with no significant cluster of galaxies or even one particularly massive galaxy. But itās definitely there!
I also think itās slightly odd that the three galaxies upper left all appear to have the same morphology and alignment. This is definitely an odd one!
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It is a gravitational lensed image with a kown gravitational lens candidate.
Ine
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Yes, but itās still pretty unusual! What is lensing it?
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there are any of two galaxies that could be responsible for the lensingā¦even though it has all the attributes, my gut says it isnāt a g. lens which is why I posted it under 'beautiful/unusual objectsā¦
Thereās a fairly obvious cluster there. Cluster lensing can be pretty crazy.
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Maybe, but cluster lensing should produce an arc that is roughly centred on the centre of mass of the cluster, and that doesnāt appear to be the case here. Also, with such a dispersed cluster as this but such a strong lensing effect, I would expect the cluster to be lensing other objects too. Itās definitely out of the ordinary. I wonder if this might be lensing caused by a ārogueā wandering black hole, ie one not at the centre of a galaxy???
Iād like to see that one looked at by Hubble! 
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Itās possible it is lensing other objects, but this is the only one bright enough for HSC to resolve. As for centre of mass, I wouldnt feel comfortable estimating where that is lol, though iād note that cluster lensing can produce very odd shapes/configurations/positions. Weāre seeing this in glorious detail with JWST.
Odds of a random wandering black hole, firstly being capable of producing such a lens (would either have to be extremely close or extremely massive), but also happening to align with a galaxy cluster so perfectlyā¦ I think occamās razor probably comes in to play here.
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Agreed. alignment with that cluster and the properties it would have to have do seem to Occamās razorify the set of solutions.
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Yes, and someone else always wins the lottery, too.
Iām looking at the morphology and trying to account for it through physics, not probability. If you can explain how such an extremely bright gravitationally lensed object can appear, in the absence of any others bright enough to be resolved by HSC, adjacent to what by any objective assessment has to be a not particularly dense galaxy cluster, then Iād be very interested in hearing the explanation.
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Much like this example, Iād imagine:
You can see how lower resolution would mean only one lensed image is likely to be resolved (the bright one top left of centre).
If this was caused by a wandering BH, it would have to either be supermassive and mysteriously have no visible material in orbit, or stellar mass and close enough to climb in to bed with us (pretty sure stellar mass black holes have only been observed to cause microlensing, but I may stand corrected).
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The spectroscopic redshifts from the arc and one of the cluster galaxies work out for a lensed imaged (the lensed image having a much higher redshift)
I agree with that the cluster looks very light to produce such an image, and personally I had doubts because of the thickness of the arc, not being a regular slicer of an arc.
Part of the issue probably is that the lensed galaxy is starforming / starburst so it looks brighter than others.
Perhaps also something weird is going on with the infamous āDark Matterā in this case?
PS at least it looks happy : )
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If a single galaxy can produce a lens like this:
I donāt think its inconceivable that even a small-ish cluster could produce the lensing effect in the OPās post.
I think the thickness of the arc is generally a result of viewing geometry? It certainly looks very bright, and starburst could definitely be a reason.
Haha, I try to not think about Dark Matter as much as possible 
It kinda breaks my brain 
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Ha I have my own little (as of yet unquantified) little stickhorse crank theory about that.
But I donāt want to derail this thread and besides, Iāve already heard enough about that it canāt work and why not from too many people so I guess thatās that 
no more bashing needed 
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Assuming a simple center of mass instead of something complicated that has to be modelled, I think this is the smallest position of center of mass possible.
I think larger circles would probably fit the arc but then the center of mass for the lensing would get so far away it is pretty much illogical. (likely though the circle has a too small diameter)
The weird thing is I canāt see any other kind of lensing effect around this area. Not even a counter-image hich I guess should be visible from such a bright lensed galaxyā¦
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