Space Warps Talk

  • migeon by migeon

    I'm new at spotting lensing and I missed this one. Is the giveaway the single bright blue spot to left of the galaxy? If so, why just a single light?

    Posted

  • Capella05 by Capella05 moderator

    The counter image is embedded in the galaxy - not intentionally!

    Sometimes the simulated lenses are slightly off center, as they are created by a program using data from a database. When the data is incorrect we get a somewhat strange sim that we call a simfail 😃

    Have you read this blog post - it has more information about the sims.

    If you have any other question about them, please feel free to post them here!

    Posted

  • anupreeta by anupreeta scientist, admin

    While what @Capella05 is making you aware of simfail cases, Please note that this kind of cases are not simfail.

    In real lenses, when the background galaxy is off-centered with respect to the foreground yellow galaxy (like the one shown here), you will form two lensed images of the background galaxy but they are at asymmetric distance from the lensing yellow galaxy. Also, the farther one is much brighter whereas the image closer to the lensing galaxy is much fainter. So, the combination of proximity and faintness of the second image to the yellow galaxy makes it difficult for such "double" lens images to be found.

    These kind of double lenses are inherently difficult to detected for the reasons stated above. Therefore, we need to be extra careful when you find such candidates, please use the tools in Quick Dashboard to see if you find any hints of a second similar looking lensed image on the other side of the galaxy by changing contrast/brightness/zoom etc.

    Hope this helps!!

    Posted

  • mudkip201 by mudkip201

    I think the second one has actually been placed on top of the galaxy itself.

    Posted