Space Warps Talk

Silly questions

  • AlexandredOr by AlexandredOr

    When we get this tag : Nice! There is no gravitational lens in this field! after studying an image, does it mean a contrario that in the other images, non tagged with this "Nice! There is no gravitational lens in this field!" there is inevitably one, or more, lens ??

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  • ElisabethB by ElisabethB moderator

    No ! 😄
    There is a subset of 600 (I think) images that have been carefully looked at by the scientist and they decided there was not a lens in them.
    These images are also part of the training.

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  • AlexandredOr by AlexandredOr

    Thank you Els 😄

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  • FBloggs by FBloggs

    Is it the whole sky that we are looking at or just particular sections?

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  • AlexandredOr by AlexandredOr

    Good question ! I'm impatient to know the answer... 8D

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  • Capella05 by Capella05 moderator

    Just a particular section of the sky 😃

    You can find out more information here CFHTLS Survey

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  • AlexandredOr by AlexandredOr

    Thank you Capella05. Here is the answer : CFHTLS is a survey conducted with the CFHT 3.6m telescope using the Megacam camera. It targeted 4 patches of the sky, adding up to about 150 sq deg It's finally a very short piece of sky we are studying !

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  • AlexandredOr by AlexandredOr

    Another silly question : when arcs are not too close to the lens, must we mark them too ? 😕

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  • Budgieye by Budgieye moderator

    I think the software wants you to mark the arcs, not the centre galaxy.

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  • ElisabethB by ElisabethB moderator

    I think Alexandre is asking about marking arcs that are far from the lensing galaxies.
    For me, if an arc is too far away, it cannot be a lensed arc and I won't mark it.
    Unless the lensing galaxy is very very massive, arcs will be close to the galaxy.

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  • AlexandredOr by AlexandredOr

    Thank you both of you. 😉

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