Space Warps Talk

How big are the lenses we are looking for?

  • kipi by kipi

    I am trying to understand what is the angular size of the objects that can be identified as lenses in the photos we are being presented here.
    Most simulated lenses we are exposed to are fairly big. Should we try to detect smaller ones like the pairs of tiny red and blue ones in the middle of this field ?

    Posted

  • ElisabethB by ElisabethB moderator

    The pairs of red and blue ones here are definitely not lenses.
    But you could look for very faint arcs not too far from big galaxies.
    As a rule, the lensed galaxies will be pretty close to the lensing galaxy.

    Posted

  • Budgieye by Budgieye moderator

    Wide separations are about 20" for a single galaxy
    For galaxy clusters, it may be 60"
    Small separations, those small annoying ones curled around a nucleus will be 1" or less.
    So most that we would see would be 2" or 8"
    I'll try to find out how wide our images are, but I think they look about 100" wide.

    Extremely distant (and therefore small) lenses would be hard to see at the resolution of this telescope, so I wouldn't worry about them unless they are an extremely bright colour. We can't see normal galaxies, because the telescope can't detect the light from them (too redshifted) so what you would look for are green, orange, yellow or red quasars. They would look like sets of bright small stars, very close together.

    Yellow lensed quasars have been found, at z=3.626, see
    Zooite Guide to Strong Gravitational Lenses
    SDSS J125418.94+223536.5
    SDSS J125418.94+223536.5

    There is a yellow lensed quasar in the Spotter's guide

    Posted