Space Warps Talk

Lenses masquerading as ring galaxies?

  • robert_gagliano by robert_gagliano

    Ring galaxies are rare. I could find only 2 catalogs on VizieR (Butat+,1995 and Madore+,2009). I think it is possible that a lensed galaxy could masquerade as a ring galaxy. It might make an interesting side project if the science team could do a coordinates crossmatch with the CFHTLS data and these 2 catalogs and let us check the images to see if any of the galaxies classified as rings may in fact be lenses.

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  • psaha by psaha scientist in response to robert gagliano's comment.

    The ring galaxies in those catalogs are comparatively nearby, and hence large on the sky. For example, Buta's catalog gives 0.6 arcmin for a typical ring diameter. You do occasionally see galaxies that big in Spacewarps, like say ASW00004of but at that kind of zoom they look very different from lenses.

    Interestingly, Buta in his paper used "lens" and "ring" as synonyms. In that context, "lens" is an older terminology, and does not mean gravitational lens.

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  • c_cld by c_cld

    Lens from Buta's terminology is still used:

    A recent catalog by Preethi B. Nair and Roberto G. Abraham published 2010 February 3 in ApJS

    VISUAL MORPHOLOGICAL CLASSIFICATIONS in SDSS gives 532 "lenses" classifications for 14,034 galaxies in SDSS DR4.

    So beware of key words and do prefer "strong gravitational lens" to avoid misinterpretations we still have for example with "ring" and "ringed" in GZ forum.

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  • c_cld by c_cld in response to robert gagliano's comment.

    Your title should be inverted

    'Ringed galaxies masquerading as Lenses'?

    imagine ASW00010pg NGC 809 shifted from close redshift 0.018 to redshift 0.3 - 0.7 as we try to sort out these galaxies in SpaceWarps.

    Would we tag it #no_lens, but a surrounding fuzz?

    NGC 809

    only zoom-out (terapix access)
    terapix

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  • robert_gagliano by robert_gagliano

    I found 2 additional catalogs on VizieR. Faunday-Abans+, 1994 and Moiseev+, 2011. The later are SDSS images for 275 ring galaxies classified by the Galaxy Zoo. In total all the mentioned ring galaxy catalogs probably represent only a few thousand images to check, a drop in the bucket. The visual resemblance between some of the images of ringed galaxies I have seen and our strong gravitational lenses is striking. I can see how a few may have been misclassified. The percent yield may be better than checking hundreds of thousands of random images.

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  • c_cld by c_cld in response to robert gagliano's comment.

    Recall Galaxy Zoo The First Polar Ring Galaxy Atlas , in three OOTDs from Jean Tate based on a recent paper by Moiseev et al. (2011) arXiv:1107.1966
    You could see all images studied (most posted by zooites) which didn't yield any gravitational lenses.

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  • robert_gagliano by robert_gagliano

    Again, I don't think we can conclude there are no strong gravitational lenses lurking in the catalogs, papers or lists of ring galaxies (polar or non-polar) unless we do a coordinates crossmatch with our CFHTLS images and check all those matches ourselves. Think I'm beating a dead horse if there is no interest from the science team.

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  • c_cld by c_cld in response to robert gagliano's comment.

    The only cross-match between Moiseev's atlas and CFHTLS fields is ra=14 24 43.86 dec=+53 51 50.6 16.11 9 (Table 2: SPRC '143' object ). All others coords are outside the Wide fields.

    polar ring terapix access

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