Galaxy Zoo Talk

'Do the clumps appear to be imbedded within a larger object'

  • planetaryscience by planetaryscience

    That's the question you get on the classification tree once you've clicked the 'does the galaxy have a mostly clumpy appearance' classification. I've been having trouble answering it, mainly because it didn't make much sense... What does it mean "imbedded within a larger object" ? And how do I know when it's that versus something else...?


  • JeanTate by JeanTate

    I'm a bit surprised that it's been four days since you asked this - excellent! - question, planetaryscience, and no one has answered.

    My own view is that this is one of the least objective parts of classification exercise, relying as it obviously does on each zooite's subjective interpretation. Within the context of 'leading edge' astronomy, for astronomers who work on galaxy evolution beyond the local universe as evidenced by morphology (i.e. in Hubble, not ground-based, images), the question intends to get at whether high-z galaxies appear a) clumpy and b) clumps within a fainter, diffuse structure.

    Historically, this question is descendant of one of the earliest findings of deep Hubble images; namely, that the many itty-bitty blue blobs imaged back then turned out to be 'merely' regions of intense star-formation within larger structures ('galaxies') at high redshift. But maybe many 'clumpy' things are not galaxies? Maybe they're more like separate, dwarf-sized galaxies which are close to each other/merging? My guess is that this classification question is trying to shed objective light on that question.

    Perhaps a concrete example might help.

    Consider SDSS DR7 ObjId 587741532789866544:

    enter image description here

    It's a very nice, face-on spiral galaxy with a bright nucleus, a small bulge, and many regions of star-formation in - and between? - its arms.

    Now if this were viewed at high redshift, through the CANDELS filters, what would you see? Very likely a 'mostly clumpy appearance' object, and the clumps would 'appear to be embedded within a larger object'1. That, I think, is what the question is getting at.

    But without this background, and with the expectation that ordinary zooites' subjective interpretations are sufficiently similar that statistical analyses of the clicks will be meaningful ๐Ÿ˜‰

    So, the short answer to your question would seem to be: "whatever you think it means".

    1 or not; but if the star-formation regions were bigger, and brighter? then likely yes


  • planetaryscience by planetaryscience

    Thanks for the information, very informative... ๐Ÿ˜• ๐Ÿ˜ƒ Anyways, so it's specifically for when the galaxy seems to have nebulosity around it that can't be easily explained as "that galaxy," if you know what I mean?


  • zutopian by zutopian in response to planetaryscience's comment.

    When you click the Help button at that question on the classification page, following text is displayed.:
    "Look carefully for faint background light surrounding the clumps - are they embedded in a visible galaxy?"
    Besides there are shown 2 images.: One for Yes and one for No.