Radio Galaxy Zoo Talk

IR AND RADIO MAPPINGS

  • colin826kennedy by colin826kennedy

    There are many examples where the radio and IR mapping overlap with one of the radio sources, but where the IR image is much larger and does not seem to be physically associated with the radio contours. Can one ignore these or should one mark them anyway? ARG0000ssh is perhaps not the best example.

    Colin

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  • JeanTate by JeanTate in response to colin826kennedy's comment.

    Hi Colin.

    Here's my, ordinary zooite, view; should any part be wrong, I hope a scientist will jump in. Quickly.

    There are quite a few different reasons why the IR source which seems associated with a radio source will appear bigger; for example, the IR source may be a quite nearby galaxy (so appears quite big), or it may be several different sources but so close together (on the sky) that they appear one in the IR (this seems to be the case here). Sometimes the IR source is a bright star, which appears big only because it's bright.

    The physical association between radio sources and IR ones is one of the things which RGZ is hoping to get a much better handle on. And your judgement, and that of your fellow zooites (each RGZ image will be classified many times, independently), is what we're after ... if you think there's a physical association, then classify that way; if not, then not.

    For example, a fairly weak, somewhat extended set of radio contours may appear in the middle of a large oval-shaped IR source; this is very often radio emission from supernovae remnants (etc) in the plane of a nearby spiral galaxy, which you may see when you've finished classifying (click on the SDSS link). On the other hand, a trio of radio sources, more or less in a line, with the central one coinciding with a bright IR source, well that's likely to be a triple, the central engine (a supermassive black hole and its accretion disk) shooting out jets in opposite directions ... jets which terminate as bright radio sources, where the electrons slam into the diffuse gas of the intergalactic medium.

    Hope this helps. Happy hunting! 😃

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  • ivywong by ivywong scientist, admin

    Thanks JeanTate for the succinct explanation. Yes, the IR emission comes from the stars in the galaxy so in the event that the galaxy is not having too many supernovas and only have an active central supermassive blackhole, the radio emission will be confined to the centre of that galaxy.

    So it is very useful to click the "Discuss" button when you see any "interesting-looking" sources, and then have a look at what the SDSS survey sees in the optical. Note that SDSS will only be helpful for galaxies in the nearby Universe but it's worth having a look...

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