How faint can an IR source be ...
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JeanTate
... before you decide that it's just noise?
In this case, I think there's actually an IR source, but I also think it's close to the 'noise threshold'.
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enno.middelberg
scientist, translator
Good question. Normally one would define a threshold below which sources are considered noise. In the case you give here I'd be willing to bet (a little) money that there is a IR source coincident with the radio object. I've dug up the coordinates and fed them into the WISE image cutout service which gave me not only a b/w image of the image you see (WISE band 1) here but also an image in another band (WISE band 2). And guess what - the other image also has a faint speck in it at the same location, which has been marked there with a blue circle. It's unlikely to have two "noise" specks at the same location in different bands (=different detectors), so the IR is real.
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JeanTate
in response to enno.middelberg's comment.
Thanks!
When classifying, do you suggest we use our own - individual - judgement? Or maybe add something in the tutorial?
When the zooite classifications are all in, you can of course 'run the ruler' over the data, and - hopefully! - get a nice smooth flux threshold/detection vs 'IDed as IR source' fraction, and use that to calibrate and analyze all our clicks! 😃
I've dug up the coordinates
Is there a way we ordinary zooites can do this?
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enno.middelberg
scientist, translator
in response to JeanTate's comment.
When doing this automagically one takes the conservative approach and sets a somewhat higher threshold - as the saying goes "bad data is worse than no data", so we'd rather ignore a few true sources than to have the final catalog polluted with noise. However, when a human does this one can accepts a little fainter IR sources. And yes, use your individual judgement! You'll most likely get it right.
Re the coordinates: apparently work is underway to display the coordinates and survey from which the data were taken. Until that is done it's a bit cumbersome: use https://api.zooniverse.org/projects/radio/subjects/ARG0001sgo (change the source ID at the end) and you'll get a data base dump for that source. Then copy & paste the coordinates into, e.g., the FIRST image cutout tool (here the source name indicates that it is a FIRST source) at http://third.ucllnl.org/cgi-bin/firstcutout for a GIF/FITS image of the radio and into the WISE cutout tool at http://irsa.ipac.caltech.edu/applications/wise/ for an overview of the 4 WISE band images. This can be very helpful at times, in particular when parts of a radio source are outside an image.
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