FAQ
FAQ
Q: The image is too large in my browser, can I change this?
A: Try shrinking your browser window width, this can help with the sizes of the different items on the page.
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Q: I'm not sure if a galaxy actually contains shells or not. What should I do?
A: Select "Yes" when asked if the galaxy contains shells, and draw where think you see any shell structures. If multiple volunteers agree, it's probably a real feature.
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Q: The shell is very faint, should I mark it?
A: Yes, if you can see a coherent shape, even faintly. Euclid and DESI have very deep imaging, and faint structures are often scientifically important.
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Q: Do I have to mark every feature on the image?
A: No, only mark features that look like shells. Features that contain gas-like structure or are pointing towards the center of the galaxy are probably not shells.
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Q: Should I flag stars or artifacts if they confuse the image?
A: No - just do your best to ignore them. Bright foreground stars, cosmic rays, and image artifacts are common. Unless they truly hide the entire image, continue with the classification on the parts you can see.
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Q: How do I tell the difference between a shell and a tidal stream?
A: The path of a tidal stream will usually vary how far away it is from the center of the host galaxy, sometimes being farther away and sometimes being closer to the central galaxy. Shells will generally be oriented perpendicular to the center of the host galaxy at roughly the same distance. Tidal streams and shells can often be found in the same galaxies, so it's okay to mark some features but not others!
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Q: How do I tell the difference between a shell and spiral arms or other central features?
A: Shells are usually redder than the central galaxy, appearing brown, orange, or yellow in DESI and Euclid images. This is because they are composed of old, red stars from dwarf galaxies. Spiral arms and other central star-forming/gas clumps are usually blue in appearance because younger stars are more blue on average.
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Q: How can I tell the difference between an Einstein ring and a shell?
A: Einstein rings will usually have some structure within them, and are not very large. It's also common for there to be several Einstein rings in the same image, which should all look roughly the same color and size. Shells can vary in size and will usually span much larger angles around the galaxy than an Einstein ring.