unWISE W1/W2 NEO6 vs. Legacy Surveys DR9

The unWISE images show the entire sky while the Legacy Surveys seem to avoid the galactic plane. Why is this? Is the Milky Way too bright?


The Legacy Surveys were taken to select galaxies for follow-up with the DESI instrument (desi.lbl.gov). Since DESI is interested in the extragalactic sky (outside the Mliky Way), we avoid the Galactic plane, because of, yes, the very high star density, and also the large amount of dust that makes everything outside the galaxy fainter and redder.

For an extreme idea of what it would look like, check out the DECaPS layer, which uses the same DECam camera we used for the Legacy Surveys in the south, but observing the galactic center and plane:

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Awesome. Thanks for the answer.
That is a BUNCH of red/dust/many many stars/noise in that image! (It’s a cool image - but yikes! Ain’t no galaxies I can see!)

Where is this DECam camera located?

Cerro Tololo Inter-American Observatory in Chile, on the 4-meter Victor Blanco telescope.

As I look at the DECaPS layer observing the galactic center and plane I’m hoping to see a faint galaxy beyond all the dust and stars - but nope, I can’t find one. Have galaxies been imaged through the galactic rings and center? If so, where are they and where can I see them? What information is gained from such galaxies observed through such noise? Thanks again!

I don’t know – a related thing is that when we observe distant quasars through foreground galaxies – spectroscopy of these ones lets you probe the outskirts of galaxies. In this case it might help you measure stuff about the galactic dust, but I don’t really know how interesting that is.

measuring quasars in the area around the andromeda galaxy was how we found these really huge, underdense hydrogen halos, one denser inner one and another less dense outer one. these halos are so large that ours has already merged with m31’s. I think they are something like 250-320kpc in diameter, if my memory is right