Blue spirals, major merger and an artifact (?)

I wanted to include the full image but did not know how to do it. Cutout brings out only a part of the image. So here is the link

Two stunning blue spirals at the bottom (z=0.004) and a busy 4-way merger (z=0.02) at the top.

Is that purple patch of light, below the bright star on the left, an artifact?




In our next data release (DECaLS DR5) we should have deeper multi-color imaging for these galaxies.

Yes, that purple flare is from the bright star. I suspect the straight top edge of the flare is the edge of one image.


When is DR5 expected?


DR5 will probably be released by mid-September.

I now have many many hours of searching Brown Dwarfs in W1/W2 (NEO2) for the Zooniverse project Backyard Worlds:P9, and have found a lot of good candidates :smile:

So PLEASE keep the brilliant and genius WISE W1/W2 layers in!!!


Definitely, the WISE layers are here to stay!

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(Post must be at least 20 characters, ok done)

Hmm looks like one of the two unWISE is removed? Only unWISE W1/W2 NEO2 right now…

The one called “Neo2” is actually a coadd of all the available data, up to and including NEO2 – so for static sky, it looks the same as the original, but deeper. Moving objects would be blurred out (more). We still have the original data around, I just didn’t want to clutter the viewer with too many layers…


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Oh that’s a real pity. For a long time this was actually the only way of quickly checking for movement when searching for brown dwarfs, a very important distinction for the Zooniverse project Backyard Worlds.

Luckily one of the volunteers built a page where this is also possible, but there is nothing as quick and clear as finding a candidate in DECaLS viewer and simply flipping between the two layers to check for movement :confused:

If that other page would be closed there would actually be no way for volunteers to check for movement anymore.

For your reference, check out the difference between the previous two WISE layers of this known nearby brown dwarf:



Thanks for your note – I didn’t realize it was being used in this way. I just turned back on the original unWISE W1/W2 layer. But really, we should be able to do much better – the “unWISE W1/W2” averages the first year of observations, and then “unWISE W1/W2 NEO2” layer averages the first year PLUS the two post-reactivation years (with the three year deactivation gap in between) – in the awesome example you sent, you can see how smeared out it is in the NEO2 image. Thing is, we also have one-coadd-per-six-months images – so a 7-frame movie over a lot of the sky. It would be fun to be able to show those!


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Very nice! Ofcourse I showed a prime example which can be considered ‘low hanging fruit’, but the same principle applies to the fainter ones that are further away.

The method you describe sounds pretty much like the method used in the Zooniverse project Backyard Worlds: Planet 9 to create the 4-frame flipbooks used as primary method to search for (moving) brown dwarfs and planet 9.

The example brown dwarf is actually the reason I started to freestyle search in DECaLS instead of using the project’s flipbooks. I’d say it’s obvious why :wink: Best guess now is I’ve already got quite a bit of candidate brown dwarfs in already.

At the moment the BYW team is already thinking about the best ways to incorporate new WISE data yet to come which will show movement even better since ofcourse more time has passed between images.

Thank you so much!

PS. there is no such thing as ‘too much layers’ in my world :wink:

Nice work with the flip mode (arrows) between surveys! Also access to DR5 it seems, great deep coverage in comparison to DR3 at first glance! So DR5 not officially released yet?

Maybe you noticed – if you hit the space bar it’ll flip back to the previous layer you had selected. Handy for blinking between two layers.

DR5 is not quite officially released. Probably ready in a couple of weeks.


Flipping awesome!

Where do the Decaps images come from btw? Couldn’t find out which survey is used.

DECaPS is the DECam Plane Survey, led by Eddie Schlafly, and just about to be released. Those images are absolutely stunning.


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Hi karthik,
You could change the size of the cutout by adding width and height parameters to the link :
example for the full group merger