WISE data in ls_dr10.tractor table

[Dong-Woo Kim]

Hi, 

The dr10 tractor table (got from the Data Lab) contains WISE W1-W4 information for most objects. This is great, but I wonder where the W1-W4 data are from. In one field, ra = 215.82190 - 219.931070  and dec = 32.239620 - 35.87510, there are 787K dr10 objects. More than 60% of them have W1 with snr_w1 > 3. However, if I cross-match with CATWISE2020 or unWISE objects, I get only 30% or 40% within separation < 1 or 3".  Where are those W1-W4 in tractor coming from if they differ from unWISE/CATWISE? Is there a way to connect dr10 objects to unWISE/CATWISE sources? unWISE/CATWISE do not have W3 and W4. Are they from AllWISE?  

Thanks in advance.    - dw

[Dustin Lang]

Hi,

In the Legacy Surveys data reductions, we did "forced photometry" on the WISE images.  That is, we take the DR10 optical detected objects and photometer those locations in the WISE images, using the same point source or galaxy shapes as  we determined from the optical images.

The W1/W2 images come from the 7-year unWISE coadds from Meisner+.  The W3/W4 come from the original unWISE coadds from Lang.

The NOIRLab DataLab has strong cross-match capabilities.  I'm not sure if they have the Unwise Catalog or CatWISE catalogs loaded, though.

cheers,

dustin

--
You received this message because you are subscribed to the Google Groups "DECam Legacy Survey" group.
To unsubscribe from this group and stop receiving emails from it, send an email to decam-legacy-su...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/decam-legacy-survey/2805ef79-ecd8-4274-accf-f32fe8d234c2n%40googlegroups.com.

[Dong-Woo Kim]

Hi Dustin,

 

Very glad to hear your prompt response.  If the Legacy team performed its own photometry in W1-W4 bands, is there any info about the comparison with the unWISE catalog? Any comment on CATWISE?  As an end user, it is a bit confusing.

 

BTW, the NoirLab provides both unWISE and CATWISE catalogs in their DB as well as the match tables, called x1p5 (nearest within 1.5”) between all pairs of catalogs.

 

Cheers,

dw

Dong-Woo Kim

(HEAD, CXC)

Center for Astrophysics | Harvard & Smithsonian

Office: (617) 496 7852 | Cell: (617) 413 7457

60 Garden Street | MS 6 | Cambridge, MA 02138

cfa.harvard.edu | Facebook | Twitter | YouTube | Newsletter

[Dustin Lang]

Hi Dong-Woo,

Thanks for your comments, I agree there are a lot of WISE photometry products around!  We have not done any of those comparisons, but it's a very good idea.

cheers,

dustin