DESI cone search has a minimum search radius. Bug?

Question

Selection deleted

SELECT targetid, mean_fiber_ra, mean_fiber_dec, desiname, spectype, subtype, survey, z, zerr, zwarn, zcat_primary, zcat_nspec
    FROM desi_dr1.zpix
    WHERE q3c_radial_query(mean_fiber_ra,mean_fiber_dec,0.000000,0.000000,0.000167)
    
The above query is for a 6'' radius cone search in DESI. It returns 3705 entries. In my limited testing it seems to return all entries within at least 0.3'. q3c_radial_query works fine for tables form other surveys. Seems to be a bug in the SQL side of things. The Python API can reproduce this error with this input query string.

Is this intended?

Answer 1

Hi Sunil,

Thanks taking the time to pose your question, and apologies about the delay in responding. So the value 0.000167 *3600 = 0.6 arcsec (and not 6 arcsec) but there is another issue in that it seems some mean_fiber_ra and dec values are just set exactly to zero. I will check with the DESI team is this is expected. Have you tried using other non-zero coordinates? One informative test would be to add the distance as an output (example below) so you can verify that the values are correct. Please let us know whether this solves your question or if you encounter more issues.

`q3c_dist(ra1, dec1, ra2, dec2) as dist` as part of your query for the distance in degrees, or you can add `q3c_dist(mean_fiber_ra,mean_fiber_dec,0.100000,-0.100000)*3600.0 as dist_arcsec` for the arcsec version.