I want to run a query of the DESI DRR1 QSOAGN table, so that only sources with coordinates within the eROSITA public footprint are returned. The basic syntax is: SELECT TOP 100 * FROM desi_dr1.agnqso I want to get all sources in the eROSITA footprint

Question

I want to run a query of the DESI DRR1 QSOAGN table, so that only sources with coordinates within the eROSITA public footprint are returned

Answer 1

Hello,

it is likely very inefficient to request all sources in DESI DR1 that are within the eROSITA footprint. Unless you have very specific requirements to do so, may I suggest that you instead perform a cross-matching query for all sources of interest in the eROSITA survey (have a list of their IDs, RA, and Dec values, upload it as a table to your MyDB in Data Lab), within a desired search radius (usually in arcseconds). Then, retrieve those with matches in DESI DR1.

Examples of how to do crossmatches on Data Lab are in several of our Jupyter notebooks, for instance in this one:

https://github.com/astro-datalab/notebooks-latest/blob/master/04_HowTos/CrossmatchTables/How_to_crossmatch_tables.ipynb

You can also do cross-matches using our website, but with more restrictions on the number of rows for instance:

https://datalab.noirlab.edu/legacy/xmatch.php