Color Constraints Tutorial

How do I find all Objects with Spectra that Satisfy a Given Set of Color Constraints and then Get the Spectra?

This query, in particular, finds spectra for all objects at the hot end of the WD cooling sequence. For a simple example, this list is defined as objects with g-r <-0.15 and u-g <0.4.  Normally, when querying based on filter or color magnitudes, you should also make sure all the appropriate photo QA flags are set properly (to indicate the object’s photometry is trustworthy), but in this case, since all these objects have spectra, we will assume they were targeted and allocated a fiber based on good photometric magnitudes, so we don’t bother to check the QA flags.

Finding the Objects

  1. Go to the Spectro Query Server .
  2. Select “html” as output format if you want to look at your query results in your browser, or “csv” to save them in a “comma-separated values” file which you can use to retrieve spectra from the Data Archive Server later
  3. At the first line, enter 0 to have your query return an unlimited number of output rows/objects.
  4. Select “minimal” under “Spectroscopy Parameters” under “Parameters to Return”. This will return the MJD, plate, and fiberID that you will need to actually get the spectra from the Science Archive Server.
  5. Select the Best radio button between the parameter listboxes.
  6. Under Position Constraints, make sure “No Position Constraint” is selected.
  7. Enter 0.4 in the “u-g max” box.
  8. Enter -0.15 in the “g-r max” box.
  9. Unselect “Extended Sources” and make sure “Point Sources” is selected in the “Object Type” section of the form.
  10. Verify that nothing else is selected.
  11. Click on “Submit Request”. Depending on database load, this query takes about half a minute to run.

Getting the actual spectra for the objects

  1. Select csv output and save the csv file to disk.
  2. Go to the SAS bulk spectroscopic data retrieval form.
  3. Copy and paste the csv contents into the form.
  4. Click on submit.
  5. Select the desired spectra and click “Download FITS files”