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 Spectroscopic Query Form .
  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. Select minimal under "Spectroscopy Parameters" in the "Parameters to Return" section. This will return the MJD, plate, and fiberID that you will need to actually get the spectra from the Science Archive Server.
  4. Under Position Constraints, make sure None (No Position Constraint) is selected.
  5. Under Imaging Constraints, look for the row of textboxes labeled "Colors."
  6. Enter 0.4 in the max u-g textbox.
  7. Enter -0.15 in the min g-r textbox.
  8. Unselect Extended Sources and make sure Point Sources is selected in the "Obj Type" section of the form.
  9. Verify that nothing else is selected.
  10. Click on Submit Request. Depending on database load, this query takes about half a minute to run.
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Getting the actual spectra for the objects

  1. Select CSV output and save the .csv file to disk.
  2. Go to the SAS optical bulk spectrum search .
  3. Upload the csv file, or copy and paste the csv contents into the form.
  4. Click on Search.
  5. Download the FITS file by clicking the Download (rsync) or Download (wget) buttons.
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