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Find data for quasars

Back to Quasars/Cosmology index

Search for quasars (open tool in new window)

  1. Go to the Spectroscopic Query Form (link opens in new window). From the astronomers' main page, look under Search Tools.

  2. In the Limit number of output rows textbox, enter the number of quasars you would like the search to return. If you want unlimited number of rows returned, enter 0.

  3. In the Output Format textbox, enter the format you want for your output. HTML will output results as a table in your browser. CSV output can be read by many graphing programs.

  4. In the Parameters section, select what types of Spectroscopy and Imaging data you would like returned. Typical returns the most common parameters, including the redshift (z) and the r magnitude. You can select any parameters from the menu. To select more than one, hold down CTRL while clicking on each one.

  5. You can use the Filters checkboxes to choose which filter names to return. The form will return only the names of the filters, not the images. You can then use the filter names as part of a query to the Science Archive Server (SAS) (link opens in new window).

  6. Skip the Position Constraints options for now, so you can specify that you want only quasars. Under Spectroscopy Constraints, select both QSO and HIZ_QSO. This will ensure that the tool will only return results for quasars.

  7. If you want to specify a redshift range, enter it in the min and max boxes of redshift.

  8. If you want to specify a range of redshift confidence, enter it in the min and max boxes of confidence. Confidence is a number between 0 and 1; it is usually a good idea to limit spectroscopic searches to objects with a redshift confidence greater than 0.35.

  9. If you want to specify quasars that were targeted in any specific way, select them from the Target Flags menu. See the guide How do I find out if SDSS's imaging data for an object are reliable? to learn how to interpret flags.

  10. Read on to learn how to specify other constraints, or click Submit Request to send your search to the database.

  11. You will see your results in a new window.

You can also apply more constraints to your search, searching for positions or magnitudes. You can use an SQL search (new window) to request other constraints, to give you any type of quasar sample that you want. See the SQL Tutorial for more on how to use SQL.

Next: Search by position

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