Likelihood Analysis: Data Access Using SLAC's Astro Server

SLAC's e Fermi LAT Data Portal's Astro Server allows you to efficiently do region of the sky searches based on time, region of interest, energy and class level. This server is similar to the FT1 skimmer, but is much more efficient for the searches it supports. See: Comparison: Merit Skimmer, Fits Skimmer, and Astro Server.

The Astro Server's "Request" GUI enables you to select from multiple "Event Samples" (e.g., P6_public_v2), and you can select the event data based on any combination of:

  • Energy Range
  • Position in sky (ra, dec, radius)

Note: Position can be looked up in SIMBAD catalog.

  • Event Class (transient, source, diffuse) – See: Introduction to the Standard Analysis of LAT Data: Photon Classification.
  • Time Range (MET)

You can also select any, or all, of the following outputs:

Web Interface: Astro Server

From the Data Portal, click on the Astro Server tab. The Astro Server Request GUI will be displayed:

Notes:

  • Caution: Maximum energy is required by the likelihood tool, so if you do not specify it here, you will have to postprocess the Astro Server's output file using gtselect, which requires maximum energy to be specified, before running the likelihood.
  • Enter position or source; you don't need both. If you do enter both, source overrides position.
  • Warning! Expert options are intended for expert users (normally developers) only in that they allow you to apply cuts that may make the response functions invalid.
  • At the time this was written, the Astro Server failed if the job name contained a space.

Example: e-mail notification

Dear chuckp,
Job likelihood_tutorials has finished. Results are in:

/nfs/farm/g/glast/u27/DataServer/1289948152642

You can reach your data via ftp:

ftp://ftp-glast.slac.stanford.edu/glast.u27/DataServer/1289948152642

Please use: tonyj@slac.stanford.edu or reply to this e-mail with any concerns/suggestions.
You are also encouraged to file a bug/improvement request in Jira.

Sincerely Yours,
DataPortal server

Tip: ftp-glast.slac.stanford.edu/glast.u27/DataServer/your_jobNumber
equates to: /nfs/farm/g/glast/u27/DataServer/your_jobNumber.

Retrieve the Data

Caution! Take care to download or copy your own data;
these files can be quite large.

Depending on your work environment, you can retrieve the data by either:

  1. Clicking on the ftp link included in the email.

A page similar to the following will be displayed:

  1. Download the data by:

Clicking on the ftp links of the files you wish to download.

   OR

Copying the files using the equivalent path to the DataServer shown above.

For example, from your work directory on SLAC Central Linux, you could enter the following command:

cp /nfs/farm/g/glast/u27/DataServer/yourJobNumber/*.* .

Last updated by: Chuck Patterson 11/15/2010