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eROSITA Archive: Getting Started

General

The eROSITA archive contains calibrated event files.

These event files contain the information generated by the cameras used during the Cal-PV observations and are created by the eROSITA Science Analysis Software System (eSASS) pipeline after the received telemetry data from eROSITA of each observation has been re-formated, packaged, and archived by a pre-processor. Note that not all Cal-PV observations have been performed with all 7 eROSITA telescope modules and that only one event calibrated event list per observed field is released.

More specifically, the release calibrated event list of each Cal-PV observation contain photons:

  • with energies between 0.2 - 10 keV;
  • flagged as flag=0xC000F000, i.e. good events from the nominal field of view, excluding bad pixels (click here for further information about flags);
  • with patterns pattern=15, i.e. including single, double, triple and quadruple events (access here to learn more about pattern fractions).
The general structure of the calibrated event files is described under eSASS products description in the Event file description section and its naming scheme is described in the Pipeline data product's file naming scheme section of the MPE eROSITAS SASS website. Use the eSASS tasks to obtain individual camera event lists and to analyse the data (see Cookbook and eSASS task descriptionse.

For practical purposes, the eROSITA-DE team has divided the Cal-PV observations into four categories:

  • Survey fields: these are scan observations of large, contiguous areas of the sky.
  • Magellanic Clouds: these are observations around the Small and Large Magellanic Clouds.
  • Galactic fields: these include observations with |Galactic latitude| < 17 deg.
  • Extragalactic fields: these include observations with |Galactic latitude| > 17 deg.
Choosing a threshold of Galactic nH = 1x1021 leads the same classification of the Galactic and extragalactic fields.

Archive access : Web, wget or download script

All the EDR data can be retrieved using the links in the archive page. From the HEASARC eROSITA EDR FTP archive, the /obs directory contains the calibrated event files for the different Cal-PV fields. Each observation comes with a validation report, which contains information about the target: coordinates, exposure time, used telescope modules, processing mode, type of observation, notes on observation features, etc. Users are strongly encouraged to read these reports and the corresponding documentation on this site before using the data. The /catalog directory contains FITS tables providing processed output from the detected sources in the field.

Additionally, the eROSITA archive can be accessed using the web interfaces Browse, wget, or with a download script.

  • Access via Web : The archive access via the Web makes use of database table to search for the science data. There are 4 available database tables associated with the eROSITA data, which are compiled and described at the eROSITA Browse link. These tables provide high-level information eROSITA sources. This table can be queried for position and several other parameters, and from the result page it is possible to select and retrieve the data files.

  • Wget : If you have wget installed, and the filename is already known, the data can be retrieved via 'wget'. For example using the HTTP protocol, if the user wants to retrieve the eFEDS main field 'eFEDs.tar.gz', they can retrieve this file (see Example) using 'wget'. 
    Example

   wget -q -nH --cut-dirs=5 -r -l0 -c -N -np -R 'index*' -erobots=off --retr-symlinks \
    
 https://heasarc.gsfc.nasa.gov/FTP/srg/data/erosita/edr/obs/eFEDS.tar.gz
  • download_wget: download_wget is a PERL script that uses the wget protocol, similarly to the example above, but simplifies the command and allows for more flexiblity. You can retrieve the download_wget and place it in your local machine 
     
Example: To download a specific sequence type: 
     
  > download_wget.pl https://heasarc.gsfc.nasa.gov/FTP/srg/data/erosita/edr/obs/eFEDS.tar.gz


To get help type :  > download_wget.pl help