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