This projection shows the sky distribution of 2RXS sources
in Galactic coordinates. The size of each dot scales with the source
count rate (brightness) and the colour represents the X-ray colour.
Image credit: © MPE.
Scientists at the Max Planck Institute for Extraterrestrial Physics (MPE) have revisited the all-sky survey carried out by the ROSAT satellite, to create a new image of the sky in at X-ray wavelengths. Along with this a revised and extended version of the catalogue of bright and faint point-like sources will be released. The now published “2RXS catalogue” provides the deepest and cleanest X-ray all-sky survey to date, which will only be superseded with the launch of the next generation X-ray survey satellite, eROSITA, currently being completed at MPE.
In the 1990s, the ROSAT X-ray satellite performed the first deep all-sky survey with an imaging telescope in the 0.1-2.4 keV energy band, increasing the number of known X-ray sources by a factor of approximately 100. The intention of the new analysis was to improve the reliability of the catalogue, by re-analysing the original photon event files, using an advanced detection algorithm and a complete screening process.
Scientists at the Max Planck Institute for Extraterrestrial Physics (MPE) have revisited the all-sky survey carried out by the ROSAT satellite, to create a new image of the sky in at X-ray wavelengths. Along with this a revised and extended version of the catalogue of bright and faint point-like sources will be released. The now published “2RXS catalogue” provides the deepest and cleanest X-ray all-sky survey to date, which will only be superseded with the launch of the next generation X-ray survey satellite, eROSITA, currently being completed at MPE.
In the 1990s, the ROSAT X-ray satellite performed the first deep all-sky survey with an imaging telescope in the 0.1-2.4 keV energy band, increasing the number of known X-ray sources by a factor of approximately 100. The intention of the new analysis was to improve the reliability of the catalogue, by re-analysing the original photon event files, using an advanced detection algorithm and a complete screening process.
An important feature of the new catalogue is a statistical
assessment of the reliability of the sources. Because of the extreme
sensitivity and low background of the ROSAT PSPC instrument, cosmic
X-ray sources can be identified with the detection of just a few
photons. These are sometimes difficult to distinguish from random
fluctuations, and the new catalogue provides an assessment of this
effect, based on simulated data.
An
artist’s impression of ROSAT, a satellite X-ray telescope launched 1
June 1990, on what was initially designed as an 18-month mission. ROSAT
actually operated until 12 February 1999 and re-entered the Earth’s
atmosphere on 23 October 2011. Image credit: DLR.
The
catalogue contains more than just a list of sources, for example X-ray
images and overlaid X-ray contour lines for each of the detections are
provided. For many sources, X-ray light curves were created to shows how
the sources vary in brightness on intra-day timescales. For the
brightest sources X-ray spectral fits were performed based on three
basic spectral models, a power law, a thermal-plasma and a black-body
emission model. This is important because it can distinguish what kind
of cosmic source produces the X-rays. These include powerful accreting
black holes, giant clusters of galaxies, active stars and the remnants
of stars that exploded in supernova explosions.
With
the new catalogue, the astrophysical community will now be able to
explore these objects in the X-ray sky with more confidence, and with
considerably more information.
Additionally,
the experience gained by the high-energy group at MPE in creating the
new ROSAT all-sky survey X-ray source catalogue will be integrated in
the data reduction analysis and scientific exploration of the
forthcoming eROSITA all-sky survey. The eROSITA X-ray survey telescope
currently built by MPE will be launched in 2017 to scan the whole sky
with even higher precision than ROSAT, reaching 30 times deeper into the
universe. One of its main goals is to measure the distribution of about
100,000 galaxy clusters, containing thousands of galaxies each. The
2RXS catalogue is the deepest and most reliable X-ray all-sky survey
before eROSITA.
