This image shows half of the X-ray sky projected onto a circle (called the Zenit Equal Area projection) with the center of the Milky Way on the left and the galactic plane extending horizontally. The photons were color coded based on their energy (red for energies 0.3 to 0.6 keV, green for 0.6 to 1 keV, blue for 1 to 2.3 keV). Credit: MPE, J. Sanders for the eROSITA consortium
The German eROSITA consortium has released data from its part of the first survey of the sky carried out by the Soft X-ray Imaging Telescope flying aboard the Spectrum-RG (SRG) satellite. With approximately 900,000 distinct sources, the first eROSITA All-Sky Survey (eRASS1) resulted in the largest X-ray catalog ever published. The work is published in the journal Astronomy and astrophysics.
Alongside the data, the consortium published a series of scientific papers describing new results ranging from studies of planetary habitability to the discovery of the largest cosmic structures.
Based on the first six months of observations, eROSITA has already detected more sources than have been known in the 60-year history of X-ray astronomy. Now available to the global scientific community, this data will revolutionize our knowledge of the universe at high energies.
The eRASS1 observations with the eROSITA telescope were carried out from December 12, 2019 to June 11, 2020. In the most sensitive energy range of the eROSITA detectors (0.2-2 keV), the telescope detected 170 million X-ray photons, for which the cameras can accurately measure incoming energy and arrival time.
The catalog was then constructed, after careful processing and calibration, by detecting photon concentrations in the sky against a bright, diffuse, large-scale background. After eRASS1, eROSITA continued scanning the sky and accumulated several additional whole-sky surveys. This data will also be disseminated worldwide in the coming years.
The eRASS1 catalog covers half of the X-ray sky, the data sharing of the German eROSITA consortium. It consists of more than 900,000 sources, including some 710,000 supermassive black holes in distant galaxies (active galactic nuclei), 180,000 X-ray emitting stars in our own Milky Way and 12,000 galaxy clusters, as well as a small number of other exotic classes. from sources such as X-ray emitting binary stars, supernova remnants, pulsars and other objects.
“These are mind-blowing numbers for X-ray astronomy,” says Andrea Merloni, eROSITA principal investigator and first author of the eROSITA catalog article. “We detected more sources in six months than the large flagship missions XMM-Newton and Chandra did in nearly 25 years of activity.”
In coordination with this publication, the German eROSITA consortium submitted nearly 50 new scientific publications to journals, adding to the more than 200 already published by the team before the data was released.
Most of the new papers feature selected discoveries, including a giant filament of pristine hot gas stretching between two galaxies and two new “quasi-periodically erupting” black holes. Further studies of how X-ray irradiation from a star can affect the atmosphere and water retention of orbiting planets, as well as statistical analysis of flickering supermassive black holes.
“The scientific scope and impact of the investigation are quite impressive; it is difficult to express in a few words,” says Mara Salvato, who, as spokesperson for the German eROSITA consortium, coordinates the efforts of approximately 250 scientists organized into 12 working groups. “But the articles published by the team will speak for themselves.”
In these two images, a special image processing algorithm is used to separate extended features (left) from point sources (right). Credit: MPE, J. Sanders for the eROSITA consortium
This first eRASS data release (DR1) makes public not only the source catalog, but also X-ray sky images at multiple X-ray energies and even lists of individual photons with their positions in the sky, their energies and their precise arrival times.
The software required for eROSITA data analysis is also included in the release. For many source classes, additional data from other wavebands have also been incorporated into so-called “value-added” catalogs that go beyond purely radiographic information.
“We have made enormous efforts to release high-quality data and software,” added Miriam Ramos-Ceja, who leads the eROSITA operations team. “We hope this will expand the base of scientists around the world working with high-energy data and help push the frontiers of X-ray astronomy.”
“The eROSITA collaboration has done a remarkable job of publishing the data and publishing all these amazing new results at the same time,” says Kirpal Nandra, director of MPE. “There’s a lot more to come from us, and we can’t wait to see what the rest of the world does with public data.”
Avid eROSITA observers may know that the primary scientific goal that motivated the telescope was to constrain cosmological models using galaxy clusters. The cosmological results, based on an in-depth analysis of eRASS1 clusters, will be published in approximately two weeks.
More information:
A. Merloni et al, The SRG/eROSITA total sky study, Astronomy and astrophysics (2024). DOI: 10.1051/0004-6361/202347165
Provided by the Max Planck Society
Quote: First release of eROSITA celestial survey data makes public largest-ever catalog of high-energy cosmic sources (January 31, 2024), retrieved January 31, 2024 from
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