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Nachrichten, Termine, Experten
The German eROSITA consortium (eROSITA-DE), which also includes the University of Bonn and which is being led by the Max Planck Institute for Extraterrestrial Physics (MPE), has released its second major public dataset, the “eROSITA Data Release 2” (DR2). Built from the first three all-sky surveys done by the eROSITA telescope aboard the Spectrum-Roentgen-Gamma (SRG) mission, DR2 provides the most sensitive and comprehensive catalogue of the X-ray sky currently available to the public.
Spearheaded by the University of Bonn, the analysis of a massive galaxy cluster has shown that the theoretical models for how the Universe formed largely match the observations made, albeit with some interesting discrepancies in the finer details.
“By combining three all-sky surveys, DR2 provides a much more complete inventory of the X-ray sky and a robust foundation for statistical studies,” says Miriam E. Ramos-Ceja, Ground Segment manager of the eROSITA instrument and lead author of the DR2 publication.
Nearly two million sources
The main DR2 catalogue contains close to two million X-ray sources detected in the 0.2–2.3 kiloelectronvolt (keV) band across the western half of the sky. This includes more than 1.9 million point-like sources, primarily stars and actively accreting supermassive black holes, as well as around 64,000 extended sources such as galaxy clusters, nearby galaxies and supernova remnants. The number of detected sources has roughly doubled compared to the first data release (see https://www.uni-bonn.de/en/news/021-2024 for the press release covering this event).
Together, these two catalogues capture the diversity of the X-ray universe, from nearby stars to distant active galactic nuclei (AGNs) and massive galaxy clusters. Many sources have been newly identified in X-rays, while others can now be characterized much more precisely.
Observations confirm models—except for the finer details
For its contribution, the research group led by Professor Thomas Reiprich and Jakob Dietl from the Argelander Institute for Astronomy at the University of Bonn is focusing on assessing and analyzing one specific object in the sky, namely galaxy cluster A3266. “We’re observing a supermassive galaxy cluster and the process by which matter accretes along cosmic filaments,” Dietl reveals. “Our working group in Bonn led the analysis of—and was the first to measure—the faint X-ray emission in the outer reaches of this galaxy cluster.”
The overarching questions that the researchers are attempting to answer are what the large-scale distribution of matter looks like in the present Universe, how it came to be so and whether it tallies with theoretical models. In terms of cosmological timescales, large objects like galaxy clusters only emerged very recently. “Studying them can tell you a great deal about the whole formation process that went on in the past,” Dietl explains. This is why the researchers are investigating the thread-like connections (“filaments”) between structures like these, such as those close to the massive galaxy cluster A3266, and are comparing them to what the theory is predicting.
“One interesting thing we’ve found is that the gas we’re observing in the outer reaches of the galaxy cluster and in the filaments is a bit hotter and denser than expected and contains relatively little by way of heavy elements,” Dietl reports. In his view, these differences demonstrate that, although the theoretical models for how the Universe was formed essentially agree with the observations, drilling down into the details reveals inconsistencies with the predictions made by these models, which may help to refine them further.
Says Reiprich: “The spectacular images that eROSITA has taken of A3266 and our interpretation of the physics going on inside it are bringing us closer to our goal: a detailed understanding of the process that produces galaxies and galaxy clusters in the Universe.” The work of the research group from the University of Bonn has been funded by its Matter Transdisciplinary Research Area and its new Our Dynamic Universe Cluster of Excellence.
More information on eROSITA
eROSITA is the soft X-ray instrument aboard the Spektrum-RG (SRG), which is a joint Russian-German science mission supported by the Russian Federal Space Agency (Roscosmos) in the interests of the Russian Academy of Sciences, represented by its Space Research Institute (IKI), and the German Space Agency at the German Aerospace Center (DLR). The SRG spacecraft was built by the Lavochkin Association (NPOL) and its subcontractors and is operated by NPOL with support from the Max-Planck Institute for Extraterrestrial Physics (MPE).
The eROSITA telescope was launched into space on board the SRG mission on July 13, 2019. Its large collecting area and wide field of view are designed to perform a deep all-sky survey in the X-ray band. Over the course of six months (December 2019 to June 2020), SRG/eROSITA completed the first survey of the whole sky at energies of between 0.2 and 8 keV. This is significantly deeper than the only all-sky survey previously performed with an X-ray imaging telescope, which was done by the ROSAT X-ray observatory in 1990 at energies of between 0.1 and 2.4 keV. Three more scans of the entire sky were completed between June 2020 and February 2022.
eROSITA-DE is being led by the MPE and includes the Dr. Karl Remeis Observatory in Bamberg, Hamburg Observatory (the observatory of the University of Hamburg), the Leibniz Institute for Astrophysics Potsdam (AIP) and the Institute for Astronomy and Astrophysics at the University of Tübingen, with support provided by the DLR and the Max Planck Society. The University of Bonn’s Argelander Institute for Astronomy and Ludwig-Maximilians-Universität München are also involved in the scientific evaluation of eROSITA as associated institutions.
The eROSITA data is being processed using the eSASS software system developed by eROSITA-DE. eROSITA was put into safe mode in February 2022, since when it has not resumed its scientific operations.
Jakob Dietl
Argelander Institute for Astronomy
University of Bonn
Phone: +49 228 73-5770
Email: J.Dietl@uni-bonn.de
J. Dietl, A. Veronica, T. H. Reiprich, F. Pacaud, Y. Zhao, J. S. Sanders, B. Seidel, M. C. H. Yeung, K. Dolag and E. Gatuzz: “A study of the large-scale formation in the environment of A3266 Infalling Groups, Filaments, and a Pre-Merger Cold Front,” in: “Astronomy & Astrophysics.” DOI: 10.1051/0004-6361/202660862
advance copy via arXiv:
https://erosita.mpe.mpg.de/dr2/ DR2 Website
https://www.mpe.mpg.de/8215311/news20260731 press release MPE
https://arXive: https://arxiv.org/abs/2607.28140
The team from the Argelander Institute for Astronomy at the University of Bonn who assessed and anal ...
Source: Jakob Dietl/Uni Bonn
Copyright: Jakob Dietl/Uni Bonn
An X-ray image of galaxy cluster A3266: The massive galaxy cluster A3266 is shining brightly in the ...
Source: Jakob Dietl/Uni Bonn/eROSITA-DE
Copyright: Jakob Dietl/Uni Bonn/eROSITA-DE
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Journalists
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English
The team from the Argelander Institute for Astronomy at the University of Bonn who assessed and anal ...
Source: Jakob Dietl/Uni Bonn
Copyright: Jakob Dietl/Uni Bonn
An X-ray image of galaxy cluster A3266: The massive galaxy cluster A3266 is shining brightly in the ...
Source: Jakob Dietl/Uni Bonn/eROSITA-DE
Copyright: Jakob Dietl/Uni Bonn/eROSITA-DE
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