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Galaxies are distributed throughout the universe as a complex network of nodes connected by filaments, which are then separated by voids. This is known as the cosmic web.
The fibers are thought to contain nearly all of the ordinary (so-called baryon) matter in the universe as a diffuse hot gas. However, the signal emitted by this diffuse gas is weak to the point that, in reality, 40-50% of the baryons are not detected.
These missing baryons are hidden in the filamentous structure of the cosmic web.
Nabila Aghanim, researcher at the Institut d’Astrophysique Spatiale (CNRS / Université Paris-Saclay), and Hideki Tanimura, postdoctoral researcher, together with their colleagues, are trying to locate them. In fact, in a new study, they presented a statistical analysis that reveals, for the first time, X-ray emission from hot baryons in filaments.
The team used the spatial correlation between the position of the filaments and the associated X-ray emission to provide evidence for the presence of hot gas in the cosmic network and measure its temperature for the first time. The detection was based on the stacked X-ray signal, in the ROSAT2 survey data, from approximately 15,000 large-scale cosmic filaments identified in the SDSS3 galaxy survey.
These results confirm previous analyzes by the same research group, based on the indirect detection of hot gas in the cosmic network through its effect on the cosmic microwave background. This opens the way for more detailed studies, using better quality data, to test the evolution of gas in the filamentous structure of the cosmic network.
Journal reference:
- H. T Tanimura et al. First detection of X-ray emission stacked by cosmic network filaments, Astronomy & Astrophysics (2020). DOI: 10.1051 / 0004-6361 / 202038521
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