Skip to main content

Research Repository

Advanced Search

Warm-hot baryons comprise 5-10 per cent of filaments in the cosmic web

Eckert, D.; Jauzac, M.; Shan, H.; Kneib, J.-P.; Erben, T.; Israel, H.; Jullo, E.; Klein, M.; Massey, R.; Richard, J.; Tchernin, C.

Warm-hot baryons comprise 5-10 per cent of filaments in the cosmic web Thumbnail


D. Eckert

H. Shan

J.-P. Kneib

T. Erben

H. Israel

E. Jullo

M. Klein

J. Richard

C. Tchernin


Observations of the cosmic microwave background indicate that baryons account for 5 per cent of the Universe’s total energy content1. In the local Universe, the census of all observed baryons falls short of this estimate by a factor of two2, 3. Cosmological simulations indicate that the missing baryons have not condensed into virialized haloes, but reside throughout the filaments of the cosmic web (where matter density is larger than average) as a low-density plasma at temperatures of 105−107 kelvin, known as the warm–hot intergalactic medium3, 4, 5, 6. There have been previous claims of the detection of warm–hot baryons along the line of sight to distant blazars7, 8, 9, 10 and of hot gas between interacting clusters11, 12, 13, 14. These observations were, however, unable to trace the large-scale filamentary structure, or to estimate the total amount of warm–hot baryons in a representative volume of the Universe. Here we report X-ray observations of filamentary structures of gas at 107 kelvin associated with the galaxy cluster Abell 2744. Previous observations of this cluster15 were unable to resolve and remove coincidental X-ray point sources. After subtracting these, we find hot gas structures that are coherent over scales of 8 megaparsecs. The filaments coincide with over-densities of galaxies and dark matter, with 5–10 per cent of their mass in baryonic gas. This gas has been heated up by the cluster’s gravitational pull and is now feeding its core. Our findings strengthen evidence for a picture of the Universe in which a large fraction of the missing baryons reside in the filaments of the cosmic web.


Eckert, D., Jauzac, M., Shan, H., Kneib, J., Erben, T., Israel, H., …Tchernin, C. (2015). Warm-hot baryons comprise 5-10 per cent of filaments in the cosmic web. Nature, 528, 105-107.

Journal Article Type Article
Acceptance Date Oct 1, 2015
Online Publication Date Dec 2, 2015
Publication Date Dec 3, 2015
Deposit Date Apr 5, 2016
Publicly Available Date May 3, 2016
Journal Nature
Print ISSN 0028-0836
Electronic ISSN 1476-4687
Publisher Nature Research
Peer Reviewed Peer Reviewed
Volume 528
Pages 105-107


You might also like

Downloadable Citations