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The mass of the missing baryons in the X-ray forest of the warm–hot intergalactic medium

Nature volume 433, pages 495–498 (2005)Cite this article

Abstract

Recent cosmological measurements indicate that baryons comprise about four per cent of the total mass-energy density of the Universe1,2, which is in accord with the predictions arising from studies of the production of the lightest elements3. It is also in agreement with the actual number of baryons detected at early times (redshifts z > 2)4,5. Close to our own epoch (z < 2), however, the number of baryons detected add up to just over half (∼ 55 per cent) of the number seen at z > 2 (refs 6–11), meaning that about ∼45 per cent are ‘missing’. Here we report a determination of the mass-density of a previously undetected population of baryons, in the warm–hot phase of the intergalactic medium. We show that this mass density is consistent, within the uncertainties, with the mass density of the missing baryons.

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Figure 1: The WHIM absorption in the Chandra LETG spectrum of Mkn 421.
Figure 2: The ‘missing’ baryons have been found in the WHIM.

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Acknowledgements

This work has been supported in part by NASA-Chandra and NASA-LTSA grants.

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Authors and Affiliations

  1. Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Massachusetts, 02138, Cambridge, USA

    Fabrizio Nicastro, Martin Elvis, Jeremy Drake, Antonella Fruscione, Yair Krongold & Andreas Zezas

  2. Astronomy Department, The Ohio State University, Columbus, Ohio, 43210, USA

    Smita Mathur & Rik Williams

  3. University of California-Berkeley, Berkeley, California, 94720, USA

    Taotao Fang

  4. Istituto de Astronomia, UNAM, DF 04510, Mexico City, Mexico

    Yair Krongold

  5. Massachusetts Institute of Technology, Massachusetts, 02139, Cambridge, USA

    Herman Marshall

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Correspondence to Fabrizio Nicastro.

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Supplementary information

Supplementary Methods

(a) Observations. (b) Data Reduction and Analysis. (c) Comparison of Data with Models. (DOC 49 kb)

Supplementary Discussion

(a) Line Identification: ruling out blazar outflows. (b) Metallicity dependency on modeling. (DOC 44 kb)

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Nicastro, F., Mathur, S., Elvis, M. et al. The mass of the missing baryons in the X-ray forest of the warm–hot intergalactic medium. Nature 433, 495–498 (2005). https://doi.org/10.1038/nature03245

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