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Observations of galaxies and galaxy clusters in the local universe can account for only ∼10% of the total baryon content. Cosmological simulations predict that the “missing baryons” are spread throughout filamentary structures in the cosmic web, forming a low-density gas with temperatures of 105−107 K. We search for this warm-hot intergalactic medium (WHIM) by stacking the Planck Compton y-parameter map of the thermal Sunyaev-Zel’dovich (tSZ) effect for 1 002 334 pairs of CMASS galaxies from the Sloan Digital Sky Survey. We model the contribution from the galaxy halo pairs assuming spherical symmetry, finding a residual tSZ signal at the 2.9σ level from a stacked filament of length 10.5 h−1 Mpc with a Compton parameter magnitude y = (0.6 ± 0.2)×10−8. We consider possible sources of contamination and conclude that bound gas in haloes may contribute only up to 20% of the measured filamentary signal. To estimate the filament gas properties we measure the gravitational lensing signal for the same sample of galaxy pairs; in combination with the tSZ signal, this yields an inferred gas density of ρb = (5.5 ± 2.9) × ρ̄b with a temperature T = (2.7 ± 1.7) × 106 K. This result is consistent with the predicted WHIM properties, and overall the filamentary gas can account for 11 ± 7% of the total baryon content of the Universe. We also see evidence that the gas filament extends beyond the galaxy pair. Averaging over this longer baseline boosts the significance of the tSZ signal and increases the associated baryon content to 28 ± 12% of the global value.
© ESO 2019
© ESO 2019
|Number of pages||12|
|Journal||Astronomy & Astrophysics|
|Early online date||5 Apr 2019|
|Publication status||E-pub ahead of print - 5 Apr 2019|
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- 1 Finished
GLOBE: Global Lensing Observations to go Beyond Einstein (027451/1)
1/11/15 → 31/10/21
- School of Physics and Astronomy - Reader
Person: Academic: Research Active (Research Assistant)
- School of Physics and Astronomy - PROFESSOR
Person: Academic: Research Active