Vol. 624
In section 3. Cosmology

Probing the missing baryons with the Sunyaev-Zel’dovich effect from filaments

by A. de Graaff, Y.-C. Cai, C. Heymans, and J. A. Peacock 2019, A&A, 624, A48

Cosmological simulations predict that the majority of missing baryons in the Universe form a diffuse warm-hot gas in filaments in the cosmic web. In this work, the authors searched for these gas filaments by stacking the Planck Compton y-parameter map of the thermal Sunyaev-Zel’dovich effect for 1,002,334 pairs of CMASS galaxies from the Sloan Digital Sky Survey, assuming that the line connecting neighbouring massive galaxies is a proxy for the location of filaments. Significant SZ signal for the stacked galaxy pairs was found. After identification and removal of potential sources of contamination to the residual signal, the authors estimated the filament gas properties - in other words, a filament gas density rho_b = (5.5+-2.9)xrhomed_b and temperature T=(2.7+-1.7)x10^6 K that is consistent with predictions from hydrodynamical simulations. Considering the total volume spanned by the CMASS galaxies, this new measurement can account for 11 +-7% of the total baryon content of the Universe. Evidence was also found that filaments extend beyond the galaxy pairs: including the contribution of this extended filament region may account for 28 +- 12% of the total baryon content.