Tracing missing baryons in the cosmic filaments with tSZ and CMB-lensing stacking

Abstract We investigate the distribution of missing baryons in the cosmic filaments by stacking ∼ 30,700 filaments across the northern and southern SDSS sky regions using Planck Compton- y and CMB lensing maps. Filaments are identified using the DisPerSE algorithm applied to the SDSS LOWZ-CMASS galaxy samples, selecting structures with lengths between 30–100 cMpc and redshifts in the range 0.2 < z < 0.6. Radial profiles are extracted out to 25 cMpc from the filament spines, and galaxy clusters with halo masses above ∼ 3 × 10 13 M ⊙ are masked to reduce contamination. We detect the thermal Sunyaev-Zel'dovich (tSZ) signal at 7.82σ and the CMB lensing signal at 7.78σ. The stacked profiles are corrected by a geometric bias correction based on filament inclination with respect to the line-of-sight, and they are portrayed assuming isothermal, cylindrically symmetric models. We explore different gas and matter density distributions, focusing on the β -models with ( α,β ) = (2,2/3) or (1,1). By jointly fitting the Compton- y and κ profiles, we constrain the central electron overdensity and temperature to be δ = 4.18 +2.01 -1.06 and T e = 2.74 +0.65 -0.53 × 10 6 K for the standard β -model. These results suggest that filamentary WHIM in our selected long filaments contributes a significant baryon fraction of 0.127 +0.019 -0.021 × Ω b to the cosmic baryon budget.