Tracing Missing Baryons in the Cosmic Filaments with tSZ and CMB-Lensing Stacking

Abstract: We investigate the distribution of missing baryons in cosmic filaments by stacking approximately 31,300 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 $3 \times 10^{13}$ solar masses are masked to reduce contamination. We detect the thermal Sunyaev-Zel'dovich (tSZ) signal at $7.82\sigma$ and the CMB lensing signal at $7.78\sigma$. The stacked profiles are corrected by a geometric bias related to filament inclination with respect to the line of sight, and modeled assuming isothermal, cylindrically symmetric gas distributions. We explore different gas and matter density distributions, focusing on $\beta$-models with $(\alpha, \beta) = (2, 2/3)$ or $(1, 1)$. By jointly fitting the Compton-$y$ and lensing convergence profiles, we constrain the central electron overdensity and temperature to be $\delta = 5.90^{+4.18}_{-1.98}$ and $T_e = 2.71^{+0.63}_{-0.51} \times 10^6$ K for the standard $\beta$-model. These results suggest that the filamentary WHIM in our selected long filaments contributes a significant baryon fraction of $0.124^{+0.020}_{-0.021} \times$ {\Omega}_b to the cosmic baryon budget.