Thermal Energy Census with the Sunyaev–Zel’dovich Effect of DESI Galaxy Clusters/Groups and Its Implication on the Weak-lensing Power Spectrum

We carry out a thermal energy census of hot baryons at z < 1, by cross correlating the Planck Modified Internal Linear Combination Algorithm (MILCA) y map with 0.8 million clusters/groups selected from the Yang et al. catalog. The thermal Sunyaev–Zel’dovich effect around these clusters/groups is reliably obtained, which enables us to make our model constraints based on one-halo (1h) and two-halo (2h) contributions, respectively. (1) The total measurement signal-to-noise (S/N) of the one-halo term is 63. We constrain the Y–M relation over the halo mass range of 1013–1015 M ⊙ h −1, and find Y ∝ M α with α = 1.8 at z = 0.14 (α = 2.1 at z = 0.75). The total thermal energy of gas bound to clusters/groups increases from 0.1 meV cm−3 at z = 0.14 to 0.22 meV cm−3 at z = 0.75. (2) The 2h term is used to constrain the bias-weighted electron pressure 〈b y P e 〉. We find that 〈b y P e 〉 (in units of meV cm−3) increases from 0.24 ± 0.02 at z = 0.14 to 0.45 ± 0.02 at z = 0.75. These results lead to several implications. (i) The hot gas fraction f gas in clusters/groups monotonically increase with the halo mass, where f gas of a 1014 M ⊙ h −1 halo is ∼50% (25%) of the cosmic mean at z = 0.14 (0.75). (ii) By comparing the 1h and 2h terms, we obtain a tentative constraint on the thermal energy of unbound gas. (iii) The above results lead to significant suppression of the matter and weak-lensing power spectrum at small scales. These implications are important for astrophysics and cosmology, and we will further investigate them with improved data and gas modeling.