The thermal and gravitational energy densities in the large-scale structure of the Universe

Yi-Kuan Chiang; Ryu Makiya; Eiichiro Komatsu; Brice Ménard

doi:10.3847/1538-4357/abe387

paper

The thermal and gravitational energy densities in the large-scale structure of the Universe

arXiv:2007.01679 · doi:10.3847/1538-4357/abe387

Abstract

As cosmic structures form, matter density fluctuations collapse gravitationally and baryonic matter is shock-heated and thermalized. We therefore expect a connection between the mean gravitational potential energy density of collapsed halos, $Ω_{W}^{halo}$ , and the mean thermal energy density of baryons, $Ω_{th}$ . These quantities can be obtained using two fundamentally different estimates: we compute $Ω_{W}^{halo}$ using the theoretical framework of the halo model which is driven by dark matter statistics, and measure $Ω_{th}$ using the Sunyaev-Zeldovich (SZ) effect which probes the mean thermal pressure of baryons. First, we derive that, at the present time, about 90% of $Ω_{W}^{halo}$ originates from massive halos with $M > 1 0^{13} M_{⊙}$ . Then, using our measurements of the SZ background, we find that $Ω_{th}$ accounts for about 80% of the kinetic energy of the baryons available for pressure in halos at $z ≲ 0.5$ . This constrains the amount of non-thermal pressure, e.g., due to bulk and turbulent gas motion sourced by mass accretion, to be about $Ω_{non - th} ≃ 0.4 \times 1 0^{- 8}$ at $z = 0$ .

arXiv comment11 pages + references, 4 figures, 2 tables. (v2) Expanded discussion on the modelling uncertainty. (v3) Fixed a minor typo in Eq.(22). Accepted for publication in the Astrophysical Journal. Julia codes to reproduce the figures and tables are available in https://github.com/komatsu5147/OmegaGrav.jl

The thermal and gravitational energy densities in the large-scale structure of the Universe

Abstract

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