Open AccessThe temperature of the intergalactic medium and the Compton y parameter
Author(s) -
Zhang Pengjie,
Pen UeLi,
Trac Hy
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.08328.x
Subject(s) - physics , cmb cold spot , cosmology , astrophysics , adiabatic process , cold dark matter , dark matter , universe , reionization , statistical physics , computational physics , cosmic microwave background , redshift , thermodynamics , quantum mechanics , galaxy , anisotropy
The thermal Sunyaev–Zeldovich (SZ) effect directly probes the thermal energy of the Universe. Its precision modelling and future high‐accuracy measurements will provide a powerful way to constrain the thermal history of the Universe. In this paper, we focus on the precision modelling of the gas density weighted temperature and the mean SZ Compton y parameter. We run high‐resolution adiabatic hydrodynamic simulations adopting the WMAP cosmology to study the temperature and density distribution of the intergalactic medium (IGM). To quantify possible simulation limitations, we run n =−1, − 2 self‐similar simulations. Our analytical model on is based on energy conservation and matter clustering and has no free parameter. Combining both simulations and analytical models thus provides the precision modelling of and . We find that the simulated temperature probability distribution function and shows good convergence. For the WMAP cosmology, our highest‐resolution simulation (1024 3 cells, 100 Mpc h −1 box size) reliably simulates with better than 10 per cent accuracy for z ≳ 0.5 . Toward z = 0 , the simulation mass‐resolution effect becomes stronger and causes the simulated to be slightly underestimated (at z = 0 , ∼20 per cent underestimated). Since is mainly contributed by the IGM at z ≳ 0.5 , this simulation effect on is no larger than ∼10 per cent. Furthermore, our analytical model is capable of correcting this artefact. It passes all tests of self‐similar simulations and WMAP simulations and is able to predict and to several per cent accuracy. For a low matter density ΛCDM cosmology, the present is 0.32 (σ 8 /0.84) 3.05‐0.15 Ω m(Ω m /0.268) 1.28‐0.2 σ 8keV , which accounts for 10 −8 of the critical cosmological density and 0.024 per cent of the cosmic microwave background (CMB) energy. The mean y parameter is 2.6 × 10 −6 (σ 8 /0.84) 4.1‐2 Ω m(Ω m /0.268) 1.28‐0.2 σ 8. The current upper limit of y < 1.5 × 10 −5 measured by FIRAS has already ruled out combinations of high σ 8 ≳ 1.1 and high Ω m ≳ 0.5 .