The temperature of IGM at high redshifts: shock heating and high mach problem

Abstract

The thermal history of cosmic gas in the Dark Ages remains largely unknown. It is important to quantify the impact of relevant physics on the IGM temperature between $z=10$ and $z\sim 30$, in order to interpret recent and oncoming observations, including results reported by EDGES. We revisit the gas heating due to structure formation shocks in this era, using a set of fixed grid cosmological hydrodynamical simulations performed by three different codes. In all our simulations, the cosmic gas is predicted to be in multiphase state since $z>30$. The gas surrounding high density peaks gradually develops a relation more sharp than $T\propto {\rho }^{2/3}$, approximately $T\propto {\rho }^2$, from $z=30$ to $z=11$, might due to shock heating. Meanwhile, the gas in void region tends to have a large local mach number, and their thermal state varies significantly from code to code. In the redshift range $11-20$, the mass fraction of gas shock heated above the CMB temperature in our simulations is larger than previous semi-analytical results by a factor of 2 to 8. At $z=15$, the fraction varies from $\sim 19\%$ to $52\%$ among different codes. Between $z=11$ and $z=20$, the gas temperature $<1/T_{\mathrm{K}}{>}_M^{-1}$ is predicted to be $\sim 10-20$ K by two codes, much higher than the adiabatic cooling model and some previous works. However, in our simulations performed by RAMSES, $<1/T_{\mathrm{K}}{>}_M^{-1}$ is predicted to be even below the temperature required to explain result of the EDGES. Given the fact that different codes give different predictions, currently, it seems a challenge to make solid prediction on the temperature of gas at $z\sim 17$ in simulations.

arXiv comment18 pages, 9 figures , accepted by Research in Astronomy and Astronphysics

References in corpus (25)

• Planck 2013 results. XVI. Cosmological parameters
• Cosmological Hydrodynamics with Adaptive Mesh Refinement: a new high resolution code called RAMSES
• Radiative Transfer in a Clumpy Universe: II. The Utraviolet Extragalactic Background
• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• An absorption profile centred at 78 megahertz in the sky-averaged spectrum
• Where are the Baryons?
• Baryons in the Warm-Hot Intergalactic Medium
• 21-cm Tomography of the Intergalactic Medium at High Redshift
• Possible interaction between baryons and dark-matter particles revealed by the first stars
• The Baryon Census in a Multiphase Intergalactic Medium: 30% of the Baryons May Still Be Missing
• Gravitational Collapse of Small-Scale Structure as the Origin of the Lyman Alpha Forest
• The Opacity of the Lyman Alpha Forest and Implications for Omega_{baryon} and the Ionizing Background
• P3M-SPH simulations of the Lyman-alpha Forest
• The Evolution of the Intergalactic Medium
• The Search for the Missing Baryons at Low Redshift
• Observations of the MIssing Baryons in the warm-hot intergalactic medium
• Properties of Cosmic Shock Waves in Large Scale Structure Formation
• Enhanced global signal of neutral hydrogen due to excess radiation at cosmic dawn
• The Distribution of Column Densities and b Values in the Lyman-Alpha Forest
• Redshifted 21 cm Emission From the Pre-Reionization Era I. Mean Signal and Linear Fluctuations
• The impact of the supersonic baryon-dark matter velocity difference on the z~20 21cm background
• The formation of the first cosmic structures and the physics of the z~20 Universe
• Large-Scale Structure Shocks at Low and High Redshifts
• A Hybrid Cosmological Hydrodynamic/N-body Code Based on a Weighted Essentially Non-Oscillatory Scheme
• Turbulence in the Inter-galactic Medium: Solenoidal and Dilatational Motions, and the Impact of Numerical Viscosity

Cited by in corpus (2)

• The AGORA High-resolution Galaxy Simulations Comparison Project. III: Cosmological zoom-in simulation of a Milky Way-mass halo
• Resistive Heating Induced by Streaming Cosmic Rays Around a Galaxy in the Early Universe