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

作　　者：Jun-Yi Jia Wei-Shan Zhu Liang Gao Long-Long Feng 

机构地区：[1]Key Laboratory for Computational Astrophysics,National Astronomical Observatories,Chinese Academy of Sciences,Beijing 100101,China [2]School of Astronomy and Space Science,University of Chinese Academy of Sciences,Beijing 100049,China [3]School of Physics and Astronomy,Sun Yat-Sen University,Zhuhai 519082,China [4]Institute of Computational Cosmology,Department of Physics,University of Durham,South Road,Durham DH13LE,UK 5 Purple Mountain Observatory,Chinese Academy of Sciences,Nanjing 210008,China

出　　处：《Research in Astronomy and Astrophysics》2020年第6期253-264,共12页天文和天体物理学研究（英文版）

基　　金：supported by the National Key R&D Program of China(No.2017YFB0203300);and the Key Program of the National Natural Science Foundation of China(NFSC,Grant No.11733010);W.S.Z.acknowledges support from the NSFC(Grant No.11673077);F.L.L.is supported by the NSFC(Grant No.11333008);the State Key Development Program for Basic Research of China(2015CB857000)。

摘　　要：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^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∝ρ2/3,approximately T∝ρ2,from z=30 to z=11,might be 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^19%to 52%among different codes.Between z=11 and z=20,the gas temperature<1/TK>M-1 is predicted to be^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/TK>M-1is 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^17 in simulations.

关 键 词：COSMOLOGY theory-dark ages reionization first stars-galaxies high-redshift-intergalactic medium 

分 类 号：P159[天文地球—天文学]