Zhang, TJ , Beijing Normal Univ, Dept Astron, Beijing 100875, Peoples R China
部门归属:
Beijing Normal Univ, Dept Astron, Beijing 100875, Peoples R China; Univ Arizona, Dept Phys, Tucson, AZ 85721 USA; Purple Mt Observ, Nanjing 210008, Peoples R China; Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China; Chinese Acad Sci, Inst Theoret Phys, Beijing 100080, Peoples R China
英文摘要:
We study the X-ray emission of baryon fluid in the universe using the WIGEON cosmological hydrodynamic simulations. It has been revealed that cosmic baryon fluid in the nonlinear regime behaves like Burgers turbulence, i.e., the fluid field consists of shocks. Like turbulence in incompressible fluid, the Burgers turbulence plays an important role in converting the kinetic energy of the fluid to thermal energy and heats the gas. We show that the simulation sample of the Lambda CDMmodel without adding extra heating sources can fit well the observed distributions of X-ray luminosity versus temperature (L-X vs. T) of galaxy groups and is also consistent with the distributions of X-ray luminosity versus velocity dispersion (L-X vs. sigma). Because the baryonic gas is multiphase, the L-X-T and L-X-sigma distributions are significantly scattered. If we describe the relationships by power laws L-X alpha T-alpha LT and L-X alpha sigma(alpha LV), we find alpha(LT) > 2: 5 and alpha(LV) > 2:1. The X-ray background in the soft 0.5-2 keV band emitted by the baryonic gas in the temperature range 10(5) < T < 10(7) K has also been calculated. We show that of the total background, ( 1) no more than 2% comes from the region with temperature less than 10(6.5) K, and ( 2) no more than 7% is from the region of dark matter with mass density rho dm < 50 (rho) over bar (dm). The region of rho dm > 50 (rho) over bar (dm) is generally clustered and discretely distributed. Therefore, almost all of the soft X-ray background comes from clustered sources, and the contribution from truly diffuse gas is probably negligible. This point agrees with current X-ray observations.
Zhang, TJ,Liu, JR,Feng, LL,et al. X-ray emission of baryonic gas in the universe: Luminosity-temperature relationship and soft-band background[J]. ASTROPHYSICAL JOURNAL,2006,642(2):625-635.
