The Velocity Field of Baryonic Gas in the Universe

Kim, Bryan; He, Pinjia; Pando, Jesus; Feng, Long-Long; Fang, Li‐Zhi

doi:10.1086/429556

Cited by 12 publications

(25 citation statements)

References 54 publications

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“…The H i and He ii Ly absorption lines of QSO HE 2347 cannot be explained by thermal broadening, but are consistent with turbulence broadening ( Zheng et al 2004;Liu et al 2006). Moreover, samples produced by cosmological hydrodynamic simulations also reveal the statistical decoupling of baryon matter from dark matter and the non-Gaussian features of Bergers' turbulence (He et al 2004Kim et al 2005).…”

Section: Introductionsupporting

confidence: 58%

Non‐Gaussianity of the Cosmic Baryon Fluid: Log‐Poisson Hierarchy Model

Liu

Fang

2008

ApJ

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In the nonlinear regime of cosmic clustering, the mass density field of the cosmic baryon fluid is highly nonGaussian. It shows different dynamical behavior from collisionless dark matter. Nevertheless, the evolved field of the baryon fluid is scale-covariant in the range from the Jeans length to a few tens of h À1 Mpc, within which the dynamical equations and initial perturbations are scale free. We show that in the scale-free range, the non-Gaussian features of the cosmic baryon fluid, governed by the Navier-Stokes equation in an expanding universe, can be well described by a log-Poisson hierarchical cascade. The log-Poisson scheme is a random multiplicative process (RMP), which causes non-Gaussianity and intermittency even when the original field is Gaussian. The log-Poisson RMP contains two dimensionless parameters: for the intermittency and for the most singular structure. All the predictions given by the logPoisson RMP model, including the hierarchical relation, the order dependence of the intermittent exponent, the moments, and the scale-scale correlation, are in good agreement with the results given by hydrodynamic simulations of the standard cold dark matter model. The intermittent parameter decreases slightly at low redshift and indicates that the density field of the baryon fluid contains more singular structures at lower redshifts. The applicability of the model is addressed. Subject headingg s: cosmology: theory -large-scale structure of universe

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Section: Introductionsupporting

confidence: 58%

Non‐Gaussianity of the Cosmic Baryon Fluid: Log‐Poisson Hierarchy Model

Liu

Fang

2008

ApJ

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“…It has been shown recently that in the nonlinear regime the velocity field v(x) of cosmic baryon matter consists of strong shocks on various spatial scales and in high and low mass density area ( Kim et al 2005). The statistical behavior of the velocity field is similar to a fully developed turbulence (He et al 2006).…”

Section: Introductionmentioning

confidence: 99%

A Unified Fitting of Hiand HeiiLyα Transmitted Flux of QSO HE 2347−4342 with ΛCDM Hydrodynamic Simulations

Liu

Jamkhedkar

Zheng

et al. 2006

ApJ

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Using cosmological hydrodynamic simulations of the ÃCDM model, we present a comparison between the simulation sample and real data sample of H i and He ii Ly transmitted flux in the absorption spectra of the QSO HE 2347À4342. The ÃCDM model is successful in simultaneously explaining the statistical features of both H i and He ii Ly transmitted flux. It includes the following features: (1) The power spectra of the transmitted flux of H i and He ii can be well fitted on all scales !0.28 h À1 Mpc for H and !1.1 h À1 Mpc for He. (2) The Doppler parameters of absorption features of He ii and H i are found to be turbulent broadening. (3) The ratio of He ii to H i optical depths are substantially scattered, due to the significant effect of noise. A large part of the scatter is due to the noise in the He ii flux. However, the real data contain more low-events than the simulation sample. This discrepancy may indicate that the mechanism leading extra fluctuations on the simulation data, such as a fluctuating UV radiation background, is needed. Yet models of these extra fluctuations should satisfy the following constraints: (1) If the fluctuations are Gaussian, they should be limited by the power spectra of observed H i and He ii flux. (2) If the fluctuations are nonGaussian, they should be limited by the observed non-Gaussian features of the H i and He ii flux. Subject headingg s: cosmology: theory -large-scale structure of universe

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“…Therefore, the field of the transmitted flux fluctuations is highly intermittent. This shows again that the cuspy feature of cosmic clustering can be seen in high mass density areas, like massive halos, as well as in low mass density areas, like the clouds of Ly absorption clouds (Pando et al 2004;He et al 2004He et al , 2005Kim et al 2005). Actually, the success of the semianalytical lognormal model (Bi & Davidsen 1997) in explaining the Ly forest has already indicated that the mass field of the cosmic baryon gas is probably intermittent, because a lognormal field is intermittent.…”

Section: Structure Functionsmentioning

confidence: 82%

“…If the index is constant, the intermittency exponent should be scale-independent. Therefore, the scale dependence of the intermittency exponent indicates that the distribution of baryon gas is decoupled from the underlying dark matter (e.g., He et al 2004;Kim et al 2005). The data of HE 2347À4342 only are unable to test the prediction of scale dependence of the intermittency exponent.…”

Section: Discussionmentioning

confidence: 99%

“…For details of the numerical method and tests, we refer to Feng et al (2004). The simulation sample we analyze here is actually the same as those used in our previous papers on the statistical study of temperature, entropy, baryonic fraction, and velocity fields of intergalactic medium ( He et al 2004Kim et al 2005). It was performed in a cubic box of side length 12 h À1 Mpc with a 192 3 grid and an equal number of dark matter particles.…”

Section: Hydrodynamic Simulationmentioning

confidence: 99%

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Power Spectrum and Intermittency of Lyα Transmitted Flux of QSO HE 2347−4342

Jamkhedkar

Feng

Zheng

et al. 2005

ApJ

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We have studied the power spectrum and the intermittent behavior of the fluctuations in the transmitted flux of HE 2347À4342 Ly absorption in order to investigate if there is any discrepancy between the ÃCDM model with parameters given by the WMAP and observations on small scales. If the non-Gaussianity of the cosmic mass field is assumed to come only from halos with a universal mass profile of the ÃCDM model, the non-Gaussian behavior of mass field would be effectively measured by its intermittency, because intermittency is a basic statistical feature of the cuspy structures. We have shown that the Ly transmitted flux field of HE 2347À4342 is significantly intermittent on small scales. With the hydrodynamic simulation, we demonstrate that the ÃCDM model is successful in explaining the power spectrum and intermittency of Ly transmitted flux. Using statistics ranging from second to eighth order, we find no discrepancy between the ÃCDM model and the observed transmitted flux field and no evidence to support the necessity of reducing the power of density perturbations relative to the standard ÃCDM model up to comoving scales as small as about 0.08 h À1 Mpc. Moreover, our simulation samples show that the intermittency exponent of the Ly transmitted flux field is probably scale-dependent. This result is different from the prediction of a universal mass profile with a constant power index of the central cusp. The scale dependence of the intermittency exponent indicates that the distribution of baryonic gas is decoupled from the underlying dark matter. Subject headingg s: cosmology: theory -large-scale structure of universe

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The Velocity Field of Baryonic Gas in the Universe

Cited by 12 publications

References 54 publications

Non‐Gaussianity of the Cosmic Baryon Fluid: Log‐Poisson Hierarchy Model

Non‐Gaussianity of the Cosmic Baryon Fluid: Log‐Poisson Hierarchy Model

A Unified Fitting of Hiand HeiiLyα Transmitted Flux of QSO HE 2347−4342 with ΛCDM Hydrodynamic Simulations

Power Spectrum and Intermittency of Lyα Transmitted Flux of QSO HE 2347−4342

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