The Intermittent Behavior of the Cosmic Mass Field Revealed by a L[CLC]y[/CLC]α Forest QSO

Jamkhedkar, Priya; Zhan, Hongbing; Fang, Li‐Zhi

doi:10.1086/312946

Cited by 21 publications

(23 citation statements)

References 15 publications

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“…For example, the transmitted flux of a QSO's Ly absorption is found to be significantly intermittent, and its probability distribution functions ( pdf ) are long tailed and probably lognormal (Jamkhedkar et al 2000(Jamkhedkar et al , 2003Pando et al 2002;Feng et al 2003). This is consistent with the intermittent spatial and temporal behavior of a developed Burgers fluid ( Polyakov 1995;Bouchaud et al 1995;Gurarie & Migdal 1996;Balkovsky et al 1997;Yakhot 1998;Frisch et al 2001).…”

Section: Introductionsupporting

confidence: 54%

The Velocity Field of Baryonic Gas in the Universe

Kim¹,

He²,

Pando³

et al. 2005

ApJ

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The dynamic evolution of the baryonic intergalactic medium ( IGM) caused by the underlying dark matter gravity is governed by the Navier-Stokes equations in which many cooling and heating processes are involved. However, it has long been recognized that the growth mode dynamics of cosmic matter clustering can be sketched by a random force driven Burgers equation if cooling and heating are ignored. Just how well the dynamics of the IGM can be described as a Burgers fluid has not been fully investigated, probably because cooling and heating are essential for a detailed understanding of the IGM. Using IGM samples produced by a cosmological hydrodynamic simulation in which heating and cooling processes are properly accounted for, we show that the IGM velocity field in the nonlinear regime shows the features of a Burgers fluid, that is, when the Reynolds number is high, the velocity field consists of an ensemble of shocks. Consequently, (1) the IGM velocity v is generally smaller than that of dark matter; (2) for the smoothed field, the IGM velocity shows tight correlation with dark matter given by v ' sv dm , with s < 1, such that the lower the redshift, the smaller the s; (3) the velocity probability density functions ( pdf's) are asymmetric between acceleration and deceleration events; (4) the pdf of velocity difference Áv ¼ v(x þ r) À v(x) satisfies the scaling relation for a Burgers fluid, i.e., P(Áv) ¼ (1/r y )F(Áv/r y ). We find the scaling function and parameters for the IGM that are applicable to the entire scale range of the samples (0.26-8 h À1 Mpc). These properties show that the similarity mapping between the IGM and dark matter is violated on scales much larger than the Jeans length of the IGM. Subject headingg s: cosmology: theory -intergalactic medium -large-scale structure of universe

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Section: Introductionsupporting

confidence: 54%

The Velocity Field of Baryonic Gas in the Universe

Kim¹,

He²,

Pando³

et al. 2005

ApJ

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“…For example, the Ly transmitted flux in the absorption spectra of QSOs is found to be significantly intermittent, and its probability distribution functions (PDFs) are remarkably long tailed (Jamkhedkar et al 2000;Pando et al 2002;Feng et al 2003). 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).…”

Section: Introductionmentioning

confidence: 97%

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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“…The local power spectrum of the underlying mass Ðeld of a QSOÏs Lya forest has been recently analyzed (Jamkhedkar, Zhan, & Fang 2000). It is found that the local power spectrum of the transmitted Ñux of the QSOÏs absorption shows prominent spiky structures on small scales.…”

Section: Introductionmentioning

confidence: 99%

The Local Power Spectrum and Correlation Hierarchy of the Cosmic Mass Field

Zhan

Jamkhedkar

Fang

2001

ApJ

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We analyze the power spectrum of a QSOÏs Lya-transmitted Ñux in the discrete wavelet transform (DWT) representation. Although the mean DWT power spectrum is consistent with its counterpart in Fourier representation, the spatial distribution of the local power varies greatly ; i.e., the local DWT power spectra show remarkably spiky structures on small scales. To measure these spiky features, we introduce the quantities roughness of the local power spectrum and correlation between spikes on di †er-ent scales. We then test the predictions made by the correlation hierarchy model on the roughness and the scale-scale correlations of the local power spectrum. Using the Lya-transmitted Ñux of the QSO HS 1700, we Ðnd that the underlying cosmic mass Ðeld of the transmitted Ñux at redshift around z^2.2 can be described by the hierarchical clustering model on physical scales from 2.5 h~1 Mpc to a few tens h~1 kpc in an EinsteinÈde Sitter universe. However, the nonlinear features of the clustering show di †erences on di †erent scale ranges : (1) On physical scales larger than D1.3 h~1 Mpc, the Ðeld is almost Gaussian.(2) On scales 1.3È0.3 h~1 Mpc, the Ðeld is consistent with the correlation hierarchy with a constant value for the coefficient (3) On scales less than 300 h~1 kpc, the Ðeld is no longer Gaussian but essentially Q 4 . intermittent. In this case, the Ðeld can still be Ðtted by the correlation hierarchy, but the coefficient, Q 4 , should be scale dependent. These three points are strongly supported by the following result : the scale dependencies of given by two statistically independent measures, i.e., by roughness and by Q 4 Q 4 R Q 4 C scale-scale correlation, are the same in the entire scale range considered.

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The Intermittent Behavior of the Cosmic Mass Field Revealed by a L[CLC]y[/CLC]α Forest QSO

Cited by 21 publications

References 15 publications

The Velocity Field of Baryonic Gas in the Universe

The Velocity Field of Baryonic Gas in the Universe

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

The Local Power Spectrum and Correlation Hierarchy of the Cosmic Mass Field

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