Power spectrum and intermittency of the transmitted flux from the Lyman   absorption spectra of quasi-stellar objects

Jamkhedkar, Priya; Feng, Long-Long; Zheng, Wei; Kirkman, David; Tytler, David; Fang, Li‐Zhi

doi:10.1046/j.1365-8711.2003.06662.x

Cited by 16 publications

(25 citation statements)

References 34 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: 53%

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: 53%

The Velocity Field of Baryonic Gas in the Universe

Kim¹,

He²,

Pando³

et al. 2005

ApJ

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“…3bfig. 3c ) 2 i by a factor of 20-30. This is in agreement with the result based on Keck data (Jamkhedkar et al 2003).…”

Section: Pdf Of F Jlsupporting

confidence: 93%

“…This approach is not new. The intermittency of Ly transmitted flux has been studied using the absorption spectra of QSOs (Jamkhedkar et al 2000(Jamkhedkar et al , 2003. The results have also been compared with simulations of the standard ÃCDM model and the warm dark matter model (Pando et al 2002;Feng et al 2003).…”

Section: Introductionmentioning

confidence: 99%

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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“…For instance, the lognormal clustering model of the IGM (Bi 1993; Bi & Davidsen 1997; Liu, Bi & Fang 2007; Feng et al 2008) can explain well all the basic properties of the Lyα forests of a quasar's absorption spectrum at various redshifts. However, high‐order statistics do reveal the deviation of observations from the lognormal model (Jamkhedkar et al 2003; Lu, Chu & Fang 2009).…”

Section: Introductionmentioning

confidence: 99%

Log-Poisson non-Gaussianity of Lyα transmitted flux fluctuations at high redshift

Lu¹,

Zhu²,

Chu³

et al. 2010

Monthly Notices of the Royal Astronomical Society

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We investigate the non‐Gaussian features of the intergalactic medium (IGM) at redshift z∼ 5–6 using the Lyα transmitted flux of quasar absorption spectra and a cosmological hydrodynamic simulation of the concordance ΛCDM universe. We show that the neutral hydrogen mass density field and Lyα transmitted flux fluctuations possess all the non‐Gaussian features predicted by the log‐Poisson hierarchy. This depends only on two dimensionless parameters β and γ, describing, respectively, the intermittence and singularity of the random fields. We find that the non‐Gaussianity of the Lyα transmitted flux of quasars from z= 4.9 to z= 6.3 can be well reconstructed by the hydrodynamical simulation samples. Although the Gunn–Peterson optical depth and its variance undergoes a significant evolution in the redshift range of 5–6, the intermittency measured by β is almost redshift‐independent in this range. More interestingly, the intermittency of the quasar's absorption spectra on physical scales 0.1–1 h−1 Mpc in redshift 5–6 is found to be about the same as that on physical scales 1–10 h−1 Mpc at redshifts 2–4. Considering the Jeans length is less than 0.1 h−1 Mpc at z∼ 5, and 1 h−1 Mpc at z∼ 2, these results imply that the non‐linear evolution in high and low redshifts will lead the cosmic baryon fluid to a state similar to fully developed turbulence. The log‐Poisson high‐order behaviour of the current high‐redshift data of a quasar's spectrum can be explained by the uniform ultraviolet background in the redshift range considered. We have also studied the log‐Poisson non‐Gaussianity by considering an inhomogeneous background. With several simplified models of the inhomogeneous background, we have found that the effect of the inhomogeneous background on the log‐Poisson non‐Gaussianity is no larger than 1σ.

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Power spectrum and intermittency of the transmitted flux from the Lyman absorption spectra of quasi-stellar objects

Cited by 16 publications

References 34 publications

The Velocity Field of Baryonic Gas in the Universe

The Velocity Field of Baryonic Gas in the Universe

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

Log-Poisson non-Gaussianity of Lyα transmitted flux fluctuations at high redshift

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