The Evolution of the Effective Equation of State of the Intergalactic Medium

Ricotti, Massimo; Gnedin, Nickolay Y.; Shull, J. M.

doi:10.1086/308733

Cited by 261 publications

(401 citation statements)

References 39 publications

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“…Combining the observations with the numerical simulations, Schaye et al (2000) found that b c at the fixed overdensity δ = 0, b δ=0 , increases from z ∼ 4.5 (b δ=0 ∼ 14.5 km s −1 ) to z ∼ 3 (b δ=0 ∼ 19.5 km s −1 ) due to He ii reionization at z ∼ 3 and then decreases from z ∼ 3 (b δ=0 ∼ 19.5 km s −1 ) to z ∼ 1.8 (b δ=0 ∼ 14 km s −1 ). Ricotti et al (2000) also found a similar increase in b δ=0 at z ∼ 3, although their b δ=0 at z > 2.8 and at z < 2.8 can be considered to be constant at b δ=0 ∼ 14.5 km s −1 and at b δ=0 ∼ 21 km s −1 , respectively. On the other hand, adopting a slightly different approach for identifying absorption lines instead of the Voigt profile fitting, McDonald et al (2000) found that there is no b c evolution over 2.1 < z < 4.4 at the slightly higher overdensity δ = 0.4.…”

Section: The Z-evolution Of B C (N H I )mentioning

confidence: 56%

“…The cutoff slope (Γ T −1) is proportional to (γ T − 1). This cutoff envelope provides a probe of the gas temperature of the IGM at a given z, thus giving a powerful constraint on the thermal history of the IGM Lu et al 1996;Kirkman & Tytler 1997;Zhang et al 1997;Schaye et al 1999;McDonald et al 2000;Ricotti et al 2000;Schaye et al 2000). In practice, defining b c (N H i ) in an objective manner is not trivial due to the finite number of available absorption lines, sightline-to-sightline cosmic variances, limited S/N , and unidentified metal lines.…”

Section: The Lower Cutoff B Parametermentioning

confidence: 99%

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The Lyαforest at $\mathsf{1.5 < {\vec z} < 4}$

Kim¹,

Cristiani

D’Odorico³

2001

A&A

119

191

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Abstract. Using high resolution (R ∼ 45 000), high S/N (∼20-50) VLT/UVES data, we have analyzed the Lyα forest of 3 QSOs in the neutral hydrogen (H i) column density range NH i = 10 12.5−16 cm −2 at 1.5 < z < 2.4. We combined our results with similar high-resolution, high S/N data in the literature at z > 2.4 to study the redshift evolution of the Lyα forest at 1.5 < z < 4. We have applied two types of analysis: the traditional Voigt profile fitting and statistics on the transmitted flux. The results from both analyses are in good agreement: 1. The differential column density distribution function, f (NH i), of the Lyα forest shows little evolution in the column density range NH i = 10 12.5−14 cm −2 , f (NH i) ∝ N −β H i , with β ∼ 1.4-1.5 at 1.5 < z < 4 and with a possible increase of β to β ∼ 1.7 at z < 1.8. A flattening of the power law slope at lower column densities at higher z can be attributed to more severe line blending. A deficiency of lines with NH i > 10 14 cm −2 is more noticeable at lower z than at higher z. The one-point function and the two-point function of the flux confirm that strong lines do evolve faster than weak lines; 2. The line number density per unit redshift, dn/dz, at NH i = 10 13.64−16 cm −2 is well fitted by a single power law, dn/dz ∝ (1 + z) 2.19±0.27 , at 1.5 < z < 4. In combination with the HST results from the HST QSO absorption line key project, the present data indicate that a flattening in the number density evolution occurs at z ∼ 1.2. The line counts as a function of the filling factor at the transmitted flux F in the range 0 < F < 0.9 are constant in the interval 1.5 < z < 4. This suggests that the Hubble expansion is the main drive governing the forest evolution at z > 1.5 and that the metagalactic UV background changes more slowly than a QSO-dominated background at z < 2; 3. The observed cutoff Doppler parameter at the fixed column density NH i = 10 13.5 cm −2 , bc,13.5, shows a weak increase with decreasing z, with a possible local bc,13.5 maximum at z ∼ 2.9; 4. The two-point velocity correlation function and the step optical depth correlation function show that the clustering strength increases as z decreases; 5. The evolution of the mean H i opacity, τ H i, is well approximated by an empirical power law, τ H i ∝ (1+z) 3.34±0.17 , at 1.5 < z < 4; 6. The baryon density, Ω b , derived both from the mean H i opacity and from the one-point function of the flux is consistent with the hypothesis that most baryons (over 90%) reside in the forest at 1.5 < z < 4, with little change in the contribution to the density, Ω, as a function of z.

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Section: The Z-evolution Of B C (N H I )mentioning

confidence: 56%

Section: The Lower Cutoff B Parametermentioning

confidence: 99%

The Lyαforest at $\mathsf{1.5 < {\vec z} < 4}$

Kim¹,

Cristiani

D’Odorico³

2001

A&A

119

191

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“…(1)), which is thought to arise from the competition between photoheating and cooling due to the adiabatic expansion of the Universe, following reionization. The evolution of this relation has been measured in the data and depends on the reionization history and the hardness of the UV background (Schaye et al 2000;Ricotti et al 2000;Rollinde et al 2013), although in reality the picture is more complicated -because of radiative transfer effects during the epoch of HeII reionization. Nevertheless, the temperature at the characteristic overdensity probed by the Lyα is now quite well measured (e.g.…”

Section: Visualizationsmentioning

confidence: 99%

Suite of hydrodynamical simulations for the Lyman-αforest with massive neutrinos

Rossi

Palanque-Delabrouille

Borde

et al. 2014

A&A

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The signature left in quasar spectra by neutral hydrogen in the Universe allows constraining the sum of the neutrino masses with a better sensitivity than laboratory experiments and may shed new light on the neutrino mass hierarchy and the absolute mass-scale of neutrinos. Constraints on cosmological parameters and on the dark energy equation of state can also be derived from a joint parameter estimation procedure. However, this requires a detailed modeling of the line-of-sight power spectrum of the transmitted flux in the Lyman-α (Lyα) forest on scales ranging from a few to hundreds of megaparsecs, which in turn demands the inclusion and careful treatment of cosmological neutrinos. To this end, we present here a suite of state-of-the-art hydrodynamical simulations with cold dark matter (CDM), baryons and massive neutrinos, specifically targeted for modeling the low-density regions of the intergalactic medium (IGM) as probed by the Lyα forest at high-redshift. The simulations span volumes ranging from (25 h −1 Mpc) 3 to (100 h −1 Mpc) 3 , and were made using either 3 × 192 3 21 million or 3 × 768 3 1.4 billion particles. The resolution of the various runs was further enhanced, so that we reached the equivalent of 3 × 3072 3 87 billion particles in a (100 h −1 Mpc) 3 box size. The chosen cosmological parameters are compatible with the latest Planck 2013 results, although we also explored the effect of slight variations in the main cosmological and astrophysical parameters. We adopted a particle-type implementation of massive neutrinos, and consider three degenerate species with masses m ν = 0.1, 0.2, 0.3, 0.4, and 0.8 eV, respectively. We improved on previous studies in several ways, in particular with updated routines for IGM radiative cooling and heating processes, and initial conditions based on second-order Lagrangian perturbation theory (2LPT) rather than the Zel'dovich approximation. This allowed us to safely start our runs at relatively low redshift (z = 30), which reduced the shot-noise contamination in the neutrino component and the CPU consumption. In addition to providing technical details on the simulations, we present the first analysis of the nonlinear three-and one-dimensional matter and flux power spectra from these models, and characterize the statistics of the transmitted flux in the Lyα forest including the effect of massive neutrinos. In synergy with recent data from the Baryon Acoustic Spectroscopic Survey (BOSS) and the Planck satellite, and with a grid of corresponding neutrino-less simulations, our realizations will allow us to constrain cosmological parameters and neutrino masses directly from the Lyα forest with improved sensitivity. In addition, our simulations can be useful for a broader variety of cosmological and astrophysical applications, ranging from the three-dimensional modeling of the Lyα forest to cross-correlations between different probes, studying the expansion history of the Universe including massive neutrinos, and particle-physics related topics. Moreover, while ...

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“…Another difficulty is that observations of the Lya forest indicate a much lower temperature for the majority of the intergalactic medium at (Bryan z ∼ 2-3 1 Hubble Fellow. & Machacek 2000; Schaye et al 1999), a condition that may extend to even lower redshifts (Ricotti, Gnedin, & Shull 2000). Although hardly conclusive, these concerns may be pointing toward another explanation for the observations.…”

Section: Introductionmentioning

confidence: 95%

Explaining the Entropy Excess in Clusters and Groups of Galaxies without Additional Heating

Bryan¹

2000

The Astrophysical Journal

139

172

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The X-ray luminosity and temperature of clusters and groups of galaxies do not scale in a self-similar manner. This has often been interpreted as a sign that the intracluster medium has been substantially heated by nongravitational sources. In this Letter, we propose a simple model that instead uses the properties of galaxy formation to explain the available observations. Drawing on available observations, we show that there is evidence that the efficiency of galaxy formation was higher in groups than in clusters. If confirmed, this would deplete the low-entropy gas in groups, increase their central entropy, and decrease their X-ray luminosity. A simple, empirical, hydrostatic model appears to match both the luminosity-temperature relation of clusters and the properties of their internal structure.

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The Evolution of the Effective Equation of State of the Intergalactic Medium

Cited by 261 publications

References 39 publications

The Lyαforest at $\mathsf{1.5 < {\vec z} < 4}$

The Lyαforest at $\mathsf{1.5 < {\vec z} < 4}$

Suite of hydrodynamical simulations for the Lyman-αforest with massive neutrinos

Explaining the Entropy Excess in Clusters and Groups of Galaxies without Additional Heating

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