The thermal history of cosmic gas in the Dark Ages remains largely unknown. It is important to quantify the impact of relevant physics on the IGM temperature between $z=10$ and $z \sim 30$, in order to interpret recent and oncoming observations, including results reported by EDGES. We revisit the gas heating due to structure formation shocks in this era, using a set of fixed grid cosmological hydrodynamical simulations performed by three different codes. In all our simulations, the cosmic gas is predicted to be in multiphase state since $z>30$. The gas surrounding high density peaks gradually develops a relation more sharp than $T \propto ρ^{2/3}$, approximately $T \propto ρ^{2}$, from $z=30$ to $z=11$, might due to shock heating. Meanwhile, the gas in void region tends to have a large local mach number, and their thermal state varies significantly from code to code. In the redshift range $11-20$, the mass fraction of gas shock heated above the CMB temperature in our simulations is larger than previous semi-analytical results by a factor of 2 to 8. At $z=15$, the fraction varies from $\sim 19\%$ to $52 \%$ among different codes. Between $z=11$ and $z=20$, the gas temperature $<1/T_{\rm{K}}>_M^{-1}$ is predicted to be $\sim 10-20$ K by two codes, much higher than the adiabatic cooling model and some previous works. However, in our simulations performed by RAMSES, $<1/T_{\rm{K}}>_M^{-1}$ is predicted to be even below the temperature required to explain result of the EDGES. Given the fact that different codes give different predictions, currently, it seems a challenge to make solid prediction on the temperature of gas at $z \sim 17$ in simulations.
Observations of the 21 cm line from neutral hydrogen indicate that an Epoch of Heating (EoH) might have preceded the later Epoch of Reionization (EoR). Here we study the effects on the ionization state and the thermal history of the Intergalactic Medium (IGM) during the EoH induced by different assumptions on ionizing sources in the high redshift Universe: (i) stars, (ii) X-ray binaries (XRBs), (iii) thermal bremsstrahlung of the hot Interstellar Medium (ISM), and (iv) accreting nuclear black holes (BHs). To this aim, we post-process outputs from the ($100 h^{-1}$ cMpc)$^3$ hydrodynamical simu…
The intergalactic medium (IGM) acts like a calorimeter recording energy injection by cosmic structure formation, shocks and photoheating from stars and active galactic nuclei. It was recently proposed that spatially inhomogeneous TeV-blazars could significantly heat up the underdense IGM, resulting in patches of both cold and warm IGM around $z\simeq2-3$. The goal of this study is to compare predictions of different blazar heating models with recent observations of the IGM. We perform a set of cosmological simulations and carefully compute mock observables of the Lyman-$α ($Ly$α$) forest. We p…
It is extremely important to understand the processes through which the thermal state of the inter-galactic medium (IGM) evolved in the early universe in order to study the evolution of HI 21-cm signal during cosmic dawn. Here, we consider the heating of the IGM due to cosmic ray protons generated by the supernovae from both early Pop III and Pop II stars. The low energy cosmic ray protons from Pop III supernovae can escape from minihalos and heat the IGM via collision and ionization of hydrogen. Furthermore, high energy protons generated in Pop II supernovae can escape the hosting halos and h…
We study the heating of the intergalactic medium (IGM) surrounding high redshift star forming galaxies due to cosmic rays (CR). We take into account the diffusion of low energy cosmic rays and study the patchiness of the resulting heating. We discuss the case of IGM heating around a high redshift minihalo ($z\sim 10\hbox{--}20$, M$\sim 10^5\hbox{--}10^7$ M$_\odot$),and put an upper limit on the diffusion coefficient $D\le 1\times 10^{26}$ cm$^2$ s$^{-1}$ for the heating to be inhomogeneous at $z\sim 10$ and $D\le 5\hbox{--}6 \times 10^{26}$ cm$^2$ s$^{-1}$ at $z\sim 20$. For typical values of …
A late end to reionisation at redshift $z\simeq 5.3$ is consistent with observed spatial variations in the Ly$α$ forest transmission and the deficit of Ly$α$ emitting galaxies around extended Ly$α$ absorption troughs at $z=5.5$. In this model, large islands of neutral hydrogen should persist in the diffuse intergalactic medium (IGM) until $z\simeq 6$. We use a novel, hybrid approach that combines high resolution cosmological hydrodynamical simulations with radiative transfer to predict the incidence of strong 21 cm forest absorbers with optical depths $τ_{21}>10^{-2}$ from the diffuse IGM in t…
The cosmic 21 cm signal is set to revolutionise our understanding of the early Universe, allowing us to probe the 3D temperature and ionisation structure of the intergalactic medium (IGM). It will open a window onto the unseen first galaxies, showing us how their UV and X-ray photons drove the cosmic milestones of the epoch of reionisation (EoR) and epoch of heating (EoH). To facilitate parameter inference from the 21 cm signal, we previously developed 21CMMC: a Monte Carlo Markov Chain sampler of 3D EoR simulations. Here we extend 21CMMC to include simultaneous modelling of the EoH, resulting…
The recent observation of the 21-cm global absorption signal by EDGES suggests that the intergalactic medium (IGM) gas has been cooler than the cosmic microwave background during $15 \lesssim z \lesssim 20$. This result can provide a strong constraint on heating sources for the IGM gas at these redshifts. In this paper we study the constraint on the primordial magnetic fields (PMFs) by the EDGES result. The PMFs can heat the IGM gas through their energy dissipation due to the magnetohydrodynamic effects. By numerically solving the thermal evolution of the IGM gas with the PMFs, we find that th…
We decompose the Lyman-α (Lyα) forest of an extensive sample of 74 high signal-to-noise ratio and high-resolution quasar spectra into a collection of Voigt profiles. Absorbers located near caustics in the peculiar velocity field have the smallest Doppler parameters, resulting in a low-$b$ cutoff in the $b$-$N_{\text{HI}}$ set by the thermal state of intergalactic medium (IGM). We fit this cutoff as a function of redshift over the range $2.0\leq z \leq 3.4$, which allows us to measure the evolution of the IGM temperature-density ($T= T_0 (ρ/ ρ_0)^{γ-1}$) relation parameters $T_0$ and $γ$. We ca…
High-energy emission associated with star formation has been proposed as a significant source of interstellar medium (ISM) ionization in low-metallicity starbursts and an important contributor to the heating of the intergalactic medium (IGM) in the high-redshift ($z > 8$) Universe. Using Chandra observations of a sample of 30 galaxies at $D \approx$~200--450 Mpc that have high specific star-formation rates of 3--9 Gyr$^{-1}$ and metallicities near $Z \approx 0.3 Z_\odot$, we provide new measurements of the average 0.5--8 keV spectral shape and normalization per unit star-formation rate (SFR). …
We characterise the thermal state of the intergalactic medium (IGM) in ten redshift bins in the redshift range $2 \leq z \leq 4$ with a sample of 103 high resolution, high S/N Ly$α$ forest spectra using four different flux distribution statistics. Our measurements are calibrated with mock spectra from a large suite of hydrodynamical simulations post-processed with our thermal IGM evolution code CITE, finely sampling amplitude and slope of the expected temperature-density relation. The thermal parameters inferred from our measurements of the flux power spectrum, Doppler parameter distribution, …
Ly$α$ forest absorption spectra decomposed into multiple Voigt profile components (clouds) allow us to study clustering of intergalactic medium (IGM) as a function of HI column density ($N_{\rm HI}$). Here, we explore the transverse three-point correlation ($ζ$) of these Ly$α$ clouds using mock triplet spectra obtained from hydrodynamical simulations at $z \sim 2$ on scales of 1-5 $h^{-1}$cMpc. We find $ζ$ to depend strongly on $N_{\rm HI}$ and scale and weakly on angle ($θ$) of the triplet configuration. We show that the "hierarchical ansatz" is applicable for scales $\ge~ 3h^{-1}$cMpc, and o…
Cross-correlating 21cm with known cosmic signals will be invaluable proof of the cosmic origin of the first 21cm detections. As some of the widest fields available, comprising thousands of sources with reasonably known redshifts, narrow-band Lyman alpha emitter (LAE) surveys are an obvious choice for such cross-correlation. Here we revisit the 21cm -- LAE cross-correlation, relaxing the common assumption of reionization occurring in a pre-heated intergalactic medium (IGM). Using specifications from the Square Kilometre Array and the Subary Hyper Supreme-Cam, we present new forecasts of the 21c…
X-rays from High-Mass X-ray Binaries (HMXBs) are likely the main source of heating of the intergalactic medium (IGM) during Cosmic Dawn (CD), before the completion of reionization. This Epoch of Heating (EoH; $z\sim 10-15$) should soon be detected via the redshifted 21-cm line from neutral hydrogen, allowing us to indirectly study the properties of HMXBs in the unseen, first galaxies. Low-redshift observations, as well as theoretical models, imply that the integrated X-ray luminosity to star formation rate of HMXBs ($L_{\rm X}/{\rm SFR}$) should increase in metal-poor environments, typical of …
We examine the impact of black hole jet feedback on the properties of the low-redshift intergalactic medium (IGM) in the SIMBA simulation, with a focus on the Ly$α$ forest mean flux decrement $D_A$. Without jet feedback, we confirm the Photon Underproduction Crisis (PUC) in which $Γ_{\rm HI}$ at $z=0$ must be increased by $\times6$ over the Haardt & Madau value in order to match the observed $D_{A}$. Turning on jet feedback lowers this discrepancy to $\sim\times 2.5$, and additionally using the recent Faucher-Giguère background mostly resolves the PUC, along with producing a flux probability d…
We derive constraints on the thermal and ionization states of the intergalactic medium (IGM) at redshift $\approx$ 9.1 using new upper limits on the 21-cm power spectrum measured by the LOFAR radio-telescope and a prior on the ionized fraction at that redshift estimated from recent cosmic microwave background (CMB) observations. We have used results from the reionization simulation code GRIZZLY and a Bayesian inference framework to constrain the parameters which describe the physical state of the IGM. We find that, if the gas heating remains negligible, an IGM with ionized fraction $\gtrsim 0.…
We report a $z=2.30$ galaxy protocluster (COSTCO-I) in the COSMOS field, where the Lyman-$α$ forest as seen in the CLAMATO IGM tomography survey does not show significant absorption. This departs from the transmission-density relationship (often dubbed the fluctuating Gunn-Peterson approximation; FGPA) usually expected to hold at this epoch, which would lead one to predict strong Ly$α$ absorption at the overdensity. For comparison, we generate mock Lyman-$α$ forest maps by applying FGPA to constrained simulations of the COSMOS density field, and create mocks that incorporate the effects of fin…
Kiloparsec-scale turbulence driven by reionization may grow intergalactic magnetic fields
School of Earth and Space exploration, Arizona State University（亚利桑那州立大学地球与空间探索学院）；Department of Astronomy, University of Washington（华盛顿大学天文学系）；Department of Physics and Astronomy, University of California, Riverside（加州大学河滨分校物理与天文系）；McWilliams Center for Cosmology and Astrophysics, Department of Physics, Carnegie Mellon University（卡内基梅隆大学物理系麦威廉斯宇宙学与天体物理学中心）
The latest measurements of CMB electron scattering optical depth reported by Planck significantly reduces the allowed space of HI reionization models, pointing toward a later ending and/or less extended phase transition than previously believed. Reionization impulsively heats the intergalactic medium (IGM) to $\sim10^4$ K, and owing to long cooling and dynamical times in the diffuse gas, comparable to the Hubble time, memory of reionization heating is retained. Therefore, a late ending reionization has significant implications for the structure of the $z\sim5-6$ Lyman-$α$ (ly$α$) forest. Using…
Recent observations suggest that hydrogen reionization ends late ($z \simeq 6$) and proceeds quickly. We present here a new model of the meta-galactic UV/X-ray background (UVB) that is consistent with this. It adopts the most recent determinations of the ionizing emissivity due to stars and AGN, as well as of the HI absorber column density distribution. Another major improvement is a new treatment of the intergalactic medium (IGM) opacity for ionizing photons that is able to consistently capture the transition from a neutral to an ionized IGM. Previous synthesis models of the UVB, when used in…
We examine the column density distribution function (CDDF) and Doppler parameter distribution from hydrodynamical simulations and Cosmic Origins Spectrograph (COS) observations of the Lyman-alpha forest at redshift $0\leq z\leq 0.2$. Allowing for a factor of two uncertainty in the metagalactic HI photoionisation rate, our hydrodynamical simulations are in good agreement ($1$-$1.5σ$) with the shape and amplitude of the observed CDDF at HI column densities $10^{13.3}\rm\,cm^{-2}\leq N_{\rm HI}\leq 10^{14.5}\rm\,cm^{-2}$. However, the Doppler widths of the simulated lines remain too narrow with r…
We examine the thermal energy contents of the intergalactic medium (IGM) over three orders of magnitude in both mass density and gas temperature using thermal Sunyaev-Zel'dovich effect (tSZE). The analysis is based on {\it Planck} tSZE map and the cosmic density field, reconstructed for the SDSS DR7 volume and sampled on a grid of cubic cells of $(1h^{-1}{\rm Mpc})^3$, together with a matched filter technique employed to maximize the signal-to-noise. Our results show that the pressure - density relation of the IGM is roughly a power law given by an adiabatic equation of state, with an indicati…
