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Abstract Using the novel semi-numerical code for reionization AMBER, we model the patchy kinetic Sunyaev–Zel’dovich (kSZ) effect by directly specifying the reionization history with the redshift midpointz_mid, duration Δ_z, and asymmetryA_z. We further control the ionizing sources and radiation through the minimum halo massM_hand the radiation mean free pathλ_mfp. AMBER reproduces the free-electron number density and the patchy kSZ power spectrum of radiation–hydrodynamic simulations at the target resolution (1 Mpch⁻¹) with matched reionization parameters. With a suite of (2 Gpc/h)³simulations using AMBER, we first constrain the redshift midpoint 6.0 <z_mid< 8.9 using the Planck 2018 Thomson optical depth result (95% CL). Then, assumingz_mid= 8, we find that the amplitude of $D_{\mathit{\ell }=3000}^{\mathrm{pkSZ}}$scales linearly with the duration of reionization Δ_zand is consistent with the 1σupper limit from South Pole Telescope (SPT) results up to Δ_z< 5.1 (Δ_zencloses 5%–95% ionization). Moreover, a shorterλ_mfpcan lead to a ∼10% lower $D_{\mathit{\ell }=3000}^{\mathrm{pkSZ}}$and a flatter slope in the $D_{\mathit{\ell }=3000}^{\mathrm{pkSZ}}-{\mathrm{\Delta }}_z$scaling relation, thereby affecting the constraints on Δ_zatℓ= 3000. Allowingz_midandλ_mfpto vary simultaneously, we get spectra consistent with the SPT result (95% CL) up to Δ_z= 12.8 (butA_z> 8 is needed to ensure the end of reionization beforez= 5.5). We show that constraints on the asymmetry require ∼0.1μk²measurement accuracy at multipoles other thanℓ= 3000. Finally, we find that the amplitude and shape of the kSZ spectrum are only weakly sensitive toM_hunder a fixed reionization history and radiation mean free path. 

Abstract It has been claimed that traditional models struggle to explain the tentative detection of the 21 cm absorption trough centered atz∼ 17 measured by the EDGES collaboration. On the other hand, it has been shown that the EDGES results are consistent with an extrapolation of a declining UV luminosity density, following a simple power law of deep Hubble Space Telescope observations of 4 <z< 9 galaxies. We here explore the conditions by which the EDGES detection is consistent with current reionization and post-reionization observations, including the neutral hydrogen fraction atz∼ 6–8, Thomson-scattering optical depth, and ionizing emissivity atz∼ 5. By coupling a physically motivated source model derived from radiative transfer hydrodynamic simulations of reionization to a Markov Chain Monte Carlo sampler, we find that it is entirely possible to reconcile existing high-redshift (cosmic dawn) and low-redshift (reionization) constraints. In particular, we find that high contributions from low-mass halos along with high photon escape fractions are required to simultaneously reproduce cosmic dawn and reionization constraints. Our analysis further confirms that low-mass galaxies produce a flatter emissivity evolution, which leads to an earlier onset of reionization with a gradual and longer duration, resulting in a higher optical depth. While the models dominated by faint galaxies successfully reproduce the measured globally averaged quantities over the first one billion years, they underestimate the late redshift-instantaneous measurements in efficiently star-forming and massive systems. We show that our (simple) physically motivated semianalytical prescription produces results that are consistent with the (sophisticated) state-of-the-artTHESANradiation-magnetohydrodynamic simulation of the reionization. 

Abstract We present UV and Ly α radial surface brightness (SB) profiles of Ly α emitters (LAEs) at z = 2.84 detected with the Hyper Suprime-Cam on the Subaru Telescope. The depth of our data, together with the wide-field coverage including a protocluster, enable us to study the dependence of Ly α halos (LAHs) on various galaxy properties, including Mpc scale environments. UV and Ly α images of 3490 LAEs are extracted, and stacking the images yields SB sensitivity of ∼ 1 × 10 − 20 erg s − 1 cm − 2 arcsec − 2 in Ly α , reaching the expected level of optically thick gas illuminated by the UV background at z ∼ 3. Fitting of the two-component exponential function gives the scale-lengths of 1.56 ± 0.01 and 10.4 ± 0.3 pkpc. Dividing the sample according to their photometric properties, we find that, while the dependence of halo scale-length on environment outside of the protocluster core is not clear, LAEs in the central regions of protoclusters appear to have very large LAHs, which could be caused by combined effects of source overlapping and diffuse Ly α emission from cool intergalactic gas permeating the forming protocluster core irradiated by active members. For the first time, we identify UV halos around bright LAEs that are probably due to a few lower-mass satellite galaxies. Through comparison with recent numerical simulations, we conclude that, while scattered Ly α photons from the host galaxies are dominant, star formation in satellites evidently contributes to LAHs, and that fluorescent Ly α emission may be boosted within protocluster cores at cosmic noon and/or near bright QSOs. 

Abstract Studies of low-redshift galaxy clusters suggest the intracluster medium (ICM) has experienced nongravitational heating during the formation phase of the clusters. Using simple phenomenological heating prescriptions, we simulate the effect of this preheating of the nascent ICM in galaxy protoclusters and examine its effect on Lyαforest tomographic maps. We analyze a series of cosmological zoom-in simulations of protoclusters within the framework of the Lyαtransmission−dark matter (DM) density distribution. We find that the more energy is injected into the proto-ICM atz= 3, the more the distribution at high DM density tilts toward higher Lyαtransmission. This effect has been confirmed in both low-resolution simulations adopting a preheating scheme based on entropy floors, as well as in higher-resolution simulations with another scheme based on energy floors. The evolution of the slope of this distribution is shown to vary with redshift. The methodology developed here can be applied to current and upcoming Lyαforest tomographic survey data to help constrain feedback models in galaxy protoclusters. 

Abstract From a new perspective, we reexamine self-gravity and turbulence jointly, in hopes of understanding the physical basis for one of the most important empirical relations governing clouds in the interstellar medium (ISM), the Larson’s relation relating velocity dispersion (σ_R) to cloud size (R). We report on two key new findings. First, the correct form of the Larson’s relation is, whereα_vis the virial parameter of clouds andσ_pcis the strength of the turbulence, if the turbulence has the Kolmogorov spectrum. Second, the amplitude of Larson’s relation,σ_pc, is not universal, differing by a factor of about 2 between clouds on the Galactic disk and those at the Galactic center, as evidenced by observational data. 

Abstract While most simulations of the epoch of reionization have focused on single-stellar populations in star-forming dwarf galaxies, products of binary evolution are expected to significantly contribute to emissions of hydrogen-ionizing photons. Among these products are stripped stars (or helium stars), which have their envelopes stripped from interactions with binary companions, leaving an exposed helium core. Previous work has suggested these stripped stars can dominate the Lyman Continuum (LyC) photon output of high-redshift, low-luminosity galaxies post-starburst. Other sources of hard radiation in the early universe include zero-metallicity Population iii stars, which may have similar spectral energy distribution (SED) properties to galaxies with radiation dominated by stripped-star emissions. Here, we use four metrics (the power-law exponent over wavelength intervals 240–500 Å, 600–900 Å, and 1200–2000 Å, and the ratio of total luminosity in FUV wavelengths to LyC wavelengths) to compare the SEDs of simulated galaxies with only single-stellar evolution, galaxies containing stripped stars, and galaxies containing Population iii stars, with four different initial mass functions (IMFs). We find that stripped stars significantly alter SEDs in the LyC range of galaxies at the epoch of reionization. SEDs in galaxies with stripped stars have lower power-law indices in the LyC range and lower FUV to LyC luminosity ratios. These differences in SEDs are present at all considered luminosities ( M UV > − 15 , AB system), and are most pronounced for lower-luminosity galaxies. Intrinsic SEDs as well as those with interstellar medium absorption of galaxies with stripped stars and Population iii stars are found to be distinct for all tested Population iii IMFs. 

ABSTRACT Utilizing cosmological hydrodynamic simulations, we quantify the distributions of the dispersion measure (DM) of fast radio bursts (FRBs). We examine the contributions of cold, warm-hot, and hot gas to the total DM. We find that the hot gas component (T > 107K), on average, makes a minor contribution ($$\le 5{{\ \rm per\ cent}}$$) to the overall DM. Cold (T < 105K) and warm-hot (T = 105 − 107K) gas components make comparable contributions to DM for FRBs at z = 1, with the former component making an increasingly larger contribution towards higher redshift. We provide a detailed DM distribution of FRBs at z = 0.25 to z = 2 that may be compared to observations. We also compute the relation between the Compton y parameter and DM, finding a strong correlation, y∝DM4, providing an additional, independent constraint on the nature of the DM of FRBs. 

Abstract The Abundance Matching Box for the Epoch of Reionization (AMBER) is a semi-numerical code for modeling the cosmic dawn. The new algorithm is not based on the excursion set formalism for reionization, but takes the novel approach of calculating the reionization-redshift field $z_{\mathrm{re}}\left(\mathit{x}\right)$assuming that hydrogen gas encountering higher radiation intensity are photoionized earlier. Redshift values are assigned while matching the abundance of ionized mass according to a given mass-weighted ionization fraction ${\overline{x}}_{\mathrm{i}}\left(z\right)$. The code has the unique advantage of allowing users to directly specify the reionization history through the redshift midpointz_mid, duration Δ_z, and asymmetryA_zinput parameters. The reionization process is further controlled through the minimum halo massM_minfor galaxy formation and the radiation mean free pathl_mfpfor radiative transfer. We implement improved methods for constructing density, velocity, halo, and radiation fields, which are essential components for modeling reionization observables. We compare AMBER with two other semi-numerical methods and find that our code more accurately reproduces the results from radiation-hydrodynamic simulations. The parallelized code is over four orders of magnitude faster than radiative transfer simulations and will efficiently enable large-volume models, full-sky mock observations, and parameter-space studies. AMBER will be made publicly available to facilitate and transform studies of the Epoch of Reionization. 

Streams of intergalactic gas enriched by previous star formation were observed spiraling toward a massive galaxy.