Related papers: Intergalactic heating by Lyman-alpha photons inclu…
The reionization of helium is thought to occur at $2.5\lesssim z\lesssim4$, marking the last phase transition and final global heating event of the intergalactic medium (IGM). Since it is driven by rare quasars, helium reionization should…
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…
21 cm cosmology, the statistical observation of the high redshift universe using the hyperfine transition of neutral hydrogen, has the potential to revolutionize our understanding of cosmology and the astrophysical processes that underlie…
I use cosmological simulations that incorporate a physically motivated approximation to three-dimensional radiative transfer that recovers correct asymptotic ionization front propagation speeds for some cosmologically relevant density…
We develop an efficient method to study the effects of reionization history on the temperature-density relation of the intergalactic medium in the low density limit (overdensity less than 5). It is applied to the study of photo-reionization…
The evolution of the temperature in the intergalactic medium is related to the reionization of hydrogen and helium, and has important consequences for our understanding of the Lya forest and of galaxy formation in gravitational models of…
The cosmological 21-cm signal from neutral hydrogen, which is considered as a promising tool, is being used to observe and study the cosmic dawn (CD) and epoch of reionization (EoR). A significant part of this thesis focuses on the…
The timing and duration of the reionization epoch is crucial to the emergence and evolution of structure in the universe. The relative roles that star-forming galaxies, active galactic nuclei and quasars play in contributing to the…
We compute the corrections to the cosmological hydrogen recombination history due to delayed feedback of Lyman-series photons and the escape in the Lyman-continuum. The former process is expected to slightly delay recombination, while the…
The redshifted 21cm signal from the Cosmic Dawn is expected to provide unprecedented insights into early Universe astrophysics and cosmology. Here we explore how dark matter can heat the intergalactic medium before the first galaxies,…
[ABRIDGED] The cosmological 21cm signal is set to become the most powerful probe of the early Universe, with first generation interferometers aiming to make statistical detections of reionization. There is increasing interest also in the…
It has been realised only recently that TeV emission from blazars can significantly heat the intergalactic medium (IGM) by pair-producing high-energy electrons and positrons, which in turn excite vigorous plasma instabilities, leading to a…
As increasingly precise information about the spectrum of the cosmic microwave background fluctuations is gathered with balloon and satellite experiments, interest has grown in foreground sources of opacity affecting these observations. One…
Observations of resolved HeII Lyman alpha absorption in spectra of two QSO's suggest that the epoch of helium ionization occurred at z~3. Proximity zones in the spectra of the quasars (z=3.18, 3.285) at 304 A resemble Stromgren spheres,…
Reionization is a process whereby hydrogen (and helium) in the Universe is ionized by the radiation from first luminous sources. Theoretically, the importance of the reionization lies in its close coupling with the formation of first cosmic…
The 21-cm forest is a promising probe of the Epoch of Reionization. The local state of the intergalactic medium (IGM) is encoded in the spectrum of a background source (radio-loud quasars or gamma ray burst afterglow) by absorption at the…
The cosmic 21-cm signal is a promising probe of the early Universe, owing to its sensitivity to the thermal state of the neutral intergalactic medium (IGM) and properties of the first luminous sources. Here, we constrain the 21-cm signal…
The recent measurement by WMAP of a large electron scattering optical depth tau_e = 0.17 +- 0.04 is consistent with a simple model of reionization in which the intergalactic medium (IGM) is ionized at redshift z ~ 15, and remains highly…
Cosmic-ray and X-ray heating are derived from the electron energy loss calculations of Dalgarno, Yan and Liu for hydrogen-helium gas mixtures. These authors treated the heating from elastic scattering and collisional de-excitation of…
The process of heating and reionization of the Universe at high redshift links small scale structures/galaxy formation and large scale inter-galactic medium properties. Even if the first one is difficult to observe, an observation window is…