相关论文: Re-ionizing the Universe without Stars

We determine the abundance of i'-band drop-outs in the HST/ACS GOODS surveys and the Hubble Ultra Deep Field (UDF). The majority of these sources are likely to be z~6 galaxies whose flux decrement arises from Lyman-alpha absorption. We have…

Absorption spectra of high redshift quasars suggest that the reionisation of cosmic hydrogen was complete near z~6. The dominant sources of ionising photons responsible for this reionisation are generally thought to be stars and quasars. In…

Cosmological structure formation simulations of ultralight axion-like dark matter have shown that an axion star forms at the center of every dark matter halo in the Universe. These axion stars would then form in large numbers during the…

We compare the available catalogs of $z\approx6$ galaxies in the Hubble Ultra-Deep Field (UDF) and in the Great Observatories Origins Deep Survey (GOODS) with the expected properties of the sources of cosmological reionization from our…

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…

Gas rich sub-galactic halos with mass Mt <= 10^7.5 Msun, while incapable of forming stars due to lack of adequate coolants, contain a large fraction of baryonic mass at cosmological reionization. We show that the reionization of the…

The transition between the nearly smooth initial state of the Universe and its clumpy state today occurred during the epoch when the first stars and low-luminosity quasars formed. For Cold Dark Matter cosmologies, the radiation produced by…

Galaxies forming in low-mass halos are thought to be primarily responsible for reionizing the Universe during the first billion years after the Big Bang. Yet, these halos are extremely inefficient at forming stars in the nearby Universe. In…

We examine the constraints on high-redshift star formation, ultraviolet and X-ray pre-ionization, and the epoch of reionization at redshift z_r, inferred from the recent WMAP-5 measurement, tau_e = 0.084 +/- 0.016, of the electron…

Early results from the JWST observations have reported a surprisingly high number of UV-bright galaxies at $z \geq 10$, which appears to challenge the theoretical predictions from standard galaxy formation models in the $\Lambda$CDM…

The rest-frame UV emission from massive stars contains a wealth of information about the physical nature and conditions of star formation in galaxies. Using studies of the rest-frame UV, the past decade has witnessed the beginning of…

A population of early star-forming galaxies is the leading candidate for the re-ionization of the universe. It is still unclear what conditions and physical processes would enable a significant fraction of the ionizing photons to escape…

We use high resolution N-body/gasdynamical simulations to investigate the effects of a photoionizing UV background on the assembly of disk galaxies in hierarchically clustering universes. We focus on the mass and rotational properties of…

Formation of massive stars by accretion requires a high accretion rate of > 10^-4 M_sun/yr to overcome the radiation pressure barrier of the forming stars. Here, we study evolution of protostars accreting at such high rates, by solving the…

Using reconstructed galaxy star formation histories, we calculate the instantaneous efficiency of galaxy star formation (i.e., the star formation rate divided by the baryon accretion rate) from $z=8$ to the present day. This efficiency…

One possible scenario for the formation of massive black holes (BHs) in the early Universe is from the direct collapse of primordial gas in atomic-cooling dark matter haloes in which the gas is unable to cool efficiently via molecular…

We investigate the implications of the intergalactic opacity for the evolution of the cosmic UV luminosity density and its sources. Our main constraint is our measurement of the Lya forest opacity at redshifts 2<z<4.2 from 86…

The presence of ultra-high energy cosmic rays in the universe in the pre-ionization epoch enhances significantly H$_2$ kinetics in virialized halos. It results in more efficient radiative cooling and decreases the lower mass limit of the…

We present the first large-scale radiative transfer simulations of cosmic reionization, in a simulation volume of (100/h Mpc)^3, while at the same time capturing the dwarf galaxies which are primarily responsible for reionization. We…

Although empirical evidence indicates that that the universe's gas had become ionized by redshift z ~ 6, the mechanism by which this transition occurred remains unclear. In this article, we explore the possibility that dark matter…