Related papers: Ionization Front Instabilities in Primordial H II …
The nature of the sources powering nebular HeII emission in star-forming galaxies remains debated, and various types of objects have been considered, including Wolf-Rayet stars, X-ray binaries, and Population III stars. Modern X-ray…
Medium-resolution spectra from 3650 angstroms to 10,000 angstroms are presented for 96 giant H II regions distributed in 20 spiral galaxies. We have calculated two separate grids of photoionization models, adopting single-star atmospheres…
The first generation of protogalaxies likely formed out of primordial gas via H2-cooling in cosmological minihalos with virial temperatures of a few 1000K. However, their abundance is likely to have been severely limited by feedback…
There has been considerable theoretical debate over whether photoionization and supernova feedback from the first Population III stars facilitate or suppress the formation of the next generation of stars. We present results from an Eulerian…
Within collapsing protogalaxies, thermal instability leads to the formation of a population of cool fragments which are confined by the pressure of a residual hot background medium. The critical mass required for the cold clouds to become…
(Abridged) We present the results of three-dimensional radiation-hydrodynamics simulations of the formation and evolution of early HII/HeIII regions around the first stars. Cooling (by H2 and HD) and recollapse of the gas in the relic HII…
The first massive stars may influence the formation of second-generation stars, in part by their metal enrichment of the surrounding gas. We investigate the "critical metallicity", defined as the the value, Z_crit, at which primordial gas…
We simulate the ionization environment of z ~ 20 luminous objects formed within the framework of the current CDM cosmology and compute their UV escape fraction. These objects are likely single very massive stars that are copious UV…
We study the effect of starlight from the first stars on the ability of other minihaloes in their neighborhood to form additional stars. The question of what the dynamical consequences were for these target minihaloes, of their exposure to…
Molecular outflows contributing to the matter cycle of star forming galaxies are now observed in small and large systems at low and high redshift. Their physical origin is still unclear. In most theoretical studies only warm ionised/neutral…
Recent results by the WMAP satellite suggest that the intergalactic medium was significantly reionized at redshifts as high as z~17. At this early epoch, the first ionizing sources likely appeared in the shallow potential wells of…
We study the evolution of gas in HII regions around the first stars after the death of the exciting stars. If the first star in a small halo dies without supernova (SN), subsequent star formation is possible in the same halo. We thus…
In the primordial universe, low mass structures with virial temperatures less than 10$^{4}$ K were unable to cool by atomic line transitions, leading to a strong suppression of star formation. On the other hand, these "minihalos" were…
We study the H2 photodissociation regions around OB stars in primordial gas clouds whose virial temperatures are between a few hundred and a few thousand Kelvin. In such small objects, a single O star can photodissociate a mass equal to…
Observations of nearby galaxies have firmly established, over a broad range of galactic environments and metallicities, that star formation occurs exclusively in the molecular phase of the interstellar medium (ISM). Theoretical models show…
We describe the first three-dimensional simulation of the gravitational collapse of a massive, rotating molecular cloud that includes heating by both non-ionizing and ionizing radiation. We find that as the first protostars gain sufficient…
H2 formation in metal-free gas occurs via the intermediate H- or H2+ ions. Destruction of these ions by photodissociation therefore serves to suppress H2 formation. In this paper, I highlight the fact that several processes that occur in…
We suggest that Bipolar H{\sc ii} Regions may be the aftermath of collisions between clouds. Such a collision will produce a shock-compressed layer, and a star cluster can then condense out of the dense gas near the centre of the layer. If…
We study the influence of gas metallicity, turbulence, and non-equilibrium chemistry on the evolution of the two-phase interstellar medium (warm and cold atomic phases), and thereby constrain the initial conditions for star formation…
The escape of ionizing radiation from galaxies plays a critical role in the evolution of gas in galaxies, and the heating and ionization history of the intergalactic medium. We present semi-analytic calculations of the escape fraction of…