Three-Dimensional Modelling of Ionized Gas. I. Did very massive stars of different metallicities drive the second cosmic reionization?

Abstract

The first generation of stars that formed directly from the primordial gas played a crucial role in the early phase of the reionization of the universe. Because of the short lifetimes of these stars the metals produced in their cores were quickly returned to the environment, from which early PopII stars with a different initial mass function and different SEDs were formed, already much earlier than the time at which the universe became completely reionized at a redshift of z~6. Using a state-of-the-art model atmosphere code we calculate realistic SEDs of very massive stars (VMSs) of different metallicities to serve as input for the 3-dimensional multi-frequency radiative transfer code we have developed to simulate the temporal evolution of the ionization of the inhomogeneous interstellar and intergalactic medium, using multiple stellar clusters as sources of ionizing radiation. Our tool handles distributions of numerous radiative sources characterized by high resolution synthetic SEDs, and yields occupation numbers of the required energy levels of the most important elements which are treated in NLTE consistently with the 3d radiative transfer. We further demonstrate that the increasing metallicity of the radiative sources in the transition from PopIII stars to PopII stars has a strong impact on the hardness of the emitted spectrum, and hence on the reionization history of helium. A top-heavy stellar mass distribution characterized by VMSs forming in chemically evolved clusters of high core mass density may not only provide the progenitors of intermediate-mass and supermassive black holes (SMBHs), but also play an important role for the reionization of HeII. The number of VMSs required to reionize HeII by a redshift of z~2.5 is astonishingly close to the number of VMSs required to explain galactic SMBHs if one assumes that these have been formed by mergers of smaller black holes.

Accepted by A&A. 23 pages, 26 figures

References in corpus (13)

• Observational constraints on Cosmic Reionization
• The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit
• The morphology of HII regions during reionization
• HeII Reionization and its Effect on the IGM
• Radiative transfer simulations of cosmic reionization I: methodology and initial results
• Cosmological Radiative Transfer Codes Comparison Project I: The Static Density Field Tests
• The Initial Mass Function of the Massive Star-forming Region NGC 3603 from Near-Infrared Adaptive Optics observations
• How Very Massive Metal Free Stars Start Cosmological Reionization
• Relative Role of Stars and Quasars in Cosmic Reionization
• An implementation of radiative transfer in the cosmological simulation code GADGET
• Evolution of Collisionally Merged Massive Stars
• Spitzer Observations of M83 and the Hot Star, H II Region Connection
• Probing the first galaxies with the SKA

Cited by in corpus (6)

• 3D radiative transfer: Continuum and line scattering in non-spherical winds from OB stars
• Numerical Models for the Diffuse Ionized Gas in Galaxies. II. Three-dimensional radiative transfer in inhomogeneous interstellar structures as a tool for analyzing the diffuse ionized gas
• Three-dimensional modeling of ionized gas. II. Spectral energy distributions of massive and very massive stars in stationary and time-dependent modeling of the ionization of metals in HII regions
• Non-LTE models for synthetic spectra of type Ia supernovae. III. An accelerated lambda iteration procedure for the mutual interaction of strong spectral lines in SN Ia models with and without energy deposition
• Radiative transfer of 21-cm line through ionised cavities in an expanding universe
• Non-LTE models for synthetic spectra of type Ia supernovae. IV. A modified Feautrier scheme for opacity-sampled pseudo-continua at high expansion velocities and application to synthetic SN Ia spectra