相关论文: Critical Metallicities for Second-Generation Stars
We simulate the formation of a metal-poor (10^-2 Zsun) stellar cluster in one of the first galaxies to form in the early Universe, specifically a high-redshift atomic cooling halo (z~14). This is the first calculation that resolves the…
A brief review concludes that there is now good overall agreement between theoretical estimates of the energy associated with the production of the observed metal content of the Universe and the observed extragalactic background light. In…
A rapidly growing body of observational results suggests that planet formation takes place preferentially at high metallicity. In the core accretion model of planet formation this is expected because heavy elements are needed to form the…
Star formation is regulated through a variety of feedback processes. In this study, we treat feedback by metal injection and a UV background as well as by X-ray irradiation. Our aim is to investigate whether star formation is significantly…
The stellar metallicity is a direct measure of the amount of metals present in a galaxy, as a large part of the metals lie in its stars. In this paper we investigate new stellar metallicity indicators suitable for high-z galaxies studying…
The cosmic-ray ionization rate ($\zeta_2$) is one of the key parameters in star formation, since it regulates the chemical and dynamical evolution of molecular clouds by ionizing molecules and determining the coupling between the magnetic…
First stars play crucial roles in development of the universe, influencing events like cosmic reionization and the chemical enrichment. While first stars are conventionally thought to form at around $z \sim 20-30$ in the standard $\Lambda$…
We show that gaseous \HI disks of primordial composition irradiated by an external radiation field can develop a multiphase medium with temperatures between 10^2 and 10^4 K due to the formation of molecular hydrogen. For a given \HI column…
The early Universe had a chemical composition consisting of hydrogen, helium and traces of lithium1, almost all other elements were created in stars and supernovae. The mass fraction, Z, of elements more massive than helium, is called…
We present a simulation of the formation of the earliest Population II stars, starting from cosmological initial conditions and ending when metals created in the first supernovae are incorporated into a collapsing gas-cloud. This occurs…
The contraction processes of metal-free molecular clouds of starlike mass (or cloud cores) are investigated. We calculate radiative transfer of the H_2 lines and examine quasi-static contraction with radiative cooling. Comparing two…
The tight relation of star formation with molecular gas indicated by observations and assumed in recent models implies that the efficiency with which galaxies convert their gas into stars depends on gas metallicity. This is because the…
We study the impact of molecular (${\rm H_2}$) and atomic (HI) hydrogen cooling on the galaxy formation threshold. We calculate the fraction of dark matter (DM) halos that exceeds a critical mass required for star formation,…
The minimum initial mass required for a star to explode as an Fe core collapse supernova, typically denoted $M_\text{mas}$, is an important quantity in stellar evolution because it defines the border between intermediate mass and massive…
Performing 1D hydrodynamical calculations coupled with non-equilibrium processes for H2 formation, we pursue the thermal and dynamical evolution of filamentary primordial clouds and attempt to make an estimate on the mass of population III…
Dust in protoplanetary disks is recognized as the building blocks of planets. In the core accretion scenario, the abundance of dust in disks (or metallicity) is crucial for forming cores of gas giants. We present our recent progress on the…
High redshift quasars at z>6 have masses up to ~$10^9$ M$_\odot$. One of the pathways to their formation includes direct collapse of gas, forming a supermassive star, precursor of the black hole seed. The conditions for direct collapse are…
We report the statistical properties of stars and brown dwarfs obtained from three radiation hydrodynamical simulations of star cluster formation with metallicities of 1, 1/10 and 1/100 of the solar value. The star-forming clouds are…
The young $\sigma$-Orionis cluster is an important location for understanding the formation and evolution of stars, brown dwarfs, and planetary-mass objects. Its metallicity, although being a fundamental parameter, has not been well…
The metallicities implied by collisionally excited lines (CELs) of heavy elements in H II regions are systematically lower than those implied by recombination lines (RLs) by factors ~2, introducing uncertainties of the same order in the…