The Mass Spectrum of the First Stars

Abstract

We perform cosmological hydrodynamics simulations with non-equilibrium primordial chemistry to obtain 59 minihalos that host first stars. The obtained minihalos are used as initial conditions of local three dimensional radiation hydrodynamics simulations to investigate the formation of the first stars. We find two-thirds of the minihalos host multiple stars, while the rest of them have single stars. The mass of the stars found in our simulations are in the range of 1M ⊙ M 300M ⊙ , peaking at several×10M ⊙ . Most of the very massive stars of 140M ⊙ are born as single stars, although not all of the single stars are very massive. We also find a few stars of 1M ⊙ that are kicked by the gravitational three body interactions to the position distant from the center of mass. The frequency that a star forming minihalo contains a binary system is ∼ 50%. We also investigate the abundance pattern of the stellar remnants by summing up the contributions from the first stars in the simulations. Consequently, the pattern is compatible with that of the low metallicity Damped Lyman−α systems or the Extremely Metal Poor (EMP) stars , if the mass spectrum obtained in our experiment is shifted to the low mass side by 0.2 dex. If we consider the case that an EMP star is born in the remnant of the individual minihalo without mixing with others, the chemical signature of the pair instability supernova is more prominent, because most of them are born as single stars. Subject headings: early Universe-radiative transfer -first stars-metal poor stars

Primordial star formation under the influence of far ultraviolet radiation: 1540 cosmological haloes and the stellar mass distribution

“…A wide range of stellar masses is obtained, extending from 10 to 1600 M⊙, which suggests a great diversity of primordial stars. Despite several physical effects that are not directly realized in 2D simulations, e.g., disc fragmentation and stellar multiplicity, such diversity is consistently reported by other studies including recent 3D simulations (Susa et al 2014). 1 Interestingly, we find cor-1 We adopt the so-called alpha-viscosity whose value is calibrated with respect to the results of recent 3D simulations (see relations between the final stellar masses and the physical properties of star-forming clouds, M * = 100 M⊙ Ṁ Jeans 2.8 × 10 −3 M⊙ yr −1…”

“…This could lead to the formation of multiple stellar systems rather than a single star in each mini-halo. In this case, the available gas in the envelope is divided among multiple protostars, so that the stars in such a multiple system could have relatively lower masses than in the case of a single star (e.g., Peters et al 2010;Susa et al 2014). However, there is an opposite effect; a large fraction of the protostars could rapidly migrate inward due to gravitational torque, resulting in frequent stellar mergers at the cloud centre (e.g., Greif et al 2012;Vorobyov et al 2013).…”

Gamma-Ray Bursts and Population III Stars

“…However, first attempts to carry out the radiation-hydrodynamical calculations required to treat the late accretion phase, where protostellar feedback tends to limit further infall, have confirmed the basic prediction: the first stars were typically massive, with masses of a few ∼ 10M ⊙ , although rarely very massive (> 100M ⊙ ), as previously thought, forming as a member of small multiple systems (McKee & Tan 2008;Hosokawa et al 2011;Stacy et al 2012). There are indications, though, that the Pop III mass could occasionally grow to > 300M ⊙ , in cases of unusually weak protostellar feedback (Hirano et al 2014;Susa et al 2014).…”

The Sejong Open Cluster Survey (Sos). Iv. The Young Open Clusters NGC 1624 and NGC 1931

“…The temperature of a molecular cloud may therefore be higher in the lowmetallicity environment because radiative cooling by metallic ions will be lower (Caramazza et al 2012). Furthermore, there is a relation between the mass accretion rate of a star and the temperature of a cloud (M Ṫ Susa et al 2014). As a result, high-mass stars may be formed advantageously in such a low-metallicity environment, rather than active lowmass star formation.…”