Metal Pollution of Low-Mass Population III Stars through Accretion of Interstellar Objects like `Oumuamua

Abstract

We calculate accretion mass of interstellar objects (ISOs) like `Oumuamua onto low-mass population III stars (Pop.~III survivors), and estimate surface pollution of Pop.~III survivors. An ISO number density estimated from the discovery of `Oumuamua is so high ($\sim 0.2$~au${}^{-3}$) that Pop.~III survivors have chances at colliding with ISOs $\gtrsim 10^5$ times per $1$~Gyr. `Oumuamua itself would be sublimated near Pop.~III survivors, since it has small size, $\sim 100$~m. However, ISOs with size $\gtrsim 3$~km would reach the Pop.~III survivor surfaces. Supposing an ISO cumulative number density with size larger than $D$ is $n\propto D^{-\alpha }$, Pop.~III survivors can accrete ISO mass $\gtrsim 10^{-16}{M}_{\odot }$, or ISO iron mass $\gtrsim 10^{-17}{M}_{\odot }$, if $\alpha <4$. This iron mass is larger than the accretion mass of interstellar medium (ISM) by several orders of magnitude. Taking into account material mixing in a convection zone of Pop.~III survivors, we obtain their surface pollution is typically [Fe/H] $\lesssim -8$ in most cases, however the surface pollution of Pop.~III survivors with $0.8M_{\odot }$ can be [Fe/H] $\gtrsim -6$ because of the very shallow convective layer. If we apply to Pop.III survivors located at the Galactocentric distance of 8 kpc, the dependence of the metal pollustion is as follows. If $\alpha >4$, Pop.~III survivors have no chance at colliding with ISOs with $D\gtrsim 3$~km, and keep metal-free. If $3<\alpha <4$, Pop.~III survivors would be most polluted by ISOs up to [Fe/H] $\sim -7$. If $\alpha <3$ up to $D\sim 10$~km, Pop.~III survivors could hide in metal-poor stars so far discovered. Pop.~III survivors would be more polluted with decreasing the Galactocentric distance. Although the metal pollution depends on $\alpha$ and the Galactocentric distance, we first show the importance of ISOs for the metal pollution of Pop.~III survivors.

6 pages, 3 figures, accepted for publication in PASJ

References in corpus (14)

• An absorption profile centred at 78 megahertz in the sky-averaged spectrum
• Possible interaction between baryons and dark-matter particles revealed by the first stars
• Protostar Formation in the Early Universe
• Primordial Star Formation under the Influence of Far Ultraviolet Radiation: 1540 Cosmological Halos and the Stellar Mass Distribution
• The Mass Spectrum of the First Stars
• TOPoS: II. On the bimodality of carbon abundance in CEMP stars. Implications on the early chemical evolution of galaxies
• Interstellar Interlopers: Number Density and Origins of 'Oumuamua-like Objects
• The AMBRE Project: chemical evolution models for the Milky Way thick and thin discs
• The origin of interstellar asteroidal objects like 1I/2017 U1 'Oumuamua
• Conditions for the Formation of First-Star Binaries
• The Spatial Distribution of the Galactic First Stars I: High-Resolution N-body Approach
• The Albedo Distribution of Near Earth Asteroids
• Probing Planets in Extragalactic Galaxies Using Quasar Microlensing
• Blocking metal accretion onto population III stars by stellar wind

Cited by in corpus (11)

• Merger rate density of Population III binary black holes below, above, and in the pair-instability mass gap
• Fitting formulae for evolution tracks of massive stars under extreme metal poor environments for population synthesis calculations and star cluster simulations
• Fragmentation induced starvation in Population III star formation: a resolution study
• An Ultra Metal-poor Star Near the Hydrogen-burning Limit
• Three-Dimensional Simulation of Double-Detonations in the Double-Degenerate Model for Type Ia Supernovae and Interaction of Ejecta with a Surviving White Dwarf Companion
• Observational constraints on the survival of pristine stars
• Fingerprint of the first stars: multi-enriched extremely metal-poor stars in the TOPoS survey
• A hypothesis for the rapid formation of planets
• Coronae of Zero/Low-Metal Low-Mass Stars
• Effect of interstellar objects on metallicity of low-mass first stars formed in a cosmological model
• Coronal Properties of Low-mass Population III Stars and the Radiative Feedback in the Early Universe