Abstract:
We investigate metal pollution onto the surface of low-mass first stars (Pop. III survivors) via interstellar objects (ISOs) floating in the Galactic interstellar medium. Only recently, Tanikawa et al. analytically estimated how much metal should collide to an orbiting Pop. III survivor encouraged by the recent discovery of ’Oumuamua and suggested that ISOs are the most dominant contributor of metal enrichment of Pop. III survivors. We consider a distribution of ISOs in the Galactic disc again and calculate the ISO accretion rate considering the more realistic orbits of Pop. III survivors’ using a high-resolution cosmological N-body simulation that resolves dark matter minihalos. As a result, Pop. III survivors located at solar neighborhood have a number of chances of ISO(> 100 m) collisions, typically 5 million times in the last 5 Gyr, which is one order of magnitude greater than estimated in the previous study. Metal-poor stars so far discovered are possible to be metal-free Pop. III stars on birth.