低质量星族III星吸积的抑制
Suppression of accretion onto low-mass Population III stars
摘要：
最近的理论工作表明，相当一部分的人口（流行）III星可能有足够低的质量，他们生存到今天，我们认为的作用，吸积的金属富集气体可能已经改变了他们的表面成分，从而伪装成流行II星。我们证明，如果弱，太阳风发射的低质量的Pop III星形成的银河系的暗物质晕的祖先，那么这样的恒星很可能避免显着富集通过吸积的物质从星际介质。我们发现，在早期吸积是很容易防止的，如果恒星从中央地区的晕，他们形成，无论是通过动态相互作用与更大的波普III星，或通过暴力松弛晕合并。虽然吸积仍然可能发生在通过足够密集的分子云在以后的时间，我们发现，这样的通道的概率一般很低（< 0.1），假设恒星的速度的顺序的最大圆周速度的主机晕和帐户的轨道衰变合并晕。反过来，由于吸积到速度更高的恒星上所需的气体密度更高，我们发现在z > 10时形成的Pop III恒星子集的吸积概率更低（~ 0.01），它们比在较低红移时形成的恒星更快地融入大质量晕。虽然没有先验的理由假设低质量的Pop III恒星没有类似太阳的风，但没有它们，通过吸积的表面富集可能是不可避免的。我们简要讨论了我们的研究结果对恒星考古学的影响。
英文摘要：
Motivated by recent theoretical work suggesting that a substantial fraction of Population (Pop) III stars may have had masses low enough for them to survive to the present day, we consider the role that the accretion of metal-enriched gas may have had in altering their surface composition, thereby disguising them as Pop II stars. We demonstrate that if weak, Solar-like winds are launched from low-mass Pop III stars formed in the progenitors of the dark matter halo of the Galaxy, then such stars are likely to avoid significant enrichment via accretion of material from the interstellar medium. We find that at early times accretion is easily prevented if the stars are ejected from the central regions of the haloes in which they form, either by dynamical interactions with more massive Pop III stars, or by violent relaxation during halo mergers. While accretion may still take place during passage through sufficiently dense molecular clouds at later times, we find that the probability of such a passage is generally low (< 0.1), assuming that stars have velocities of order the maximum circular velocity of their host haloes and accounting for the orbital decay of merging haloes. In turn, due to the higher gas density required for accretion onto stars with higher velocities, we find an even lower probability of accretion (~ 0.01) for the subset of Pop III stars formed at z > 10, which are more quickly incorporated into massive haloes than stars formed at lower redshift. While there is no a priori reason to assume that low-mass Pop III stars do not have Solar-like winds, without them surface enrichment via accretion is likely to be inevitable. We briefly discuss the implications that our results hold for stellar archaeology.
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