不只是恒星风：为何模型发现双黑洞形成具有金属丰度依赖性，而双中子星形成则没有
Not just winds: why models find binary black hole formation is metallicity dependent, while binary neutron star formation is not
AI总结：
本研究探究双致密天体形成的金属丰度依赖性成因，发现双黑洞形成效率的金属丰度依赖源于不同形成通道的差异，双中子星因仅经公共包层通道形成而无该依赖性，引力波观测可提供约束。
摘要：
无论是详细星族研究还是快速星族研究都预测，双黑洞（BHBH）的形成效率在低金属丰度环境下比高金属丰度环境下高出数个数量级，而双中子星（NSNS）的形成效率随金属丰度变化基本保持平稳，黑洞-中子星并合（BHNS）则表现出介于两者之间的行为。这一发现是将双致密天体用作低金属丰度恒星形成示踪剂、作为光谱标准汽笛以及计算并合率的关键输入。然而，现有文献对这些趋势给出了多种（有时相互矛盾的）解释。我们研究了双致密天体形成的金属丰度依赖性的主导成因。我们发现，低金属丰度下的BHBH形成效率由初始条件分布决定，传统模拟表明，在质量足以形成黑洞的相互作用双星系统中，约有八分之一会最终形成并合的BHBH。我们进一步发现，金属丰度在双致密天体形成中的重要性取决于形成通道。稳定质量转移通道和化学均匀演化通道在高金属丰度下的形成效率主要因恒星半径的变化而降低，而公共包层通道则主要受恒星风与按质量缩放的诞生冲力的共同作用影响。过时的红巨星风模型会加剧后一种效应，这表明BHBH形成的金属丰度依赖性可能比之前假设的要弱得多。NSNS的形成效率之所以与金属丰度无关，是因为它们仅通过公共包层通道形成，且其诞生冲力被假设与质量不相关。即将到来的引力波（GW）观测将为这些发现提供宝贵的约束。
英文摘要：
Both detailed and rapid population studies alike predict that binary black hole (BHBH) formation is orders of magnitude more efficient at low metallicity than high metallicity, while binary neutron star (NSNS) formation remains mostly flat with metallicity, and black hole-neutron star (BHNS) mergers show intermediate behavior. This finding is a key input to employ double compact objects as tracers of low-metallicity star formation, as spectral sirens, and for merger rate calculations. Yet, the literature offers various (sometimes contradicting) explanations for these trends. We investigate the dominant cause for the metallicity dependence of double compact object formation. We find that the BHBH formation efficiency at low metallicity is set by initial condition distributions, and conventional simulations suggest that about \textit{one in eight interacting binary systems} with sufficient mass to form black holes will lead to a merging BHBH. We further find that the significance of metallicities in double compact object formation is a question of formation channel. The stable mass transfer and chemically homogeneous evolution channels mainly diminish at high metallicities due to changes in stellar radii, while the common envelope channel is primarily impacted by the combined effects of stellar winds and mass-scaled natal kicks. Outdated giant wind prescriptions exacerbate the latter effect, suggesting BHBH formation may be much less metallicity dependent than previously assumed. NSNS formation efficiency remains metallicity independent as they form exclusively through the common envelope channel, with natal kicks that are assumed uncorrelated with mass. Forthcoming GW observations will provide valuable constraints on these findings.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
