Formation of GW190521 via Gas Accretion onto Population III Stellar Black Hole Remnants Born in High-redshift Minihalos
Formation of GW190521 via Gas Accretion onto Population III Stellar Black Hole Remnants Born in High-redshift Minihalos
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DOI：
10.3847/2041-8213/abc253
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发表时间：
2020-09
期刊：
影响因子：
--
通讯作者：
M. Safarzadeh;Z. Haiman
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文献类型：
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作者：
M. Safarzadeh;Z. Haiman
最近的引力波合并事件GW190521挑战了我们对恒星质量黑洞(BH)形成的理解。推测初级和次级BHS都落在对不稳定性(PI)质量间隙内。在这里，我们提出，这种双星的形成是通过气体吸积在高红移(z>；10)迷你晕中诞生的族III恒星的BH残留物上实现的。一旦母晕增长到原子冷却极限，即使是在晕致密中心区域短暂的气体吸积，也可以使粒子III剩余的BHS质量增加到PI极限以上。从一个初始质量为O(100M)⊙的二元黑洞开始，我们发现它只需要在原子冷却晕的内部几个部分花费大约100Myr就可以共生大约50M⊙的物质，类似于一个类似GW190521的系统。双星下沉到其母晕密集内区的动力摩擦时间刻度与增加其质量超过PI极限所需的吸积时间刻度相当或更短。一旦进入光晕的核心，双星就可以进入超爱丁顿吸积阶段，在这个阶段，只需要几千年的时间就可以通过吸积超过pI极限。甚至更大质量的BBH可以通过这个通道形成，并可以被具有改进的低频灵敏度的探测器探测到。单种群III的BH残留物也会通过吸积生长，以后可能会动态形成双星。只有人口III的几个百分点的BH残留物可能足以与从GW190521的GW190521推断的大规模BBH合并的速度相匹配。
The recent gravitational-wave merger event, GW190521, has challenged our understanding of stellar-mass black hole (BH) formation. The primary and secondary BHs are both inferred to fall inside the pair-instability (PI) mass gap. Here we propose that the formation of such binaries is possible through gas accretion onto the BH remnants of Population III stars born in high-redshift (z > 10) minihalos. Once the parent halo has grown to the atomic-cooling limit, even brief episodes of gas accretion in the dense central regions of the halo can increase the masses of Population III remnant BHs above the PI limit. Starting with a binary black hole (BBH) with an initial mass of O(100) M ⊙ we find that it would only need to spend about 100 Myr in the inner few parsecs of an atomic-cooling halo to accrete about 50 M ⊙ of material and resemble a system similar to GW190521. The dynamical friction timescale for the binary to sink to the dense inner region of its parent halo is comparable or shorter than the accretion timescale required to increase their mass above the PI limit. Once in the core of the halo, the binary can enter a phase of hyper-Eddington accretion, where it would only take a few thousand years to exceed the PI limit through accretion. Even more massive BBHs could form through this channel, and be detectable by detectors with improved low-frequency sensitivity. Single Population III BH remnants would also grow through accretion and could later form binaries dynamically. As little as a few percent of Population III BH remnants may be sufficient to match the rate of massive BBH mergers inferred from GW190521 of .