原初黑洞丰度的预测：来自SMILE VLBI毫透镜样本的结果
Predictions on the abundance of primordial black holes: results from the SMILE VLBI milli-lensing sample
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中文总结 AI 辅助
本研究利用SMILE样本约5000个射电源，预测原初黑洞暗物质丰度上限，在无毫透镜事件时95%上限为0.12%，较以往严格一个数量级，并强调候选体确认的重要性。
中文摘要 AI 辅助
在早期宇宙中形成的原初黑洞（PBHs）是一个动机良好的暗物质候选体。然而，它们在中间到高质量范围（$10^6$-$10^9\\,M_\odot$）内的丰度仍然相对较少受到约束。在这一质量范围内，对应的爱因斯坦半径处于毫角秒尺度，这使得甚长基线干涉测量（VLBI）通过致密射电源的毫透镜效应成为最直接的观测探针。在本文中，我们利用包含约5000个平谱致密射电源的大型SMILE样本，对PBH暗物质丰度（$f_{\rm PBH}$）进行了预测。在乐观的观测条件下（角分辨率为$1.5\\,\mathrm{mas}$，最大图像分离为$100\\,\mathrm{mas}$，最大可探测流量比为$40$），假设没有确认任何毫透镜事件，我们得到在中间到高质量范围内$f_{\rm PBH}\lesssim0.12\\%$的预计95%上限，这将比之前的VLBI毫透镜限制严格约一个数量级。更宽的对数正态质量函数相应地产生较弱的预计限制。将光学深度推广以考虑放大偏差和有限核心可分辨性，这些预计限制仅改变约$5\\%$。此外，我们表明预计限制对少量确认事件高度敏感，即即使一个确认的毫透镜事件也会将预计上限放宽到$0.20\\%$，这凸显了在SMILE样本中进行稳健候选体确认的关键重要性。最后，在乐观的重子吸积情景下，PBH质量增长在VLBI敏感质量范围内改变预计限制不超过$\lesssim 1\\%$，证实了我们结果的稳健性。
英文摘要
Primordial black holes (PBHs) formed in the early universe represent a well-motivated dark matter candidate. However, their abundance in the intermediate-to-high mass range ($10^6$-$10^9\,M_\odot$) remains relatively less constrained. In this mass regime, the corresponding Einstein radii on the milliarcsecond scale make Very Long Baseline Interferometry (VLBI) the most direct observational probe via milli-lensing of compact radio sources. In this paper, we present predictions for the abundance of PBH dark matter ($f_{\rm PBH}$) using the large SMILE sample of $\sim 5000$ flat-spectrum compact radio sources. Under the optimistic observational conditions (with an angular resolution of $1.5\,\mathrm{mas}$, a maximum image separation of $100\,\mathrm{mas}$, and a maximum detectable flux ratio of $40$), assuming that no milli-lensing events are confirmed, we obtain the projected 95% upper limit of $f_{\rm PBH}\lesssim0.12%$ in the intermediate-to-high mass range, which would be approximately an order of magnitude tighter than previous VLBI milli-lensing limits. Broader lognormal mass functions yield correspondingly weaker projected limits. Generalising the optical depth to account for magnification bias and finite-core resolvability changes these projected limits by only about $5$%. Moreover, we show that the predicted limits are highly sensitive to a small number of confirmed events, i.e., even one confirmed milli-lensing event would relax the projected upper limit to $0.20$%, highlighting the critical importance of robust candidate confirmation in the SMILE sample. Finally, under the optimistic baryonic accretion scenario, the PBH mass growth changes the projected limits by $\lesssim 1$% within the VLBI-sensitive mass range, confirming the robustness of our results.
发表机构
- Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University（北京师范大学前沿天文与天体物理研究所）
- School of Physics and Astronomy, Beijing Normal University（北京师范大学物理与天文学院）
- National Centre for Nuclear Research（波兰国家核研究中心）
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