发表机构
Harvard-Smithsonian Center for Astrophysics（哈佛-史密松天体物理中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究提出了一种由恒星潮汐撕裂驱动的自维持黑洞引擎机制，解释了潮汐撕裂事件发生率偏高及延迟时间分布晚期峰值的成因，相关事件多在红外波段显现
AI 中文摘要
潮汐撕裂事件（TDE）强烈倾向于发生在正在经历或正从恒星形成爆发中恢复的宿主星系，这意味着少数稀有类型的星系会产生大多数此类事件。每星系所需的发生率高达10⁻² gal⁻¹ yr⁻¹，仅靠恒星弛豫很难达到。核星团周围的分子云有助于设定弛豫率，为提高发生率提供了一条途径。我们表明，（后）星暴星系（其附近原型包含大型分子气体库）可能处于自维持循环中：增强的撕裂率通过未束缚碎片注入的动量压缩周围的云，更致密的云压缩星团，而星团会更快地撕裂恒星。只有当恒星开始碰撞时，这种失控才会停止。求解稳态时，发生率饱和为1.4×10⁻²(M_h/10⁶M_⊙)⁻⁰.⁸⁴ yr⁻¹，比10⁶M_⊙时的标准率高两个数量级，且由于恒星碰撞率，归一化还存在另外两个数量级的不确定性。三个独立要求——潮汐碎片超过活动星系核（AGN）反馈、分子云容纳在承载它们的盘内、以及尖峰的密度不超过观测到的核的密度——将恒星尖峰的扁平化限制为0.18≲f_*≲0.25。由于没有引擎能在低于黑洞质量阈值的情况下运行，在此之下形成的种子黑洞会保持黑暗，直到吸积使其跨越阈值，约1 Gyr后开启，为近期测量到的TDE延迟时间分布中的晚期峰值提供了自然解释。无论几何形状如何，核都被A_V≃50掩埋，因此大多数此类撕裂事件应在光学巡天中隐藏，而在红外波段显现。
英文摘要
Tidal disruption events (TDEs) strongly prefer host galaxies undergoing, or recovering from, a burst of star formation, implying that a rare minority of galaxy types produces most events. The required per-galaxy rates, as high as $10^{-2}$ gal$^{-1}$ yr$^{-1}$, are hard to achieve through stellar relaxation alone. Molecular clouds surrounding nuclear clusters help set the relaxation rate, offering a path to higher rates. We show that (post-)starburst galaxies, whose nearby prototypes contain large molecular gas reservoirs, are likely in a self-sustaining cycle: an enhanced disruption rate compresses the surrounding clouds through momentum injected by the unbound debris, the denser clouds compress the cluster, and the cluster disrupts stars faster still. The runaway is arrested only when stars begin to collide. Solving for the steady state, the rate saturates at $1.4\times10^{-2}(M_{\rm h}/10^{6}M_\odot)^{-0.84}$ yr$^{-1}$, two orders of magnitude above the canonical rate at $10^{6}M_\odot$, with a normalization uncertain by a further two orders of magnitude through the stellar collision rate. Three independent requirements --- that tidal debris outweigh AGN feedback, that the molecular clouds fit within the disk that holds them, and that the cusp be no denser than observed nuclei --- bound the flattening of the stellar cusp to $0.18 \lesssim f_\ast \lesssim 0.25$. Because no engine can run below a threshold black hole mass, holes seeded beneath it stay dark until accretion carries them across, switching on after $\sim 1$ Gyr and offering a natural explanation for the late peak recently measured in the TDE delay time distribution. The nucleus is buried under $A_V \simeq 50$ whatever its geometry, so most such disruptions should be hidden from optical surveys and emerge instead in the infrared.
Comments28 pages, 4 figures. Submitted to the Open Journal of Astrophysics
