发表机构
Guangzhou University; Key Laboratory for Astronomical Observation and Technology of Guangzhou; Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province; Universitat Politècnica de València; Max-Planck-Institute for Extraterrestrial Physics; Kavli Institute for Astronomy and Astrophysics（广州大学; 广州市天文观测与技术重点实验室; 广东省教育厅天文学科学与技术研究实验室; 瓦伦西亚理工大学; 马克斯·普朗克地外物理研究所; 卡弗里天体物理学研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用GNC蒙特卡洛代码模拟核星团，发现恒星碰撞会平坦化密度尖峰，且与黑洞增长协同作用，使大质量星系成为观测破坏性恒星碰撞瞬变事件的主要目标。
AI 中文摘要
星系中心拥有最致密的恒星环境，其中大质量黑洞（MBH）将恒星加速到如此高的速度，以至于直接碰撞可能导致高能现象，例如引力波源、千新星和类似超新星的瞬变事件。这些碰撞可以重塑星团的密度轮廓，并释放气体，这些气体随后可能被MBH吸积。然而，在质量增长的MBH周围，由自洽动力学驱动的此类现象的演化速率在很大程度上仍未得到探索。在本工作中，我们利用GNC蒙特卡洛代码模拟了不同质量和密度轮廓的核星团（NSCs），该代码自洽地模拟了恒星动力学以及释放气体的后续吸积。我们发现，恒星碰撞在约0.1-1 Gyr内使最内层区域（$r \lesssim 10^{-3}-10^{-2}$ pc）的密度尖峰变得平坦。虽然陡峭尖峰中的高初始碰撞率因恒星消耗而迅速下降，但碰撞与MBH增长之间的相互作用仅在质量较大的NSCs（$M_\star \sim 10^9 M_\odot$）中才重要。随着MBH的增长，恒星速度的增加使平衡转向破坏性碰撞，其相对速度可达$\gtrsim 2500 {\rm \\,km\\,s^{-1}}$。因此，在质量较大的星团中，当今的破坏性碰撞率仍然很高（$10^{-4}\sim 10^{-3}{\rm yr}^{-1}$），而在类似银河系的NSCs中则较小，在较小的NSCs中则可忽略不计。我们的结果凸显了恒星动力学与MBH增长之间的关键协同作用，将大质量星系确定为观测破坏性恒星碰撞瞬变事件的主要目标。
英文摘要
The centers of galaxies harbor the densest stellar environments, where a massive black hole (MBH) accelerates stars to such high velocities that direct collisions can result in high-energetic phenomena, such as gravitational wave sources, kilonovae, and supernova-like transients. These collisions can reshape the cluster's density profile and release gas that can be subsequently accreted by the MBH. However, the evolving rates of such phenomena from self-consistent dynamics around mass-growing MBHs remain largely unexplored. In this work, we simulate nuclear star clusters (NSCs) across a range of masses and density profiles by employing the GNC Monte Carlo code, that self-consistently models stellar dynamics and the subsequent accretion of released gas. We find that stellar collisions flatten the density cusp in the innermost regions ($r \lesssim 10^{-3}-10^{-2}$ pc) within $\sim 0.1-1$ Gyr. While high initial collision rates in steep cusps quickly decline due to stellar depletion, the interplay between collisions and MBH growth is important only in massive NSCs ($M_\star \sim 10^9 M_\odot$). As MBH grows, increased stellar velocities shift the balance toward destructive collisions of which relative velocities can be $\gtrsim 2500 {\rm \,km\,s^{-1}}$. Consequently, present-day destructive collision rates in massive clusters remain high ($10^{-4}\sim 10^{-3}{\rm yr}^{-1}$), whereas they are smaller in Milky Way-like NSCs or negligible in smaller NSCs. Our results highlight a crucial synergy between stellar dynamics and MBH growth, identifying massive galaxies as prime targets for observing transients from destructive stellar collisions.
Comments18 pages, 10 figures, accepted for publication in ApJ
