Feedback from Active Galactic Nuclei (AGN) and subsequent jet cocoons and outflow bubbles can have a significant impact on star formation in the host galaxy. To investigate feedback physics on small scales, we perform hydrodynamic simulations of realistically fast AGN winds striking Bonnor-Ebert (BE) spheres and examine gravitational collapse and ablation. We test AGN wind velocities ranging from 300--3,000 km s$^{-1}$ and wind densities ranging from 0.5--10 $m_\mathrm{p}\,\mathrm{cm}^{-3}$. We include heating and cooling of low- and high-temperature gas, self-gravity, and spatially correlated perturbations in the shock, with a maximum resolution of 0.01 pc. We find that the ram pressure is the most important factor that determines the fate of the cloud. High ram pressure winds increase fragmentation and decrease the star formation rate, but also cause star formation to occur on a much shorter time scale and with increased velocities of the newly formed stars. We find a threshold ram pressure of $\sim 2\times10^{-8}$ dyne cm$^{-2}$ above which stars are not formed because the resulting clumps have internal velocities large enough to prevent collapse. Our results indicate that simultaneous positive and negative feedback will be possible in a single galaxy as AGN wind parameters will vary with location within a galaxy.
Bonnor-Ebert sphere collapse in filamentary structures
Ludwig-Maximilians-Universität München（慕尼黑路德维希-马克西米利安大学）；Excellence Cluster ORIGINS（ORIGINS卓越集群）；Max-Planck Institute for Extraterrestrial Physics（马克斯·普朗克地外物理研究所）
On filament fragmentation and the impact of ambient environment on it
灯丝是恒星形成过程中至关重要的中介。最近的观察表明，- \textbf{(i)}他们中的一些是非奇异的实体，而是一束速度相干纤维，和\textbf{(ii)}，而大多数的长丝产卵核心窄于他们的出生丝，一些核心更广泛。我们探索这些问题，通过开发流体动力学模拟的一个最初的亚临界个别灯丝，允许从其附近的气体吸积和自引力下的演变。这里得到的结果支持的想法，纤维自然形成的长丝形成过程中。我们进一步认为，周围环境，即，外部压力的大小，而不是单独的细丝线质量，影响其演变的形态。我们观察到，无论外部压力如何，细丝都容易受到\emph{sausage}型不稳定性的影响。然而，这些碎片被挤压在一个压力与太阳附近相当的细丝中（$\sim 10^{4}$ K cm $^{-3}$）。相比之下，碎片是宽的和球形的--具有类似于稳定的Bonnor-Ebert球体的密度分布--当细丝经受更高的压力时，通常为$\ge 10^{5}$ K cm $^{-3}$，但为$\le 10^{6}$ K cm $^{-3}$）.在甚至更高的外部压力（$\ge 10^{7}$ K cm $^{-3}$）下，长丝倾向于断裂。这些观测结果共同表明，随着外部压力的增加，恒星形成的效率降低。
