We present a new large-scale (4 square degrees) simultaneous $^{12}$CO, $^{13}$CO, and C$^{18}$O ($J$=1$-$0) mapping of L1188 with the PMO 13.7-m telescope. Our observations have revealed that L1188 consists of two nearly orthogonal filamentary molecular clouds at two clearly separated velocities. Toward the intersection showing large velocity spreads, we find several bridging features connecting the two clouds in velocity, and an open arc structure which exhibits high excitation temperatures, enhanced $^{12}$CO and $^{13}$CO emission, and broad $^{12}$CO line wings. This agrees with the scenario that the two clouds are colliding with each other. The distribution of young stellar object (YSO) candidates implies an enhancement of star formation in the intersection of the two clouds. We suggest that a cloud-cloud collision happened in L1188 about 1~Myr ago, possibly triggering the formation of low- and intermediate-mass YSOs in the intersection.
Triggering Collapse of the Presolar Dense Cloud Core and Injecting Short-Lived Radioisotopes with a Shock Wave. III. Rotating Three Dimensional Cloud Cores
Triggering Collapse of the Presolar Dense Cloud Core and Injecting Short-Lived Radioisotopes with a Shock Wave. VI. Protostar and Protoplanetary Disk Formation
自1976年以来,对短寿命放射性同位素(SLRI)$^{26}$ Al的初始陨石丰度的宇宙化学评估一直相当稳定,而对SLRI $^{60}$ Fe的初始丰度的估计最近变化很大。在这个范围的高端,$^{60}$ Fe的初始丰度似乎需要在核心坍缩超新星中进行$^{60}$ Fe核合成,然后在$\sim$ 100万年内并入原始陨石成分。本文继续详细探讨这一经典的情况下,使用的模型的分子云的核心,已被合适的冲击波前锋,导致冲击波前锋气体注入到崩溃的云通过瑞利-泰勒手指形成的冲击波-云界面的自引力崩溃。如前所述,这些模型使用FLASH三维自适应网格细化(AMR)重力流体动力学代码进行计算。虽然以前的模型使用FLASH 2.5,但新模型使用FLASH 4.3,它允许引入下沉粒子来代表新形成的原恒星物体。下沉粒子允许模型在时间上向前推进到$\sim 1 M_\odot$原恒星形成的阶段,由旋转的原行星盘围绕。因此,这些模型能够定义什么类型的目标云核心是必要的超新星触发的情况下,产生一个合理的计划注入SLRI到太阳前云核心:$\sim 3 M_\odot$云核心旋转的速度为$\sim 3 \times 10^{-14}$ rad s $^{-1}$或更高。
Triggering Collapse of the Presolar Dense Cloud Core and Injecting Short-Lived Radioisotopes with a Shock Wave. II. Varied Shock Wave and Cloud Core Parameters
Ionisation-induced star formation III: Effects of external triggering on the IMF in clusters
我们报告的光滑粒子流体动力学(SPH)模拟的影响湍流$\sim2\times10^{3}$ M $_{\odot}$星-形成分子云的辐射由外部源的电离光子。我们发现电离辐射对气体形态有显著的影响,但对触发恒星的作用不太重要。恒星形成的速率和形态在很大程度上取决于湍流速度场产生的气体结构,反馈对恒星初始质量函数没有明显的影响。虽然许多年轻的恒星是在位于电离前沿附近的致密气体中发现的,但大多数这些物体也是在没有反馈的情况下形成的。电离在云的扩散区域有更强的作用,它会把低密度的气体扫走,否则这些气体就不会形成恒星,成为引力不稳定的团块。然而,即使在这些区域,恒星之间的动力学相互作用也会迅速消除它们的位置和速度与电离前沿之间的相关性。
The Minimum Mass of Rotating Main Sequence Stars and its Impact on the Nature of Extended Main Sequence Turnoffs in Intermediate-Age Star Clusters in the Magellanic Clouds
扩展主序星关闭(eMSTO)是麦哲伦星云中年轻和中等年龄星团色星等图(CMD)的一个共同特征。eMSTO的性质仍有争议。最受欢迎的场景是扩展的恒星形成和恒星旋转速率的范围。本文研究了大麦云星云(LMC)中年轻星团主序(MS)中扭结特征的含义。在对7亿年前的星系团NGC 1831进行的新的\emph{Hubble Space Telescope}观测中,这种扭折非常清楚地显示出来,并且位于CMD中多个或宽的MS合并成一个MS的区域之下,这些MS已知出现在年轻的星系团中,并且被认为是由于旋转速率的变化,扭折发生在初始恒星质量为$1.45 \pm 0.02\;M_{\odot}$的时候;我们认为,它代表了一个质量下限,低于这个下限,在这些星团的金属丰度下,自转对恒星能量输出的影响可以忽略不计。评估的位置,这样的初始质量的恒星在CMD的大规模LMC星团的年龄为$\sim\,$ 1.7 Gyr的功能广泛的eMSTO,我们发现,这样的恒星位于一个区域的eMSTO已经显着宽比MS下面it. This强烈建议恒星旋转\emph{cannot}充分解释了广泛的eMSTO在大规模的中期年龄集群的麦哲伦云。恒星年龄的分布似乎仍然需要解释eMSTO现象。
Three-Dimensional Distributions of Type II Cepheids and Anomalous Cepheids in the Magellanic Clouds. Do these Stars Belong to the Old, Young or Intermediate-Age Population?
Intermediate-Mass Stripped Stars in the Magellanic Clouds: Forward Modeling the Observed Population Discovered Via UV Excess
California Institute of Technology(加州理工学院);KU Leuven(荷语鲁汶大学);University of Toronto(多伦多大学);Institute of Science and Technology Austria (ISTA)(奥地利科学与技术研究所)
Population Parameters of Intermediate-Age Star Clusters in the Large Magellanic Cloud. II. New Insights from Extended Main Sequence Turnoffs in 7 Star Clusters
Population Parameters of Intermediate-Age Star Clusters in the Large Magellanic Cloud. III. Dynamical Evidence for a Range of Ages Being Responsible for Extended Main Sequence Turnoffs