论文标题
丝状结构在形成两个致密核心L1544和L694-2中的作用
Role of Filamentary Structures in the Formation of Two Dense Cores, L1544 and L694-2
论文作者
论文摘要
我们提出了两个Prestellar核心L1544和L694-2的映射结果,该结果嵌入了C $^{18} $ O(3-2),$^{13} $ CO(3-2),$^{12} $^{12} $(3-2),HCO $^+$^+$(4-3),以及H $^$^$^$(HO望远镜检查丝状结构在云层中密集芯形成中的作用,并具有L1544的新距离估计($ 175 _ { - 3}^{+4} $ PC)和L694-2($ 203 _ { - 7}^{+6} $ PC)。从这些观察结果中,我们发现,两个Prestellar核心的非热速度分散及其周围云的速度比声速小或可比。这可能表明在形成时间内已经对细丝和岩心的湍流已经消散。我们还发现,速度的周期性振荡与柱密度分布之间的$λ/4 $移动,这意味着可能存在沿细丝轴的引力核心形成流动运动。据估计,由于这些流动动力的质量积聚率为2-3 m $ _ \ odot $ myr $^{ - 1} $,与Serpens云相当,但比集线器丝,群集或高质量形成丝的质量要小得多。从这项研究中,我们建议我们的目标中的细丝可能是由碰撞云的冲击压缩形成的,然后岩心是通过细丝的重力碎片形成的,以演变为Prestellar阶段。我们得出的结论是,云中的丝状结构在整个密集核的整个过程中起着重要作用。
We present mapping results of two prestellar cores, L1544 and L694-2, embedded in filamentary clouds in C$^{18}$O (3-2), $^{13}$CO (3-2), $^{12}$CO (3-2), HCO$^+$ (4-3), and H$^{13}$CO$^+$ (4-3) with the JCMT telescope to examine the role of the filamentary structures in the formation of dense cores in the clouds, with new distance estimates for L1544 ($175_{-3}^{+4}$ pc) and L694-2 ($203_{-7}^{+6}$ pc). From these observations, we found that the non-thermal velocity dispersion of two prestellar cores and their surrounding clouds are smaller than or comparable to the sound speed. This may indicate that the turbulence has already been dissipated for both filaments and cores during their formation time. We also found a $λ/4$ shift between the periodic oscillations in the velocity and the column density distributions implying the possible presence of gravitational core-forming flow motion along the axis of the filament. The mass accretion rates due to these flow motions are estimated to be 2-3 M$_\odot$ Myr$^{-1}$, being comparable to that for Serpens cloud but much smaller than those for the Hub filaments, cluster, or high mass forming filaments by 1 or 2 order of magnitudes. From this study, we suggest that the filaments in our targets might be formed from the shock-compression of colliding clouds, and then the cores are formed by gravitational fragmentation of the filaments to evolve to the prestellar stage. We conclude that the filamentary structures in the clouds play an important role in the entire process of formation of dense cores and their evolution.