用Gaia EDR3研究BRC 18的火箭效应
Investigation of Rocket Effect in BRC 18 using Gaia EDR3
摘要：
边缘云（BRC）是研究辐射驱动的恒星形成内爆模式的理想候选者，因为它们是触发恒星形成的潜在场所，位于H{ \sc ii}区域的边缘，显示出正在进行的恒星形成过程的证据。BRC 18位于由$λ$ Ori激发的相对较近（$\sim$ 400 pc）H{ \sc ii}区域的东部边缘。我们做了R波段偏振观测的17个候选年轻恒星对象（YSO）位于朝向BRC 18调查任何首选的磁盘相对于环境磁场和方向的高能光子从$λ$奥利。我们发现，磁盘是随机定向相对于投影磁场。使用距离和自行从\textit{Gaia} EDR 3的候选YSO，我们调查了可能的加速度的BRC 18，远离$λ$猎户座由于众所周知的“火箭效应”，通过假设候选YSO和BRC 18是运动学耦合。候选YSO的相对自行被发现显示出远离$λ$ Ori的趋势。我们计算了电离前沿方向的角度与候选YSO的相对自行之间的偏移，发现它接近于彼此平行。此外，我们发现了12个与已知候选YSO共同向BRC 18移动的源。这些共同流动的来源最有可能是年轻的，在以前为确定该区域潜在的青年组织而进行的调查中没有发现。
英文摘要：
Bright-rimmed clouds (BRCs) are ideal candidates to study radiation-driven implosion mode of star formation as they are potential sites of triggered star formation, located at the edges of H{\sc ii} regions, showing evidence of ongoing star formation processes. BRC 18 is located towards the eastern edge of relatively closer ($\sim$400 pc) H{\sc ii} region excited by $λ$ Ori. We made R-band polarimetric observations of 17 candidate young stellar objects (YSOs) located towards BRC 18 to investigate any preferred orientation of the discs with respect to the ambient magnetic field and the direction of energetic photons from $λ$ Ori. We found that the discs are oriented randomly with respect to the projected magnetic field. Using distances and proper motions from the \textit{Gaia} EDR3 of the candidate YSOs, we investigated the possible acceleration of BRC 18, away from $λ$ Ori due to the well known "Rocket Effect", by assuming that both the candidate YSOs and BRC 18 are kinematically coupled. The relative proper motions of the candidate YSOs are found to show a trend of moving away from $λ$ Ori. We computed the offset between the angle of the direction of the ionization front and the relative proper motion of the candidate YSOs and found it to lie close to being parallel to each other. Additionally, we found 12 sources that are comoving with the known candidate YSOs towards BRC 18. These comoving sources are most likely to be young and are missed in previous surveys conducted to identify potential YSOs of the region.
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