Dense Molecular Clumps with Large Blue Asymmetries: Evidence for Collapse
Green Bank Observatory（格林班克天文台）；USRA SOFIA Science Center, NASA Ames Research Center（美国研究联盟 SOFIA 科学中心，NASA 艾姆斯研究中心）；School of Mathematical and Physical Sciences, University of Newcastle（纽卡斯尔大学数学与物理科学学院）；Physics Department, Boston University（波士顿大学物理系）；Space Science Institute（太空科学研究所）；I. Physikalisches Institut, Universität zu Köln（科隆大学第一物理研究所）；Instituto de Astronomía, Universidad Católica del Norte（北天主教大学天文学研究所）；Research School of Astronomy and Astrophysics, Australian National University（澳大利亚国立大学天文与天体物理研究学院）
James M. Jackson, J. Scott Whitaker, Edward Chambers, Robert Simon, Cristian Guevara, David Allingham, Philippa Patterson, Nicholas Killerby-Smith, Jacob Askew,… 展开作者
James M. Jackson, J. Scott Whitaker, Edward Chambers, Robert Simon, Cristian Guevara, David Allingham, Philippa Patterson, Nicholas Killerby-Smith, Jacob Askew, Patricio Sanhueza, Ian W. Stephens, Anika Shmiedeke, Jacob Askew, Robert Loughnane
An analysis of the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey has produced a sample of 27 candidate dense molecular clumps with large collapse motions, as revealed by large ``blue'' asymmetrical line profiles of the optically thick \hcop\, line. %with respect to the optically thin \nthp\, line. New, more sensitive molecular line observations of this sample, conducted with the Mopra 22-m telescope, confirm the blue asymmetries in the \hcop\, line profiles, with large, positive values of the asymmetry parameter $A$ ($\bar{A}_{HCO^+} = 0.69\pm0.01$), and positive, but smaller asymmetries in the \hcn\, and \hnc\, lines: ($\bar{A}_{HCN} = 0.35\pm0.01$ and $\bar{A}_{HNC} = 0.28\pm0.01$), as expected for a less optically thick tracer in collapsing clumps. The small, positive mean asymmetry parameters for \cch\, and \htcop, $\bar{A}_{C_2H} = 0.15\pm0.02$ and $\bar{A}_{H^{13}CO^+} = 0.18\pm0.03$, likely indicate slightly optically thick emission for at least some clumps. The hyperfine ratios for \nthp\, are in their optically thin, LTE, values, but for \hcn\ they are not; the $F=1 \to 1$ hyperfine line shows abnormally weak intensities. A simple two-component model shows that self-absorption of the background $F = 1 \to 1$ hyperfine line by the main $F = 2 \to 1$ hyperfine line of a cold, foreground, redshifted cloud can reproduce the observed \hcn\, hyperfine intensities and match the \hcn\, and \hcop\, line profiles. All of these results are consistent with self-absorption of the optically thick lines on the red side of the profile, as expected for collapsing clumps. A simple two-cloud model suggests that this sample represents dense clumps with extreme collapse velocities, $V_{inf} \sim 2.4$ \kms.
Global and Local Infall in the ASHES Sample (GLASHES). II. Asymmetric Line Profiles around Dense Cores in 70 $μ$m Dark Massive Clumps
The University of Tokyo（东京大学）；Green Bank Observatory（格林班克天文台）；USRA SOFIA Science Center, NASA Ames Research Center（美国研究联合体SOFIA科学中心，NASA艾姆斯研究中心）；University of Newcastle（纽卡斯尔大学）
Comprehensive JWST+ALMA Study on the Extended Ly$α$ Emitters, Himiko and CR7 at $z\sim 7$: Blue Major Merger Systems in Stark Contrast to Submillimeter Galaxies
The Graduate University for Advanced Studies, SOKENDAI（高级研究大学院大学）；National Astronomical Observatory of Japan（日本国立天文台）；Institute for Cosmic Ray Research, The University of Tokyo（东京大学宇宙射线研究所）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo（东京大学 Kavli 宇宙物理数学研究所）；Department of Astronomy, Graduate School of Science, the University of Tokyo（东京大学理学研究科天文学专攻）；Department of Physics, The University of Tokyo（东京大学物理学系）；Center for Computational Astrophysics, Flatiron Institute（西蒙斯基金会平顿研究所计算天体物理中心）；Center for Computational Sciences, University of Tsukuba（筑波大学计算科学中心）；University of Toronto（多伦多大学）；Dunlap Institute for Astronomy and Astrophysics（邓普勒天文与天体物理研究所）；Kanazawa University（金泽大学）；Department of General Systems Studies, Graduate School of Arts and Sciences, The University of Tokyo（东京大学大学院综合文化研究科一般系统研究专攻）；Institute of Astronomy, Graduate School of Science, The University of Tokyo（东京大学理学研究科天文学专攻天文学研究所）；Research Center for the Early Universe, Graduate School of Science, The University of Tokyo（东京大学理学研究科宇宙早期现象研究中心）
The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles (ASSEMBLE): Core Growth, Cluster Contraction, and Primordial Mass Segregation
Planck Galactic Cold Clumps in Two Regions: the First Quadrant and the Anti-Center Direction Region
用PMO 13.7米望远镜在$^{12}$ CO、$^{13}$ CO和C $^{18}$ O J=1-0谱线上观测到了65个来自第一象限（IQuad）的普朗克银河冷团（PGCC）和39个来自反中心方向区（ACent）的普朗克银河冷团（PGCC）。除了12个IQuad和8个ACent PGCC未检测到C $^{18}$ O外，所有三条线均检测到所有靶标。在IQuad和ACent中分别获得了76个和49个速度分量。从76个IQuad团块中提取了146个核心，从49个ACent团块中提取了100个核心。IQuad内核和ACent内核的平均T $_{\mathrm{ex}}$分别为12.4 K和12.1 K。IQuad核和ACent核的$^{13}$ CO的平均线宽分别为1.55 km s $^{-1}$和1.77 km s $^{-1}$。在检测到的核心中，IQuad中的24个和ACent中的13个具有不对称的线轮廓。IQuad和ACent中的小蓝色过量值分别为$\sim$ 0.03和0.01，表明这些PGCC核心中的恒星形成并不活跃。核质量函数对高质量端的幂律拟合给出IQuad中的-0.57和ACent中的-1.02的指数，其比\citeauthor{1955ApJ...121..161S}给出的初始质量函数的斜率更平坦。IQuad核心的大周转质量值为28 M $_{\odot}$，…
Line Profiles of Cores within Clusters. III. What is the most reliable tracer of core collapse in dense clusters?
最近的观测和理论研究强调了分子云内的网状结构作为恒星形成场所的重要性。由于这样的环境比孤立的核心更复杂，因此有必要了解从具有非球形几何形状的坍缩核心观察到的线轮廓如何受到细丝的影响。在这项研究中，我们调查线轮廓的不对称性进行辐射转移计算的流体动力学模型的三个崩溃的核心，嵌入在细丝。我们将结果与孤立核心的预期结果进行比较。我们使用常数丰度定律模拟了光学厚（HCN，HCO $^+$）和光学薄（N $_2$ H $^+$，H $^{13}$ CO $^+$）分子的五个最低转动跃迁线（J = 1-0，2-1，3-2，4-3和5-4）。我们发现，不到50%的模拟（1-0）过渡线显示蓝色的下落不对称，由于周围的灯丝遮蔽。然而，当在（4-3）转变中观察时，具有蓝色不对称发射线轮廓的塌陷芯的分数上升到90%。由于朝向坍缩核心的致密气体可以激发更高的转动态，因此上能级跃迁更有可能产生蓝色的不对称发射轮廓。我们的结论是，即使在不规则的，嵌入式核心可以跟踪下落气体运动与蓝色不对称线轮廓的光学粗线观察更高的过渡。HCN的（4-3）跃迁是塌缩运动的最佳示踪剂，但HCN和HCO的（3-2）和（5-4）跃迁$^+$也是很好的示踪剂。
