AFGL 2591周围振动激发的HCN：原恒星结构的探测
Vibrationally Excited HCN around AFGL 2591: A Probe of Protostellar Structure
摘要：
具有亚毫米级转动跃迁的振动激发分子是探测原恒星附近物理条件的潜在优秀探针。本研究使用HCN（4-3）的v=1和v=2振转模的观测来探测这种环境。这些振转谱线的存在与否和相对强度探测了与原恒星盘相关的温暖致密物质中的气体激发机制和物理条件。我们目前的试点观测从海因里希赫兹亚毫米望远镜（HHSMT）和后续观测从亚毫米阵列（SMA）。观察到所有振动激发HCN（4-3）v=0、v=1和v=2的谱线。三条v=2的谱线强度大致相等，这意味着碰撞激发的密度大于（10^10 cm^-3），发射气体的温度大于1000 K。这种温暖、高密度的物质应该可以直接追踪在原恒星的包层和盘环境中形成的结构。此外，v=2的发射线的形状可能表明开普勒圆盘。这封信演示了这种技术的实用性，这是特别感兴趣的，由于最近就职的阿塔卡马大型毫米波阵列（ALMA）。
英文摘要：
Vibrationally excited molecules with sub-mm rotational transitions are potentially excellent probes of physical conditions near protostars. This study uses observations of the v=1 and v=2 ro-vibrational modes of HCN (4-3) to probe this environment. The presence or absence and relative strengths of these ro-vibrational lines probe the gas excitation mechanism and physical conditions in warm, dense material associated with protostellar disks. We present pilot observations from the Heinrich Hertz Submillimeter Telescope (HHSMT) and followup observations from the Submillimeter Array (SMA). All vibrationally excited HCN (4-3) v=0, v=1, and v=2 lines were observed. The existence of the three v=2 lines at approximately equal intensity imply collisional excitation with a density of greater than (10^10 cm^-3) and a temperature of >1000 K for the emitting gas. This warm, high density material should directly trace structures formed in the protostellar envelope and disk environment. Further, the line shapes of the v=2 emission may suggest a Keplerian disk. This letter demonstrates the utility of this technique which is of particular interest due to the recent inauguration of the Atacama Large Millimeter Array (ALMA).
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