Detection of interstellar oxidaniumyl: Abundant H2O+ towards the star-forming regions DR21, Sgr B2, and NGC6334
Detection of interstellar oxidaniumyl: Abundant H2O+ towards the star-forming regions DR21, Sgr B2, and NGC6334
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DOI：
10.1051/0004-6361/201014577
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发表时间：
2010-07-01
影响因子：
6.5
通讯作者：
Zmuidzinas, J.
中科院分区：
文献类型：
--
作者：
Ossenkopf, V.;Mueller, H. S. P.;Zmuidzinas, J.
目标。我们确定了一个突出的吸收功能在1115 GHz，检测到的第一HIFI光谱对高质量的恒星形成区域，并解释其天体物理学的起源。H2O+基态旋转跃迁的特征超精细模式，以及在此频率范围内缺乏其他已知的低能量跃迁，将该特征识别为H2O+对尘埃连续背景的吸收，并使我们能够推导出吸收气体的速度分布。通过与DR 21恒星形成区其他示踪物的速度剖面比较，我们确定了该跃迁的频率和形成条件。在DR 21中，H2O+的速度分布与158 μ m处的[C II]线和OH cm波吸收相匹配，这两种速度分布都源于面向H II区域的热而致密的团块表面，并受到气泡流出的动态影响。漫射前景气体主导朝向Sgr B2的吸收。吸收线的积分强度使我们能够推导出NGC 6334中H2O+柱密度的下限为7.2 x 10（12）cm（-2），DR 21中为2.3 x 10（13）cm（-2），Sgr B2中为1.1 x 10（15）cm（-2）。
Aims. We identify a prominent absorption feature at 1115 GHz, detected in first HIFI spectra towards high-mass star-forming regions, and interpret its astrophysical origin.Methods. The characteristic hyperfine pattern of the H2O+ ground-state rotational transition, and the lack of other known low-energy transitions in this frequency range, identifies the feature as H2O+ absorption against the dust continuum background and allows us to derive the velocity profile of the absorbing gas. By comparing this velocity profile with velocity profiles of other tracers in the DR21 star-forming region, we constrain the frequency of the transition and the conditions for its formation.Results. In DR21, the velocity distribution of H2O+ matches that of the [C II] line at 158 mu m and of OH cm-wave absorption, both stemming from the hot and dense clump surfaces facing the H II-region and dynamically affected by the blister outflow. Diffuse foreground gas dominates the absorption towards Sgr B2. The integrated intensity of the absorption line allows us to derive lower limits to the H2O+ column density of 7.2 x 10(12) cm(-2) in NGC 6334, 2.3 x 10(13) cm(-2) in DR21, and 1.1 x 10(15) cm(-2) in Sgr B2.