Infrared Detection of Abundant CS in the Hot Core AFGL 2591 at High Spectral Resolution with SOFIA/EXES
Infrared Detection of Abundant CS in the Hot Core AFGL 2591 at High Spectral Resolution with SOFIA/EXES
复制标题
使用 SOFIA/EXES 以高光谱分辨率红外检测热核心 AFGL 2591 中丰富的 CS
DOI：
10.3847/2041-8213/aaeb23
复制
发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Alexander G. G. M. Tielens
中科院分区：
文献类型：
--
作者：
A. G. Barr;A. Boogert;C. DeWitt;E. Montiel;M. Richter;N. Indriolo;D. Neufeld;Y. Pendleton;J. Chiar;Ryan Dungee;Alexander G. G. M. Tielens
本文利用平流层红外天文观测台（SOFIA）上的梯队-交叉梯队光谱仪（EXES）对大质量原恒星AFGL 2591的热分子核进行了5-8 μm谱线测量。我们利用红外望远镜设施（IRTF）上的iSHELL仪器在4.5 μm左右的大气M波段进行了地面研究，并利用IRTF上的德克萨斯梯队交叉梯队光谱仪（TEXES）对8 ~ 13 μm的全n波段窗口进行了研究。在此，我们首次探测到该源中CS的旋转振动跃迁。CS的吸收谱线平均集中在- 10 km s−1附近，其谱线宽度与13CO的热组分（约10 km s−1）比较好。CS，热13CO和12CO v = 1-2的温度一致，约为700 K。我们得到了CO和H2的CS丰度分别为8 × 10−3和2 × 10−6。相对于周围云层（1 × 10−8），CS丰度的增强可能反映了H2S冰的升华，随后发生气相反应形成CS。跃迁处于局部热力学平衡，我们得出密度为>107 cm−3，对应于<0.04″的吸收区。EXES对CS的观测很可能深入到热核，到流出物的底部。亚毫米和红外观测通过系统速度、线宽、温度以及CS丰度的差异显示了热核的不同组成部分。
We have performed a 5–8 μm spectral line survey of the hot molecular core associated with the massive protostar AFGL 2591, using the Echelon-Cross-Echelle Spectrograph (EXES) on board the Stratospheric Observatory for Infrared Astronomy (SOFIA). We have supplemented these data with a ground-based study in the atmospheric M band around 4.5 μm using the iSHELL instrument on the Infrared Telescope Facility (IRTF), and the full N-band window from 8 to 13 μm using the Texas Echelon Cross Echelle Spectrograph (TEXES) on the IRTF. Here we present the first detection of rovibrational transitions of CS in this source. The absorption lines are centered on average around −10 km s−1 and the line widths of CS compare well with the hot component of 13CO (around 10 km s−1). Temperatures for CS, hot 13CO, and 12CO v = 1–2 agree well and are around 700 K. We derive a CS abundance of 8 × 10−3 and 2 × 10−6 with respect to CO and H2, respectively. This enhanced CS abundance with respect to the surrounding cloud (1 × 10−8) may reflect sublimation of H2S ice followed by gas-phase reactions to form CS. Transitions are in local thermodynamic equilibrium and we derive a density of >107 cm−3, which corresponds to an absorbing region of <0.04″. EXES observations of CS are likely to probe deeply into the hot core, to the base of the outflow. Submillimeter and infrared observations trace different components of the hot core as revealed by the difference in systemic velocities, line widths, and temperatures, as well as the CS abundance.