Ionized gas at the edge of the Central Molecular Zone
Ionized gas at the edge of the Central Molecular Zone
复制标题
中心分子区边缘的电离气体
DOI：
--
复制
发表时间：
2015
期刊：
影响因子：
--
通讯作者：
H. Wiesemeyer
中科院分区：
文献类型：
--
作者：
W. Langer;P. Goldsmith;J. Pineda;T. Velusamy;M. Requena;H. Wiesemeyer
为了确定位于SGR E附近CMZ边缘的电离气体的性质，我们使用SOFIA上的GREAT仪器在六个位置用光谱分辨的[C II]158微米和[N II]205微米的精细结构线观测了位于SGR E附近的CMZ边缘的一小部分，并使用Herschel HiFi动态条形图观测了[C II]。我们使用[N II]光谱和辐射传输模型来计算气体的电子密度，并使用[C II]图来照亮电离气体的形态和模拟CO暗H2的列密度。我们观测到了两个速度分量[C II]和[N II]，一个沿着视线到达与SGR E相关的-207公里/S的CO分子云，另一个在另一个CO云边缘外的-174公里/S处。从[N II]发射我们发现，对于这些特征，平均电子密度在大约5到25 cm-3的范围内。这种电子密度比磁盘中的热电离介质高得多。在-207 km/S云中CO暗H$2$层的柱密度约为1-2×10{21}cm-2，与理论模型相符。在电离气体中，CMZ在银河系半径内的延伸范围比在CO追踪的分子气体中延伸7到14pC。CMZ的边缘可能包含围绕中性分子材料的致密的热电离气体。N+的高分数丰度和高电子密度需要一个强的极紫外场，其光子通量为1e6到1e7光子cm-2}S{-1}，和/或在1e4K的温度和/或大的X射线通量下与氮进行有效的质子电荷交换。SGRE是一个大质量恒星形成区域，它是EUV辐射的潜在来源，可以使气体电离。此外，CMZ中的X射线源和漫反射X射线发射也是电离氮的候选对象。
To determine the properties of the ionized gas at the edge of the CMZ near Sgr E we observed a small portion of the edge of the CMZ near Sgr E with spectrally resolved [C II] 158 micron and [N II] 205 micron fine structure lines at six positions with the GREAT instrument on SOFIA and in [C II] using Herschel HIFI on-the-fly strip maps. We use the [N II] spectra along with a radiative transfer model to calculate the electron density of the gas and the [C II] maps to illuminate the morphology of the ionized gas and model the column density of CO-dark H2. We detect two [C II] and [N II] velocity components, one along the line of sight to a CO molecular cloud at -207 km/s associated with Sgr E and the other at -174 km/s outside the edge of another CO cloud. From the [N II] emission we find that the average electron density is in the range of about 5 to 25 cm{-3} for these features. This electron density is much higher than that of the warm ionized medium in the disk. The column density of the CO-dark H$_2$ layer in the -207 km/s cloud is about 1-2X10{21} cm{-2} in agreement with theoretical models. The CMZ extends further out in Galactic radius by 7 to 14 pc in ionized gas than it does in molecular gas traced by CO. The edge of the CMZ likely contains dense hot ionized gas surrounding the neutral molecular material. The high fractional abundance of N+ and high electron density require an intense EUV field with a photon flux of order 1e6 to 1e7 photons cm{-2} s{-1}, and/or efficient proton charge exchange with nitrogen, at temperatures of order 1e4 K, and/or a large flux of X-rays. Sgr E is a region of massive star formation which are a potential sources of the EUV radiation that can ionize the gas. In addition X-ray sources and the diffuse X-ray emission in the CMZ are candidates for ionizing nitrogen.
银河核心的红外 H 和 CO 研究：GCIRS 3 和 GCIRS 1W
DOI：
10.1088/0004-637x/786/2/96
发表时间：
2014
期刊：
The Astrophysical Journal
影响因子：
--
作者：
Geballe;Indriolo;Yusef-Zadeh;Henning
通讯作者：
Henning
GREAT/SOFIA 大气校准
影响因子：
6.5
作者：
Stutzki;Güsten;Requena- Torres;Wiesemeyer
通讯作者：
Wiesemeyer