Studies of Warm and Diffuse Gas and High Ionization Rate Near the Galactic Center Using Infrared Spectra of H3+ and CO

奥卡博士和他的团队通过测量（H3）+和CO对中央分子区的红外吸收来研究银河系中心温暖弥漫气体的性质。质子化的分子氢（H3）+，是包含该分子离子的大区域的密度、温度、电离率和体积填充因子的示踪剂。它也是其他在弥漫星际介质中难以测量的多原子分子的示踪剂。（H3）+的发现和沿沿着14条视线的观测表明，温暖的扩散气体（T约为250 K，密度为每立方厘米100-1000个粒子）表明存在温暖的扩散成分，以更长的已知成分的致密分子，热电离和超热等离子体。研究人员发现，这种气体的体积填充因子似乎非常高，并且银河系中心附近这些视线的温暖扩散气体的电离率比这些地区的预期值高出一个数量级。目前的工作调查更多的视线对银河系中心使用新的背景恒星，从斯皮策GLIMPSE（银河遗产红外线中面调查非凡）数据库和CO观测。的数据进行比较与新的赫歇尔观测（H2O）+和无线电和红外光谱的CO充分表征的物理性质的温暖的扩散气体和其他成分在复杂的和动态的地区在银河系中心。该项目培养一名观测红外天文学和分子天体物理学博士后研究员。

Dr. Oka and his team study the properties of warm, diffuse gas in the Galactic center by measuring (H3)+ and CO infrared absorption towards the Central Molecular Zone. Protonated molecular hydrogen, (H3)+, is a tracer of the density, temperature, ionization rate, and volume filling factor of the large regions containing this molecular ion. It is also a tracer for other polyatomic molecules that are difficult to measure in the diffuse interstellar medium. The (H3)+ discovery and observations along 14 sight lines showed that warm diffuse gas (T about 250 K, density of 100-1000 particles per cubic centimeter) indicates the presence of a warm, diffuse component to the longer known components of dense-molecular, hot-ionized, and ultra-hot plasma. The researchers found that the volume filling factor of this gas appears to be very high, and the ionization rate for the warm diffuse gas an order of magnitude higher values for these sight lines near the Galactic Center than expected for these regions. The present work investigates more sight lines towards the Galactic center using new background stars that are selected from the Spitzer GLIMPSE (Galactic Legacy Infrared Mid-Plane Survey Extraordinaire) database and CO observations. The data are compared with new Herschel observations of (H2O)+ and radio and infrared spectra of CO to fully characterize the physical properties of the warm diffuse gas and the other components in the complex and dynamical regions at the Galactic center. This project trains a post-doctoral fellow in observational infrared astronomy and molecular astrophysics.