恒星形成区“绿模糊”发射源的直接光谱鉴别
Direct Spectroscopic Identification of the Origin of 'Green Fuzzy' Emission in Star Forming Regions
摘要：
“绿色模糊”或“扩展的绿色物体”是在最近的斯皮策GLIMPSE调查数据中发现的。这些扩展源在4.5um IRAC通道图像中具有增强的发射（当从斯皮策数据制作3色RGB图像时，其通常被分配为绿色）。绿色模糊经常在大质量年轻恒星附近发现，并且已经确定它们在某些情况下与外流有关。然而，这种增强发射的光谱载体仍然不确定。虽然有人认为Br Alpha、H2、[Fe II]和/或广泛的CO排放可能有助于增强这些天体的4.5微米通量，但迄今为止还没有直接观测到这些天体的4- 5微米光谱。我们在这里报告的第一个直接光谱鉴定的绿色模糊发射的起源。我们获得了空间分辨的L和M波段光谱的两个绿色模糊源使用NIRI的双子座北望远镜。在一个源的情况下，G19.88-0.53，我们检测到三个单独的节点的绿色模糊发射周围的源。结的发射光谱为纯氢分子谱线，在4- 5 μ m波长范围内主要发射4.695 μ m v=0-0 S（9）谱线，没有检测到连续谱成分。我们对G19.88-0.53的实验数据证明，绿色模糊发射主要是由于IRAC 4.5 μ m通道带通内的分子氢发射线。然而，观测到的另一个目标G49.27-0.34没有表现出任何线发射，似乎是一个嵌入的大质量年轻恒星物体，具有彗星状的UC HII区域。我们认为，在3- 8 um波长范围内的消光效应和IRAC RGB图像中4.5um滤光片的颜色拉伸的夸大可能导致嵌入源，如这一个错误地出现“绿色”。
英文摘要：
"Green fuzzies" or "extended green objects" were discovered in the recent Spitzer GLIMPSE survey data. These extended sources have enhanced emission in the 4.5um IRAC channel images (which are generally assigned to be green when making 3-color RGB images from Spitzer data). Green fuzzies are frequently found in the vicinities of massive young stellar objects, and it has been established that they are in some cases associated with outflows. Nevertheless, the spectral carrier(s) of this enhanced emission is still uncertain. Although it has been suggested that Br Alpha, H2, [Fe II], and/or broad CO emission may be contributing to and enhancing the 4.5um flux from these objects, to date there have been no direct observations of the 4-5um spectra of these objects. We report here on the first direct spectroscopic identification of the origin of the green fuzzy emission. We obtained spatially resolved L and M band spectra for two green fuzzy sources using NIRI on the Gemini North telescope. In the case of one source, G19.88-0.53, we detect three individual knots of green fuzzy emission around the source. The knots exhibit a pure molecular hydrogen line emission spectrum, with the 4.695um v=0-0 S(9) line dominating the emission in the 4-5um wavelength range, and no detected continuum component. Our data for G19.88-0.53 prove that green fuzzy emission can be due primarily to emission lines of molecular hydrogen within the bandpass of the IRAC 4.5um channel. However, the other target observed, G49.27-0.34, does not exhibit any line emission and appears to be an embedded massive young stellar object with a cometary UC HII region. We suggest that the effects of extinction in the 3-8um wavelength range and an exaggeration in the color stretch of the 4.5um filter in IRAC RGB images could lead to embedded sources such as this one falsely appearing "green".
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