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ISO1 LONG WAVELENGTH SPECTROGRAPH OBSERVATIONS OF COLD DUST IN GALAXIES

机译:ISO1星系中冷尘的长波谱图观察

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We describe observations of five nearby galaxies obtained using the Long Wavelength Spectrograph (LWS) on the Infrared Space Observatory (ISO). We observed five galaxies, using spectrograph apertures positioned at the galactic center and in the outskirts of the disk, to compare the spectral energy distribu- tion of the emitting dust at different positions. The central spectra are typical of those inferred previously from IRAS data; peaking at about 100 μm with estimated dust temperatures of Td = 30--35 K. However, there is a rapid change in the spectral energy distribution with increasing galactocentric distance. In the outer regions the spectra are flat, or still rising, out to 197 μm, indicating a predominantly cold dust component with Td < 20 K. In the central regions, the inferred cold dust component is 2--10 times more massive than the warm dust, and it increasingly dominates the mass and spectral energy distribution in the outer regions. We discuss reasons for believing that emission beyond ≈l50 μm in disk galaxies is associated with a separate component of dust with an extended distribution that may be associated with a possible molecular halo.
机译:我们描述了在红外空间天文台(ISO)上使用长波光谱仪(LWS)获得的五个附近星系的观测结果。我们使用位于银河系中心和磁盘郊区的光谱仪孔径观察了五个星系,以比较不同位置发射尘埃的光谱能量分布。中心光谱是以前从IRAS数据推论得出的典型光谱。尘埃温度估计为Td = 30--35 K时,其峰值在约100μm处。然而,光谱能量分布会随着半中心距的增加而迅速变化。在外围区域,光谱平坦或仍上升到197μm,表明主要是Td <20 K的冷尘成分。在中心区域,推断出的冷尘成分的质量是Td <20 K的2--10倍。温暖的尘埃,它逐渐占据了外部区域的质量和光谱能量分布的主导地位。我们讨论了以下理由:人们认为,盘状星系中超过≈150μm的发射与尘埃的单独成分有关,而尘埃的扩展分布可能与可能的分子光晕有关。

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