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M101: Spectral Observations of H ii Regions and Their Physical Properties

机译:M101:H ii区的光谱观测及其物理性质

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By using the Hectospec 6.5 m Multiple Mirror Telescope and the 2.16 m telescope of the National Astronomical Observatories, of the Chinese Academy of Sciences, we obtained 188 high signal-to-noise ratio spectra of regions in the nearby galaxy M101, which is the largest spectroscopic sample of regions for this galaxy so far. These spectra cover a wide range of regions on M101, which enables us to analyze two-dimensional distributions of its physical properties. The physical parameters are derived from emission lines or stellar continua, including stellar population age, electron temperature, oxygen abundance, etc. The oxygen abundances are derived using two empirical methods based on O3N2 and R 23 indicators, as well as the direct method when is available. By applying the harmonic decomposition analysis to the velocity field, we obtained a line-of-sight rotation velocity of 71 and a position angle of 36°. The stellar age profile shows an old stellar population in the galaxy center and a relatively young stellar population in outer regions, suggesting an old bulge and a young disk. The oxygen abundance profile exhibits a clear break at ~18 kpc, with a gradient of ?0.0364 dex kpc?1 in the inner region and ?0.00686 dex kpc?1 in the outer region. Our results agree with the "inside-out" disk growth scenario of M101.
机译:通过使用中国科学院国家天文台的Hectospec 6.5 m多镜望远镜和2.16 m望远镜,我们获得了附近最大星系M101中区域的188个高信噪比光谱迄今为止,该星系区域的光谱样本。这些光谱覆盖了M101上的广泛区域,这使我们能够分析其物理特性的二维分布。物理参数来自发射谱线或恒星连续体,包括恒星种群年龄,电子温度,氧丰度等。氧丰度使用基于O3N2和R 23指标的两种经验方法得出,以及当氧饱和时采用直接方法得出。可用。通过将谐波分解分析应用于速度场,我们获得了视线旋转速度为71和位置角度为36°的结果。恒星年龄剖面显示,银河中心的恒星数量较大,而外围区域的恒星数量相对较年轻,这表明恒星年龄较大,而盘状星体较年轻。氧丰度分布在〜18 kpc处表现出明显的破裂,内部区域的梯度为?0.0364 dex kpc?1,外部区域的梯度为?0.00686 dex kpc?1。我们的结果与M101的“由内而外”磁盘增长情况一致。

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