Spectroscopic Survey of Red Giants in the SMC . I : Kinematics 1
Spectroscopic Survey of Red Giants in the SMC . I : Kinematics 1
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SMC 中红巨星的光谱调查。
DOI：
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发表时间：
2021
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通讯作者：
J. Harris
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作者：
J. Harris
我们对分布在小麦哲伦星云(SMC)中央4kpc×2kpc的2046颗红巨星进行了光谱观测。经过拟合和剔除横跨SMC(北纬10 E，S角7.9公里)的一个小速度梯度后，我们测量到S的均方根速度散射为27.5±0.5公里，视线速度分布符合高斯分布，速度弥散分布随半径变化几乎为常数。我们没有发现潮汐扰动的运动学证据。如果没有对SMC本身运动的高精度测量，就不可能根据我们测量的径向速度梯度来约束SMC的真实旋转速度。然而，即使在保守的假设下，我们也发现v<；σ，因此SMC主要由其速度弥散来支撑。我们发现，通过对其红巨星的空间分布的分析，星云中心的形状与在允许的v/σ值范围内预期的旋转平坦度是一致的。因此，SMC的性质与类似的低光度球体系统一致。我们的结论是，SMC主要是一个低光度的球体，其不规则的视觉外观是由新星形成所主导的。使用测量的运动学进行简单的维里分析表明，封闭质量在1.4kpc到1.9x10m⊙之间，而约束较差的质量在3kpc之间，在2.7x10m⊙之间。主题词：星系：进化--星系：恒星含量--星系：麦哲伦云--星系：个体：小麦哲伦星云本文包含了智利拉斯坎帕纳斯天文台6.5米麦哲伦望远镜收集的数据。
We present a spectroscopic survey of 2046 red giant stars, distributed over the central 4 kpc×2 kpc of the Small Magellanic Cloud (SMC). After fitting and removing a small velocity gradient across the SMC (7.9 km s deg oriented at 10 E of N), we measure an rms velocity scatter of 27.5 ± 0.5 km s. The line of sight velocity distribution is well-characterized by a Gaussian and the velocity dispersion profile is nearly constant as a function of radius. We find no kinematic evidence of tidal disturbances. Without a high-precision measurement of the SMC’s proper motion, it is not possible to constrain the SMC’s true rotation speed from our measured radial-velocity gradient. However, even with conservative assumptions, we find that v < σ and hence that the SMC is primarily supported by its velocity dispersion. We find that the shape of the SMC, as measured from the analysis of the spatial distribution of its red giant stars, is consistent with the degree of rotational flattening expected for the range of allowed v/σ values. As such, the properties of the SMC are consistent with similar low luminosity spheroidal systems. We conclude that the SMC is primarily a low luminosity spheroid whose irregular visual appearance is dominated by recent star formation. A simple virial analysis using the measured kinematics implies an enclosed mass within 1.6 kpc of between 1.4 and 1.9× 10M⊙, and a less well constrained mass within 3 kpc of between 2.7 and 5.1× 10M⊙. Subject headings: galaxies: evolution — galaxies: stellar content — galaxies: Magellanic Clouds — galaxies: individual: Small Magellanic Cloud This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.