The Rotating Nuclear Star Cluster in NGC 4244
The Rotating Nuclear Star Cluster in NGC 4244
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DOI：
10.1088/0004-637x/693/2/1959
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发表时间：
2008-07
期刊：
影响因子：
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通讯作者：
A. Seth;R. Blum;N. Bastian;N. Caldwell;V. Debattista
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文献类型：
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作者：
A. Seth;R. Blum;N. Bastian;N. Caldwell;V. Debattista
我们用带有激光导星自适应光学的双子座近红外积分场光谱仪对附近的边缘螺旋星系NGC4244中的核星团进行了观测。从以前对边缘星系的研究中，这个核星团被发现是沿着其所在星系盘平面看起来扁平的星系团样本之一。这样的星团显示了多种形态成分的证据，其中有较年轻/较蓝色的圆盘成分和较老/较红的球状成分。我们对NGC4244的新观测表明，在星系团的中心10PC(0.5“)内，S−1清晰地自转了30公里。中心速度色散为28±2 km S−1。从光学颜色和光谱中推断的多恒星群被看作是NIFS谱中CO谱线强度的变化。即使在更老的、更球状的恒星成分中，也能清楚地检测到自转。我们讨论了包括M33和银河系在内的其他星系的核星团中类似结构和运动学的证据。我们的观测支持两种可能的形成机制：(1)来自盘状气体的幕式吸积直接进入核星团；或(2)由于动力摩擦而在星系中心形成的年轻星团的幕式吸积。
We present observations of the nuclear star cluster in the nearby edge-on spiral galaxy NGC 4244 using the Gemini Near-Infrared Integral Field Spectrograph (NIFS) with laser guide star adaptive optics. From a previous study of edge-on galaxies, this nuclear star cluster was found to be one of a sample of clusters that appear flattened along the plane of their host galaxies disks. Such clusters show evidence for multiple morphological components, with younger/bluer disk components and older/redder spheroidal components. Our new observations of NGC 4244 show clear rotation of 30 km s−1 within the central 10 pc (0.5″) of the cluster. The central velocity dispersion is found to be 28 ± 2 km s−1. The multiple stellar populations inferred from the optical colors and spectra are seen as variations in the CO line strength in the NIFS spectra. The rotation is clearly detected even in the older, more spheroidal stellar component. We discuss evidence for similar structures and kinematics in the nuclear star clusters of other galaxies including M33 and the Milky Way. Our observations support two possible formation mechanisms: (1) episodic accretion of gas from the disk directly onto the nuclear star cluster; or (2) episodic accretion of young star clusters formed in the central part of the galaxy due to dynamical friction.