The low dark matter content of the lenticular galaxy NGC 3998
The low dark matter content of the lenticular galaxy NGC 3998
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DOI：
10.1093/mnras/stw1187
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发表时间：
2016-05
影响因子：
4.8
通讯作者：
N. Boardman;A. Weijmans;R. V. D. Bosch;L. Zhu;A. Yıldırım;G. Ven;M. Cappellari;P. Zeeuw;E. Emsellem;D. Krajnovi'c;T. Naab
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作者：
N. Boardman;A. Weijmans;R. V. D. Bosch;L. Zhu;A. Yıldırım;G. Ven;M. Cappellari;P. Zeeuw;E. Emsellem;D. Krajnovi'c;T. Naab
我们用米切尔积分场光谱仪对透镜状星系NGC 3998进行了观测，提取了3个半光半径范围内的视距速度分布。我们利用Mitchell和SAURON仪器的运动学数据，构建了无碰撞轨道模型，以约束NGC 3998的黑暗和可见结构。我们发现NGC 3998几乎是轴对称的，几乎面朝上，具有平坦的内在形状——也就是说，一个面朝上的快速旋转体。我们发现这个星系的i波段质量光比为4.7_{-0.45}^{+0.32}$，与之前的光谱拟合结果非常吻合。我们最适合的轨道模型显示了一个凸起和一个圆盘的成分，一个不可忽略的反向旋转成分也很明显。我们发现相对较少的暗物质需要建立这个星系的模型，推断出的暗质量分数仅为$(7.1^{+8.1}_{-7.1})\%$，在一个半光半径内。
We observed the lenticular galaxy NGC 3998 with the Mitchell Integral-Field Spectrograph and extracted line-of-sight velocity distributions out to 3 half-light radii. We constructed collisionless orbit models in order to constrain NGC 3998's dark and visible structure, using kinematics from both the Mitchell and SAURON instruments. We find NGC 3998 to be almost axisymmetric, seen nearly face on with a flattened intrinsic shape - i.e., a face-on fast-rotator. We find an I-band mass-to-light ratio of $4.7_{-0.45}^{+0.32}$ in good agreement with previous spectral fitting results for this galaxy. Our best-fit orbit model shows a both a bulge and a disc component, with a non-negligible counter-rotating component also evident. We find that relatively little dark matter is needed to model this galaxy, with an inferred dark mass fraction of just $(7.1^{+8.1}_{-7.1})\%$ within one half-light radius.