NGC 6503中非轴对称问题的研究
Searching for Non-axisymmetries in NGC 6503: A Weak End-on Bar
摘要：
邻近的螺旋星系NGC 6503的孤立、简单的视结构和低光度使其成为深入运动学和光度学研究的理想候选者。我们引入了一个新的公开代码，ESPFIT，实现非轴对称拟合的运动学或光度数据的程序。我们使用NGC Fit来分析新的Halpha和CO速度场数据以及Greisen等人的HI运动学，以搜索NGC 6503圆盘中的非圆运动。我们发现NGC 6503具有非常规则的气体运动学，仅用旋转就能很好地描述。我们还使用了NGC 6503的Ks波段图像来约束圆盘、棒和凸起的光度模型。我们发现星系在光度上受圆盘支配。我们发现NGC 6503包含一个微弱的酒吧和一个指数隆起，共同贡献只有~5%的总星系光。结合我们的运动学和光度学的拟合模型表明，NGC 6503包含一个弱的，端部的酒吧，可能已经产生了它的II型表面亮度轮廓，但不太可能是负责其强大的西格玛下降。
英文摘要：
The isolation, simple apparent structure, and low luminosity of the nearby spiral galaxy NGC 6503 make it an ideal candidate for an in-depth kinematic and photometric study. We introduce a new publicly available code, DiskFit, that implements procedures for fitting non-axisymmetries in either kinematic or photometric data. We use DiskFit to analyze new Halpha and CO velocity field data as well as HI kinematics from Greisen et al. to search for non-circular motions in the disc of NGC 6503. We find NGC 6503 to have remarkably regular gas kinematics that are well-described by rotation only. We also use DiskFit and a new Ks-band image of NGC 6503 to constrain photometric models of the disc, bar and bulge. We find the galaxy to be photometrically dominated by the disc. We find NGC 6503 to contain a faint bar and an exponential bulge which together contribute only ~5% of the total galaxy light. The combination of our kinematic and photometric DiskFit models suggest that NGC 6503 contains a weak, end-on bar that may have produced its Type II surface brightness profile but is unlikely to be responsible for its strong sigma-drop.
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