Atlas3D项目- XII。用轴对称动力学模型恢复模拟早型棒星系的质光比
The Atlas3D project - XII. Recovery of the mass-to-light ratio of simulated early-type barred galaxies with axisymmetric dynamical models
摘要：
我们调查的准确性恢复的恒星动力学的棒星系时，使用轴对称动力学模型。我们这样做，试图恢复质光比（M/L）和各向异性的现实星系模拟使用牛仔各向异性多高斯展开（JAM）方法。然而，考虑到我们发现的偏差主要是由于应用的轴对称建模算法的非轴对称系统，特别是在去投影质量模型的不准确性，我们的结果是相关的一般轴对称建模方法。我们运行N体无碰撞模拟，以建立一个具有各种光度分布的库，构造来模拟真实的单个星系，具有现实的各向异性。我们进化的模拟库的最终结果包含了棒星系和无棒星系。JAM方法假设轴对称质量分布，我们采用空间常数M/L和各向异性β_z=1-sigma_z^2/sigma_R^2分布。这些模型被拟合到不同视角（棒的位置角和星系的倾角）下模拟的二阶速度矩V_rms=sqrt（V^2+sigma^2）的二维图上。我们发现，倾斜度一般是很好地恢复的JAM模型，禁止和unbarred模拟。对于无限制的模拟，M/L也被准确地恢复，中值偏差可以忽略不计，当星系不是太靠近而不能面对时，最大值仅为Delta（M/L）<1.5%。在非常低的倾角（i<30度）下，M/L可能被显著高估（在我们的测试中为9%，但对于非常正面的视图，误差可能更大）。对于禁止模拟，M/L平均（当PA=45度时）基本上是无偏的，但我们在测试中测量了高达Delta（M/L）=15%的过/欠估计。M/L偏差的符号取决于预期的杆的位置角。[删节]
英文摘要：
We investigate the accuracy in the recovery of the stellar dynamics of barred galaxies when using axisymmetric dynamical models. We do this by trying to recover the mass-to-light ratio (M/L) and the anisotropy of realistic galaxy simulations using the Jeans Anisotropic Multi-Gaussian Expansion (JAM) method. However, given that the biases we find are mostly due to an application of an axisymmetric modeling algorithm to a non-axisymmetric system and in particular to inaccuracies in the de-projected mass model, our results are relevant for general axisymmetric modelling methods. We run N-body collisionless simulations to build a library with various luminosity distribution, constructed to mimic real individual galaxies, with realistic anisotropy. The final result of our evolved library of simulations contains both barred and unbarred galaxies. The JAM method assumes an axisymmetric mass distribution, and we adopt a spatially constant M/L and anisotropy beta_z=1-sigma_z^2/sigma_R^2 distributions. The models are fitted to two-dimensional maps of the second velocity moments V_rms=sqrt(V^2+sigma^2) of the simulations for various viewing angles (position angle of the bar and inclination of the galaxy). We find that the inclination is generally well recovered by the JAM models, for both barred and unbarred simulations. For unbarred simulations the M/L is also accurately recovered, with negligible median bias and with a maximum one of just Delta(M/L)<1.5% when the galaxy is not too close to face on. At very low inclinations (i<30 deg) the M/L can be significantly overestimated (9% in our tests, but errors can be larger for very face-on views). For barred simulations the M/L is on average (when PA=45 deg) essentially unbiased, but we measure an over/under estimation of up to Delta(M/L)=15% in our tests. The sign of the M/L bias depends on the position angle of the bar as expected. [Abridged]
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