Axisymmetric orbit models of N-body merger remnants: a dependency of reconstructed mass on viewing angle
Axisymmetric orbit models of N-body merger remnants: a dependency of reconstructed mass on viewing angle
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DOI：
10.1111/j.1365-2966.2007.12343.x
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发表时间：
2007-08
影响因子：
4.8
通讯作者：
J. Thomas;R. Jesseit;T. Naab;R. Saglia;A. Burkert;R. B. U. Munich;Mpe Garching
中科院分区：
文献类型：
--
作者：
J. Thomas;R. Jesseit;T. Naab;R. Saglia;A. Burkert;R. B. U. Munich;Mpe Garching
我们模拟观察碰撞N体盘盘合并与相同的轴对称轨道叠加程序，已被用来模拟椭圆星系后发座。残留物样品代表了盘-盘合并的形状分布，包括最极端的情况，如高度长球形，最大三轴和主要扁球形物体。我们的研究的目的是更好地了解轴对称的假设如何影响重建的质量和恒星运动的系统，本质上不是轴对称的，是否轴对称的假设，然后导致一个偏见，以及如何这样的潜在的偏见可以在真实的星系的模型中识别。在半光半径的质量恢复取决于视角和内在的形状：边缘视图允许重建总质量的精度在20%（三轴/长轴残余物）和3%（扁圆残余物）之间。高度扁平、正面系统的质量被低估达50%。在残留物为强三轴或扁长的地方，局部质量密度的偏差可能更大。发光的质光比对残骸中的盒子轨道很敏感。盒轨道导致高斯-厄米特参数H4的中心值随视角而变化。重建的发光质光比，以及重建的中心质量，遵循这种变化。发光的质光比总是被低估（高达2.5倍）。模型中的暗晕可能会被高估大约相同的量，这再次取决于视角。重建的速度各向异性英尺取决于视角，以及对轨道组成的残余物，大多是准确的约A/？= 0.2。较大的偏差可以分别朝向中心或外部区域发生。我们构造了史瓦西模型的N体实现，讨论了模型中的混沌轨道和维里平衡。在这项研究中，我们探讨了轴对称模型的极限。表面上扁平的、中等质量的旋转椭圆星系很可能既接近于轴对称，又接近于边缘取向。我们的研究结果表明，史瓦西模型允许重建它们的质量和恒星各向异性的高精度。
We model mock observations of collisionless N-body disc-disc mergers with the same axisymmetric orbit superposition program that has been used to model elliptical galaxies in Coma. The remnants sample representatively the shape distribution of disc-disc mergers, including the most extreme cases, like highly prolate, maximally triaxial and dominantly oblate objects. The aim of our study is to better understand how the assumption of axial symmetry affects reconstructed masses and stellar motions of systems which are intrinsically not axisymmetric, whether the axisymmetry assumption then leads to a bias and how such a potential bias can be recognized in models of real galaxies. The mass recovery at the half-light radius depends on viewing angle and intrinsic shape: edge-on views allow to reconstruct total masses with an accuracy between 20 per cent (triaxial/prolate remnants) and 3 per cent (oblate remnant). Masses of highly flattened, face-on systems are underestimated by up to 50 per cent. Deviations in local mass densities can be larger where remnants are strongly triaxial or prolate. Luminous mass-to-light ratios are sensitive to box orbits in the remnants. Box orbits cause the central value of the Gauss-Hermite parameter H 4 to vary with viewing angle. Reconstructed luminous mass-to-light ratios, as well as reconstructed central masses, follow this variation. Luminous mass-to-light ratios are always underestimated (up to a factor of 2.5). Respective dark haloes in the models can be overestimated by about the same amount, depending again on viewing angle. Reconstructed velocity anisotropies ft depend on viewing angle as well as on the orbital composition of the remnant and are mostly accurate to about A/? = 0.2. Larger deviations can occur towards the centre or the outer regions, respectively. We construct N-body realizations of the Schwarzschild models to discuss chaotic orbits and the virial equilibrium in our models. In this study we explore the extreme limits of axisymmetric models. Apparently flattened, rotating ellipticals of intermediate mass are likely close to both, axial symmetry and edge-on orientation. Our results imply that Schwarzschild models allow a reconstruction of their masses and stellar anisotropies with high accuracy.