Self-consistent Response of a Galactic Disk to an Elliptical Perturbation Halo Potential
Self-consistent Response of a Galactic Disk to an Elliptical Perturbation Halo Potential
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银盘对椭圆扰动晕势的自洽响应
DOI：
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发表时间：
2000
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影响因子：
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通讯作者：
C. Jog
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文献类型：
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作者：
C. Jog
我们计算了轴对称星系盘受谐波数 m = 2 的椭圆晕势扰动的自洽响应，并获得了净盘椭圆率。通常预计这种潜力是由于星系潮汐相遇以及星系形成过程中而产生的。与盘的自洽、非轴对称密度响应相对应的自引力势是通过薄盘泊松方程的反演获得的。该响应电势被证明与扰动电势相反，因为盘的自重力在物理上抵抗了施加的电势。这导致盘平面中扰动光环势的净椭圆率减小。表示这种减少的减少因子与扰动势的强度无关，并且对于各种星系参数来说，其典型最小值约为 0.75-0.9。这种减少在 1.4 指数圆盘尺度长度时最为重要，而在较高半径时则逐渐减少。对于银河系的太阳邻域区域，折减系数为 0.8。超过霍姆伯格半径的两倍，减少量可以忽略不计，并且原子氢气中的圆盘不对称性追踪了晕势的真实椭圆率。对于晕电势的高次谐波 (m ≥ 3)，在所有半径处，减小量都可以忽略不计。在校正负盘响应时，典型螺旋星系晕位势的真实椭圆率比文献中根据盘的等光或运动学不对称性观测推导出的典型晕位椭圆率 ≤0.1 高约 20%。
We calculate the self-consistent response of an axisymmetric galactic disk perturbed by an elliptical halo potential of harmonic number m = 2 and obtain the net disk ellipticity. Such a potential is commonly expected to arise due to galactic tidal encounter and also during the galaxy formation process. The self-gravitational potential corresponding to the self-consistent, nonaxisymmetric density response of the disk is obtained by inversion of the Poisson equation for a thin disk. This response potential is shown to oppose the perturbation potential because physically the disk self-gravity resists the imposed potential. This results in a reduction in the net ellipticity of the perturbation halo potential in the disk plane. The reduction factor denoting this decrease is independent of the strength of the perturbation potential and has a typical minimum value of ~0.75-0.9 for a wide range of galaxy parameters. The reduction is most important at 1.4 exponential disk scale lengths and is progressively less so at higher radii. For the solar neighborhood region of the Galaxy, the reduction factor is 0.8. Beyond twice the Holmberg radius, the reduction is negligible, and there the disk asymmetry in the atomic hydrogen gas traces the true ellipticity of the halo potential. The reduction is negligible at all radii for higher harmonics (m ≥ 3) of the halo potential. On correcting for the negative disk response, the true ellipticity of the halo potential for a typical spiral galaxy is shown to be higher by ~20% than the typical halo ellipticity of ≤0.1 deduced in the literature from observations of isophotal or kinematical asymmetry of disks.