Local stellar kinematics from Hipparcos data
Local stellar kinematics from Hipparcos data
复制标题
DOI：
10.1046/j.1365-8711.1998.01600.x
复制
发表时间：
1998-08-01
影响因子：
4.8
通讯作者：
Binney, JJ
中科院分区：
文献类型：
--
作者：
Dehnen, W;Binney, JJ
根据依巴谷星表运动学无偏子样本的视差和自行运动，我们重新确定了主序星的运动学作为颜色的函数。虽然恒星平均日心速度的径向和垂直分量没有显示出颜色趋势，但银河系旋转方向的分量很好地遵循非对称漂移关系，除了比 B - V = 0.1 mag 更蓝的恒星之外。外推到零色散率，对于相对于当地静止标准 (LSR) 的太阳速度（以 km s(-1) 为单位），U-0 = 10.00 +/- 0.36（径向向内），V-0 = 5.25 +/- 0.62（沿银河系旋转方向）和 W-0 = 7.17 +/- 0.38（垂直向上）。在速度色散与颜色的关系图中可以清楚地看到不连续性：色散对于后期光谱类型来说基本上是恒定的，朝着 B - V 的早期光谱类型向蓝方向减小，大约为 0.61 mag。我们将速度色散张量 sigma(2) 确定为颜色的函数。涉及垂直运动的混合力矩在误差范围内为零，而 sigma(xy)(2) 在大约 (10 km s(-1))(2) 处不为零，与颜色无关。由此产生的顶点偏差对于早期型恒星来说约为 20 度，对于老盘恒星来说约为 10 度+/- 4。晚型恒星顶点偏差的持续存在意味着银河系势在太阳半径处显着非轴对称。如果旋臂是非轴对称性的原因，则它们不能紧密缠绕。除了比 B - V = 0.1 mag 更蓝的恒星外，主速度色散的比率由 sigma(1):sigma(2):sigma(3) 给出，近似为 2.2:1.4:1，而绝对值随着颜色的增加从 sigma(1) 近似增加到 B - V = 20 km s(-1)。 0.2 mag 至 sigma(1) 在帕雷纳戈不连续面及以上大约为 38 km s(-1)。这些比率意味着螺旋结构对盘的显着加热，并且R-0/R-d类似于或等于3至3.5，其中R-d是盘的标度长度。
From the parallaxes and proper motions of a kinematically unbiased subsample of the Hipparcos Catalogue, we have re-determined as a function of colour the kinematics of main-sequence stars.Whereas the radial and vertical components of the mean heliocentric velocity of stars show no trend with colour, the component in the direction of Galactic rotation nicely follows the asymmetric drift relation, except for stars bluer than B - V = 0.1 mag. Extrapolating to zero dispersion yields, for the velocity of the Sun with respect to the local standard of rest (LSR) in km s(-1), U-0 = 10.00 +/- 0.36 (radially inwards), V-0 = 5.25 +/- 0.62 (in the direction of Galactic rotation) and W-0 = 7.17 +/- 0.38 (vertically upwards).Parenago's discontinuity is beautifully visible in a plot of velocity dispersion against colour: the dispersion, which is essentially constant for late spectral types, decreases towards early spectral types blueward of B - V approximate to 0.61 mag.We determine the velocity dispersion tensor sigma(2) as function of colour. The mixed moments involving vertical motion are zero within the errors, while sigma(xy)(2) is non-zero at about (10 km s(-1))(2) independently of colour. The resulting vertex deviations are about 20 degrees for early-type stars and 10 degrees +/- 4 for old-disc stars. The persistence of the vertex deviation to late-type stars implies that the Galactic potential is significantly non-axisymmetric at the solar radius. If spiral arms are responsible for the non-axisymmetry, they cannot be tightly wound.Except for stars bluer than B - V = 0.1 mag, the ratios of the principal velocity dispersions are given by sigma(1):sigma(2):sigma(3) approximate to 2.2:1.4:1, while the absolute values increase with colour from sigma(1) approximate to 20 km s(-1) at B - V = 0.2 mag to sigma(1) approximate to 38 km s(-1) at Parenago's discontinuity and beyond. These ratios imply significant heating of the disc by spiral structure and that R-0/R-d similar or equal to 3 to 3.5, where R-d is the scalelength of the disc.