New light on faint stars – III. Galactic structure towards the South Pole and the Galactic thick disc
New light on faint stars – III. Galactic structure towards the South Pole and the Galactic thick disc
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DOI：
10.1093/mnras/202.4.1025
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发表时间：
1983-04
影响因子：
4.8
通讯作者：
G. Gilmore;N. Reid
中科院分区：
文献类型：
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作者：
G. Gilmore;N. Reid
我们已经从光度学视差中得到了∼12500颗恒星的绝对等级数，这些恒星在18.24平方度的范围内向南银河系极点的亮度为Thani=18。根据这些数据，我们得到了所有高于热核燃烧极限的绝对星等在太阳附近的绝对视星等、辐射热星等和质量方面的恒星光度函数。太阳附近主序星的总质量为0.038m⊙pc−3，总质量光比为1.2m⊙/Lv⊙，并导出了各绝对星等的密度随距银面距离的变化规律。恒星光度函数显示出一种系统的形状变化，与较暗的恒星相比，恒星更多地集中在平面上。恒星的密度定律服从标度高度为∼300pC的单一指数，以及标度高度为∼1450pC的第二个指数，标度高度从∼1000pc到至少5000pC。这第二个指数包含了太阳附近2%的恒星。我们确定300pC尺度的高度分量是旧的圆盘，1350pC尺度的高度分量是银河系的“厚盘”。厚盘的光度函数和密度定律与银盘引力势使球体等密度等高线明显变平是一致的，这与最近对几个外部星系的观测一致。
We have derived absolute magnitudes from photometric parallaxes for a complete sample of ∼ 12 500 stars brighter thanI= 18 in 18.24 square degrees towards the South Galactic Pole. From these data we derive the stellar luminosity function in absolute visual magnitude, bolometric magnitude and mass in the solar neighbourhood for all absolute magnitudes above the thermonuclear burning limit. The total mass in main-sequence stars in the solar neighbourhood is 0.038m⊙pc−3, and the total mass-to-light ratio is 1.2 (m⊙/Lv⊙).We have also derived the density laws with distance from the Galactic plane for each absolute magnitude. The stellar luminosity function shows a systematic change in shape, with stars withsubstantially more concentrated to the plane than fainter stars. The density laws for stars withfollow a single exponential with scale height ∼ 300 pc for, and a second exponential with scale height ∼ 1450 pc forzdistances from ∼ 1000 to at least 5000 pc. This second exponential contains ∼ 2 per cent of the stars in the solar neighbourhood.We identify the 300 pc scale height component as old disc, and the 1350 pc scale height component as a Galactic ‘thick disc’. The luminosity function and density law of the ‘thick disc’ are consistent with substantial flattening of the spheroid isodensity contours by the gravitational potential of the Galactic disc, in agreement with recent observations of several external galaxies.