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首页> 外文期刊>The Astrophysical journal >A TWO MICRON ALL SKY SURVEY VIEW OF THE SAGITTARIUS DWARF GALAXY. III. CONSTRAINTS ON THE FLATTENING OF THE GALACTIC HALO
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A TWO MICRON ALL SKY SURVEY VIEW OF THE SAGITTARIUS DWARF GALAXY. III. CONSTRAINTS ON THE FLATTENING OF THE GALACTIC HALO

机译：射手座星系银河的两张微缩全景视图。三，约束银河晕的飘动

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摘要

M giants selected from the Two Micron All Sky Survey (2MASS) have been used to trace streams of tidal debris apparently associated with the Sagittarius dwarf spheroidal galaxy (Sgr) that entirely encircle the Galaxy. While the Sgr M giants are generally aligned with a single great circle on the sky, we measure a difference of 10°.4 ± 2°.6 between the mean orbital poles of the great circles that best fit debris leading and trailing Sgr, which can be attributed to the precession of Sgr's orbit over the range of phases explored by the data set. Simulations of the destruction of Sgr in potentials containing bulge, disk, and halo components best reproduce this level of precession along the same range of orbital phases if the potential contours of the halo are only slightly flattened, with the ratio of the axis length perpendicular to and in the disk in the range q = 0.90-0.95 (corresponding to isodensity contours with q_ρ ～ 0.83—0.92). Oblate halos are strongly preferred over prolate (q_ρ > 1) halos, and flattenings in the potential of q ≤ 0.85 (q_ρ ≤ 0.75) and q ≥ 1.05 (q_ρ ≥ 1.1) are ruled out at the 3 σ level. More extreme values of q ≤ 0.80 (q_ρ ≤ 0.6) and q ≥ 1.25 (q_ρ ≥ 1.6) are ruled out at the 7 and 5 σ levels, respectively. These constraints will improve as debris with larger separation in orbital phases is found.
机译：从“两微米全天候调查”（2MASS）中选出的M个巨人已被用来追踪潮汐碎片流，这些潮汐流显然与人马座矮球体星系（Sgr）完全围绕着银河系有关。尽管Sgr M巨人通常与天空中的单个大圆圈对齐，但我们测量出最适合碎片前导和尾随Sgr的大圆圈的平均轨道极之间的差为10°.4±2°.6可以归因于Sgr轨道在数据集探索的阶段范围内的进动。如果晕轮的电势轮廓仅稍微变平，且轴长与垂直轴的比例垂直在圆盘中，q的范围为q = 0.90-0.95（对应于等密度线，q_ρ〜0.83-0.92）。扁圆形晕圈优于扁圆形晕圈（q_ρ> 1），并且在3σ级别排除了q≤0.85（q_ρ≤0.75）和q≥1.05（q_ρ≥1.1）势能的展平。在7和5σ级别分别排除q≤0.80（q_ρ≤0.6）和q≥1.25（q_ρ≥1.6）的更极端值。当发现在轨道相中具有较大间隔的碎片时，这些约束条件将得到改善。

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