We analyzed the distribution of the red clump (RC) stars throughout the Galactic bulge using Two Micron All Sky Survey data. We mapped the position of the RC in 1?deg2 fields within the area |l| ≤ 85 and 35 ≤ |b| ≤ 85, for a total of 170?deg2. The single RC seen in the central area splits into two components at high Galactic longitudes in both hemispheres, produced by two structures at different distances along the same line of sight. The X-shape is clearly visible in the Z-X plane for longitudes close to the l = 0° axis. Crude measurements of the space densities of RC stars in the bright and faint RC populations are consistent with the adopted RC distances, providing further supporting evidence that the X-structure is real, and that there is approximate front-back symmetry in our bulge fields. We conclude that the Milky Way bulge has an X-shaped structure within |l| 2°, seen almost edge-on with respect to the line of sight. Additional deep near-infrared photometry extending into the innermost bulge regions combined with spectroscopic data is needed in order to discriminate among the different possibilities that can cause the observed X-shaped structure.
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机译：我们使用“两微米全天候测量”数据分析了整个银河凸起中红团（RC）星的分布。我们在| l |区域内的1？deg2场中绘制了RC的位置。 ≤85和35≤| b | ≤85，共170？deg2。在中央区域看到的单个RC在两个半球中以高银河经度分为两个部分，这是由两个结构沿同一视线以不同距离产生的。 X形在Z-X平面中清晰可见，其经度接近l = 0°轴。明亮和暗淡的RC种群中RC恒星的空间密度的粗略测量与所采用的RC距离一致，从而进一步证明X结构是真实的，并且在我们的凸起区域中存在近似前后对称性。我们得出结论，银河系凸起在| l |内具有X形结构。 2°，相对于视线几乎是直视的。为了区分可能导致观察到的X形结构的不同可能性，需要额外的深红外测光法并扩展到最里面的凸起区域，并结合光谱数据。
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