涡度对盘方向影响的探测
Detection of the Vorticity Effect on the Disk Orientations
摘要：
我们给出了涡度对星系角动量非线性演化的影响的观测证据。我们首先计算涡度作为旋度的特殊速度场重建从2MASS红移调查。然后，通过测量涡度场和潮汐剪切场之间的对齐，我们研究了对齐的强度和趋势如何依赖于宇宙网环境。结果发现，在结和细丝区域的涡量矢量是反对齐的最大体积压缩的方向，而在空隙和片区域，他们是反对齐的最小压缩的方向。通过对Sloan数字巡天第七次数据发布中邻近的大面盘星系和大边盘星系的自旋轴的测定，并测量它们与星系位置涡度矢量的相关性，我们最终发现了星系自旋与局部涡度场之间的一致性信号。在99.999%的置信水平下，拒绝了它们之间不存在对齐的零假设。我们的结果支持观测最近提出的方案，虽然星系角动量起源于初始潮汐相互作用的线性制度，其随后的演变主要是由宇宙涡度场驱动。
英文摘要：
We present an observational evidence for the vorticity effect on the nonlinear evolution of the galaxy angular momentum. We first calculate the vorticity as the curl of the peculiar velocity field reconstructed from the 2MASS redshift survey. Then, measuring the alignments between the vorticity and the tidal shear fields, we study how the alignment strength and tendency depends on the cosmic web environment. It is found that in the knot and filament regions the vorticity vectors are anti-aligned with the directions of the maximal volume compression while in the void and sheet regions they are anti-aligned with the directions of the minimal compression. Determining the spin axes of the nearby large face-on and edge-on disk galaxies from the Seventh Data Release of the Sloan Digital Sky Survey and measuring their correlations with the vorticity vectors at the galaxy positions, we finally detect a clear signal of the alignments between the galaxy spin and the local vorticity fields. The null hypothesis that there is no alignment between them is rejected at the 99.999% confidence level. Our result supports observationally the recently proposed scenario that although the galaxy angular momentum originates from the initial tidal interaction in the linear regime its subsequent evolution is driven primarily by the cosmic vorticity field.
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