最小非线性哈勃膨胀变分框架的定义
Defining the frame of minimum nonlinear Hubble expansion variation
摘要：
我们描述了一个宇宙静止框架中的球平均的非线性哈勃膨胀是最均匀的，在任意的本地洛伦兹提升的中央观察者。利用4534个星系的COMPOSITE样本，我们确定了一组退化的候选最小非线性变化框架，其中包括本星系群（LG）的静止框架，但不包括标准的宇宙微波背景（CMB）框架。候选静止帧由LG帧的提升定义，接近星系平面，具有与LG帧相似的统计可能性。这可能是由于回避区缺乏约束数据造成的。我们将我们的分析扩展到8162个星系的宇宙流-2（CF2）样本。虽然仍然检测到CMB和LG帧平均值之间的系统增强偏移的签名，但是所有其余帧中的球面平均非线性扩展变化在CF 2样本中显著大于合理预期。我们追踪到CF2距离报告没有校正非均匀分布Malmquist偏差。系统的差异，包括大SFI++子样本到复合材料和CF2目录进行了分析。我们的研究结果强调了仔细处理Malmquist偏差对未来特殊速度研究的重要性，包括Wiltshire等人[Phys. Rev. D 88（2013）083529; arXiv：1201.5371]假设的检验，即CMB温度偶极子的很大一部分可能是非运动学起源的。
英文摘要：
We characterize a cosmic rest frame in which the monopole variation of the spherically averaged nonlinear Hubble expansion is most uniform, under arbitrary local Lorentz boosts of the central observer. Using the COMPOSITE sample of 4534 galaxies, we identify a degenerate set of candidate minimum nonlinear variation frames, which includes the rest frame of the Local Group (LG) of galaxies, but excludes the standard Cosmic Microwave Background (CMB) frame. Candidate rest frames defined by a boost from the LG frame close to the plane of the galaxy have a statistical likelihood similar to the LG frame. This may result from a lack of constraining data in the Zone of Avoidance. We extend our analysis to the Cosmicflows-2 (CF2) sample of 8162 galaxies. While the signature of a systematic boost offset between the CMB and LG frame averages is still detected, the spherically averaged nonlinear expansion variation in all rest frames is significantly larger in the CF2 sample than would be reasonably expected. We trace this to the CF2 distances being reported without a correction for inhomogeneous distribution Malmquist bias. Systematic differences in the inclusion of the large SFI++ subsample into the COMPOSITE and CF2 catalogues are analysed. Our results highlight the importance of a careful treatment of Malmquist biases for future peculiar velocities studies, including tests of the hypothesis of Wiltshire et al [Phys. Rev. D 88 (2013) 083529; arXiv:1201.5371] that a significant fraction of the CMB temperature dipole may be nonkinematic in origin.
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