星系大尺度本动速度

Large Scale Peculiar Velocities of Galaxies

本文从高斯型的初始质量密度扰动出发,采用球对称演化模型计算了星系大尺度本动速度随尺度的分布。采用这样一种模型可以避免通常流体模型中线性增长以及窗函数的假设,对不同的宇宙物质主导成分的讨论表明,在各种情况下本动速度的期待值v_p在大尺度上的分布是随着尺度的增大而逐渐减小,这与流体模型以及宇宙弦模型下的趋势是一致的,但对所有参数的可能取值所作的计算表明,理论结果很难解释Dressler等人在r～60h^(-1)Mpc的尺度上观测到的大的本动速度,这很可能是由于在本星系群(LG)之外r 60h^(-1)Mpc的远处存在着一个大质量的物质凝聚区域。

Assuming Gaussian primordial mass perturbation and spherical symmetry, a detailed calculation of the distribution of large scale peculiar velocities is presented. Our method avoids the linear perturbation approximation and window functions which are widely used in the fluid models. We get expected values of the peculiar velocities in several models of universe dominated by different kinds of cosrnological matter. The expected values of peculiar velocities of galaxies decrease with the increase of distance scale. This trend is in agreement with what conventional fluid and cosmic string models predict. Considering acceptable values of all parameters, we conclude that our method is unable to explain the observed high peculiar velocities on a scale of 60 h-1 Mpc reported by Dressier et al. in 1987. A reasonable explanation for the disagreement between observation and theory is that there may be a huge mass-concentration region out to a distance of r≥60h-1 Mpc away from the Local Group.