Evolution of Galaxies and Observational Cosmology

通过在理论框架中引入探测和选择效应，对暗星系的数量和红移分布进行了宇宙学预测。结果表明，给定视星等星系的发现率强烈依赖于探测判据和星等测量算法，在最近的星系调查中，大量高红移的暗星系应该是没有被探测到的。利用现有的星系光度演化模型，在假设星系不演化的前提下，直接与B_J=27 MAG或相当深度的B_JR_FIK波段未修正的星系计数数据以及B_J=23 MAG的Durham红移分布作了比较。结果表明，具有非零宇宙学常数的平坦而低密度的omega_O-0.1宇宙可以解释所有的数据，而平坦且高密度的omega_O=1宇宙与所有的数据都有明显的差异。星系在数量和/或直径上的演化假说与微弱的观测结果相对照，得到了检验。与通常的预期相反，由星系合并驱动的数量演化不能协调观测到的B_J=27 MAG处的高计数和高密度的OMEGA_O=1宇宙，因为许多高红移的预合并不应该按照最近调查中采用的标准来计算。中心表面亮度与视星等的关系被发现只对星系的固有大小的变化很敏感，因此它被用作星系直径演化的探测器。预测关系和观测关系的比较表明，大多数星系在相当大一部分年龄内只经历了很小的直径演化。

Cosmological predictions of number count and redshift distribution of faint galaxies are made by incorporating detection and selection effects in the theoretical framework. It is shown that the detection rate for galaxies at given apparent magnitude strongly depends on the detection criterion and magnitude measurement algorithm, and that a large number of faint galaxies with high redshifts should remain undetected in recent galaxy surveys. By using a current model of galaxy luminosity evolution with the assumption that galaxies do not evolve in number or cliameter, the predictions are compared directly with the uncorrected B_JR_FIK-band galaxy count data reaching B_J = 27mag or the equivalent depth and also with the Durham redshift distribution to B_J = 23mag. It is concluded that a flat and low-density OMEGA_O - 0.1 universe with non-zero cosmological constant can account for all the data but a flat and high-density OMEGA_O = 1 universe shows a marked discrepancy with all the data. The hypothesis of galaxy evolution in number and/or diameter is tested against the faint observations. Contrary to usual expectations, a number evolution driven by galaxy mergers cannot reconcile the observed high count at B_J = 27mag and the high densityOMEGA_O = 1 universe because many high-redshift premergers should not be counted according to the criterion adopted in the recent surveys. The central surface brightness versus apparent magnitude relation is found to be sensitive solely to a change of intrinsic size of galaxies so that it is used as a probe of their diameter evolution. Comparison between the predicted and observed relations indicates that the bulk of galaxies have undergone very little diameter evolution over a considerable fraction of their age.