The cosmological deceleration parameter estimated from the angular-size/redshift relation for compact radio sources
The cosmological deceleration parameter estimated from the angular-size/redshift relation for compact radio sources
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DOI：
10.1038/361134a0
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发表时间：
1993
期刊：
影响因子：
64.8
通讯作者：
K. Kellermann
中科院分区：
文献类型：
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作者：
K. Kellermann
在基于标准弗里德曼-罗伯逊-步行者几何的宇宙学模型中，标准烛光或标准棒的视通量密度或角尺寸以一种依赖于减速参数q 0的方式随红移而变化。(Open宇宙中的q 0 < 0.5;封闭宇宙中的q 0> 0.5。）然而，在低红移时，观测误差远大于不同宇宙学模型预期的q 0差异，而在高红移时，观测不确定性，特别是在光学波长处，以及源中明显的系统演化变化掩盖了预期的几何效应。在这里，我表明，甚长基线干涉测量（VLBI）的紧凑的无线电源与活跃的星系和类星体的测量可能在很大程度上没有进化的影响，即使在大量的红移。这些源的样本的角大小和红移之间的关系表明q 0值接近0.5，对应于临界值附近的宇宙学密度。
IN cosmological models based on the standard Friedmann–Robertson–Walker geometry, the apparent flux density or angular size of standard candles or standard rods varies with redshift in a way that depends on the deceleration parameterq0. (Open universes haveq0< 0.5; closed universes haveq0> 0.5.) At low redshift, however, observational errors are much greater than the differences inq0expected for different cosmological models, while at high redshift observational uncertainties, particularly at optical wavelengths, and apparent systematic evolutionary changes in sources obscure the expected geometrical effects. Here I show that measurements by very-long-baseline interferometry (VLBI) of compact radio sources associated with active galaxies and quasars may be largely free of evolutionary effects even at substantial redshifts. The relation between angular size and redshift for a sample of these sources indicates a value ofq0close to 0.5, corresponding to cosmological density near the critical value.