Abstract

The linear increase of the cosmic microwave background (CMB) temperature with cosmological redshift, \(T_{\textrm{CMB}}=T_{{0}}(1+z)\), is a prediction of the standard cosmological \(\Lambda\)CDM model. There are currently two methods to measure this dependence at redshift \(z>0\) and, what is equally important, to estimate of the CMB temperature \(T_{0}\) at the present epoch. The first method is based on the Sunyaev–Zeldovich effect for a galaxy cluster. However, this method is limited to redshifts \(z\lesssim 1\) and only the deviations from the standard relation can be measured with it. The second method is based on the analysis of the populations of atomic and molecular energy levels observed in the absorption spectra of quasars. This method allows \(T_{\textrm{CMB}}(z)\) to be measured directly. We present new estimates of \(T_{\textrm{CMB}}(z_{i})\) in the redshift range \(1.7\leq z_{i}\leq 3.3\) based on the analysis of the excitation of CO rotational levels and C I fine-structure levels in 15 absorption systems. We take into account the collisional excitation of CO and C I with hydrogen atoms and \(\textrm{H}_{2}\) and the radiative pumping of C I by the interstellar ultraviolet radiation. Applying this corrections leads to a systematic decrease in the previously obtained estimates of \(T_{\textrm{CMB}}(z_{i})\) (for some systems the magnitude of the effect is \({\sim}10\%\)). Combining our measurements with the measurements of \(T_{\textrm{CMB}}(z)\) in galaxy clusters we have obtained a constraint on the parameter \(\beta=+0.010\pm 0.013\), which characterizes the deviation of the CMB temperature from the standard relation, \(T_{\textrm{CMB}}=T_{{0}}(1+z)^{1-\beta}\), and an independent estimate of the CMB temperature at the present epoch, \(T_{0}=2.719\pm 0.009\) K, which agrees well with the estimate from orbital measurements, \(T_{0}=2.7255\pm 0.0006\) K.

中文翻译：

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从早期星系星际介质中的原子CI和分子CO线估算宇宙微波背景温度。

摘要

宇宙微波本底（CMB）温度随宇宙学红移的线性增加\（T _ {\ textrm {CMB}} = T _ {{{0}}（1 + z）\）是对标准宇宙学\（ \ Lambda \） CDM模型。当前有两种方法可以测量在红移\（z> 0 \）时的这种依赖性，并且同等重要的是，在当前时期估计CMB温度\（T_ {0} \）。第一种方法基于星系团的Sunyaev–Zeldovich效应。但是，此方法仅限于红移\（z \ lesssim 1 \）并且只能使用它来测量与标准关系的偏差。第二种方法是基于对类星体吸收光谱中观察到的原子和分子能级总体的分析。此方法允许直接测量\（T _ {\ textrm {CMB}}（z）\）。基于对CO激发的分析，我们给出了红移范围\（1.7 \ leq z_ {i} \ leq 3.3 \）中\（T _ {\ textrm {CMB}}（z_ {i}）\）的新估计值15个吸收系统中的旋转能级和CI精细结构能级。我们考虑到CO和C I与氢原子和\（\ textrm {H} _ {2} \）的碰撞激发以及星际紫外线辐射对C I的辐射泵浦。应用此更正会导致先前获得的\（T _ {\ textrm {CMB}}（z_ {i}）\）的估计值有系统地减少（对于某些系统，影响的大小为\（{\ sim} 10 \ ％\））。将我们的测量值与星系团中\（T _ {\ textrm {CMB}}（z）\）的测量值结合起来，我们获得了对参数\（\ beta = + 0.010 \ pm 0.013 \）的约束，该约束表征了偏差通过标准关系\（T _ {\ textrm {CMB}} = T _ {{{0}}（1 + z）^ {1- \ beta} \得出的CMB温度以及CMB温度在以下位置的独立估计当前时代\（T_ {0} = 2.719 \ pm 0.009 \）K，它与轨道测量的估计值非常吻合\（T_ {0} = 2.7255 \ pm 0.0006 \） K。