text{yr}^{-1} \tag{4}
\end{equation}</span></p>
<ul class="simple">
<li><p><span class="math notranslate nohighlight">\(z_s\)</span>: redshift of source</p></li>
<li><p><span class="math notranslate nohighlight">\(n_o\)</span>: Normalization factor. <span class="math notranslate nohighlight">\(t_o\)</span> is the present age of the Universe.</p></li>
<li><p><span class="math notranslate nohighlight">\(n_o=0.044\times 10^{-9}\)</span>, <span class="math notranslate nohighlight">\(t_o=13.786885302009708\)</sp