s model is based on the section II B <a class="reference external" href="https://arxiv.org/pdf/2204.11864.pdf">Ng et al. 2022</a> paper.</p></li>
<li><p>Its a phenomenological model for the volumetric merger rate density of Pop III BBHs.</p></li>
<li><p>This model is a simple fit to the merger rate density predicted from population synthesis studies.</p></li>
</ul>
<p><span class="math">\begin{equation}
\dot{n}_{III} = n_o \frac{e^{a_{III}(z_s-z_{III})}}{a_{III}+b_{III} e^{(a_{III}+b_{III})(z_s-z_{III})}} \