><td><p>Primordial black holes</p></td>
<td><p>Unknown, expected to have a power-law dependence on the age of the Universe</p></td>
<td><p>Expected to be higher at high redshifts</p></td>
</tr>
</tbody>
</table>
<ul class="simple">
<li><p>The BBH merger density distribution from Pop I/II stars is well-studied, while the BBH merger density distribution from Pop III stars and PBHs is much less well-studied.</p></li>
<li><p>Astronomers are interested in studying the BBH merger density distribution from Pop III