$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
8.60
\begin{equation} \begin{gathered}\label{equation:slice-cocompletion} \xymatrix@R =50pt@C=50pt{ \widetilde{\operatorname{\mathcal{C}}} \ar [r]^-{\widetilde{h}} \ar [d] & \widehat{\operatorname{\mathcal{C}}}_{ / f } \ar [d] \\ \operatorname{\mathcal{C}}\ar [r]^-{h} & \widehat{\operatorname{\mathcal{C}}} } \end{gathered} \end{equation}