\documentclass{amsart}
\usepackage{amsmath,amssymb,nopageno}
\usepackage[all]{xy}
\begin{document}
 \begin{equation*}
  \xymatrix@C+2em@R+2em{
   F(X) \ar[r]^{F(f)} \ar[d]_{\eta_X} & F(Y) \ar[d]^{\eta_Y} \\
   G(X) \ar[r]_{G(f)} & G(Y)
  }
 \end{equation*}
\end{document}