\documentclass{standalone}

\usepackage {tikz}
\usepackage{pgfplots}
\usetikzlibrary{pgfplots.groupplots}

\pgfmathdeclarefunction{gauss}{2}{%
  \pgfmathparse{1/(#2*sqrt(2*pi))*exp(-((x-#1)^2)/(2*#2^2))}%
}

\begin{document}
\begin{tikzpicture}
    \begin{groupplot}[
        group style={group name=gaussians, group size=1 by 3, %quantas linhas?
            xlabels at=edge bottom, xticklabels at=edge bottom, % coloca x axis so embaixo
            vertical sep=0pt}, %fica juntinho
        every axis plot post/.append style={mark=none,domain=-3:3,samples=50,smooth}, % como popular as curvas
        footnotesize, xlabel=Nome do eixo?, % tamanho fonte e nome eixo
        width=8cm, height=3cm, xmin=-3, xmax=3, ymin=0, ymax=1, % medidas do grafico
        xtick={-3, -2, ..., 3}, ytick={0}, % ticks
        tickpos=left, ytick align=outside,xtick align=outside] % configuracao das marquinha
\nextgroupplot[y coord inv trafo/.code={\pgfmathparse{\pgfmathresult + 0}}] % hack pra mudar yticks
\addplot[draw=blue] {gauss(0,0.5)};
\nextgroupplot[y coord inv trafo/.code={\pgfmathparse{\pgfmathresult + 1}}]
\addplot[draw=red] {gauss(1,0.75)};
\nextgroupplot[y coord inv trafo/.code={\pgfmathparse{\pgfmathresult + 2}}]
\addplot[draw=green] {gauss(-1, 0.4)};
\end{groupplot}
\end{tikzpicture}

\end{document}