ax1.axhline(y=0.002, xmin=0, xmax=3, c='blue', linewidth=0.5, zorder=0)
ax2.axhline(y=0.002, xmin=0, xmax=3, c='blue', linewidth=0.5, zorder=0)
ax3.axhline(y=0.002, xmin=0, xmax=3, c='blue', linewidth=0.5, zorder=0)
Plotting a horizontal line on multiple subplots in python using pyplot