We present BVI multicolor images of the AU Microscopii
debris disk taken with the Advanced Camera for Surveys
coronagraph on the Hubble Space Telescope. AU Mic is a ~
12 Myr-old M dwarf at a distance of 10 pc and is a member
of the \beta Pictoris association. The optically-thin disk
is viewed edge-on and can be seen to within 0.75'' (7.5 AU)
of the star in the ACS images. The radial surface brightness
profile indicates that there is a central clearing within 12
AU of the star, in agreement with thermal emission
measurements. The clearing, along with small, localized
variations in the apparent dust concentration, suggests a
possible substellar perturber. The disk appears bowed at
outer radii, and modelling indicates that this is due to a
~3\circ tilt along the line of sight of the outer
disk from edge-on combined with foward scattering by the
dust. The inner disk is within 1\circ of edge-on. The
reflected light from the dust is bluer than the stellar
light. This may indicate that there is a relative surplus of
smaller grains compared to the grain size distributions in
other debris disks, which appear either neutral or red
compared to their stars. The surplus may be due to the lack
of radiation pressure that would expel small grains in disks
around more luminous stars.
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