HUBBLE SPACE TELESCOPE ACS MULTIBAND CORONAGRAPHIC IMAGING OF THE DEBRIS DISK AROUND PICTORIS1

We present F435W (B), F606W (broad V), and F814W (broad I) coronagraphic images of the debris disk around Pictoris obtained with the Hubble Space Telescope’s Advanced Camera for Surveys. These images provide the most photometrically accurate andmorphologically detailed views of the disk between 30 and 300 AU from the star ever recorded in scattered light. We confirm that the previously reported warp in the inner disk is a distinct secondary disk inclined by 5 from the main disk. The projected spine of the secondary disk coincides with the isophotal inflections, or ‘‘butterfly asymmetry,’ ’ previously seen at large distances from the star. We also confirm that the opposing extensions of the main disk have different position angles, but we find that this ‘‘wing-tilt asymmetry’ ’ is centered on the star rather than offset from it, as previously reported. The main disk’s northeast extension is linear from 80 to 250 AU, but the southwest extension is distinctly bowed with an amplitude of1 AU over the same region. Both extensions of the secondary disk appear linear, but not collinear, from 80 to 150 AU. Within 120 AU of the star, the main disk is 50 % thinner than previously reported. The surface brightness profiles along the spine of the main disk are fitted with four distinct radial power laws between 40 and 250 AU, while those of the secondary disk between 80 and 150 AU are fitted with single power laws. These discrepan-cies suggest that the two disks have different grain compositions or size distributions. The F606W/F435W an