GAPS IN THE HD 169142 PROTOPLANETARY DISK REVEALED BY POLARIMETRIC IMAGING: SIGNS OF ONGOING PLANET FORMATION?

We present H-band Very Large Telescope/NACO polarized light images of the Herbig Ae/Be star HD 169142 probing its protoplanetary disk as close as similar to 0 ''.1 to the star. Our images trace the face-on disk out to similar to 1 ''.7 (similar to 250 AU) and reveal distinct substructures for the first time: (1) the inner disk (less than or similar to 20 AU) appears to be depleted in scattering dust grains; (2) an unresolved disk rim is imaged at similar to 25 AU; (3) an annular gap extends from similar to 40 to 70 AU; (4) local brightness asymmetries are found on opposite sides of the annular gap. We discuss different explanations for the observed morphology among which ongoing planet formation is a tempting, but yet to be proven, one. Outside of similar to 85 AU the surface brightness drops off roughly proportional to r(-3.3), but describing the disk regions between 85-120 AU and 120-250 AU separately with power laws proportional to r(-2.6) and proportional to r(-3.9) provides a better fit hinting toward another discontinuity in the disk surface. The flux ratio between the disk-integrated polarized light and the central star is similar to 4.1 x 10(-3). Finally, combining our results with those from the literature, similar to 40% of the scattered light in the H band appears to be polarized. Our results emphasize that HD 169142 is an interesting system for future planet formation or disk evolution studies.