HD 100546 is a well-studied Herbig Be star-disk system that likely hosts a close-in companion with compelling observational evidence for an embedded protoplanet at 68 AU .
We present ALMA observations of the HD 100546 disk which resolve the gas and dust structure at ( sub ) mm wavelengths .
The CO emission ( at 345.795 GHz ) originates from an extensive molecular disk ( 390 \pm 20 AU in radius ) whereas the continuum emission is more compact ( 230 \pm 20 AU in radius ) suggesting radial drift of the mm-sized grains .
The CO emission is similar in extent to scattered light images indicating well-mixed gas and \mu m-sized grains in the disk atmosphere .
Assuming azimuthal symmetry , a single-component power-law model can not reproduce the continuum visibilities .
The visibilities and images are better reproduced by a double-component model : a compact ring with a width of 21 AU centered at 26 AU and an outer ring with a width of 75 \pm 3 AU centered at 190 \pm 3 AU .
The influence of a companion and protoplanet on the dust evolution is investigated .
The companion at 10 AU facilitates the accumulation of mm-sized grains within a compact ring , \approx 20–30 AU , by \approx 10 Myr .
The injection of a protoplanet at 1 Myr hastens the ring formation ( \approx 1.2 Myr ) and also triggers the development of an outer ring ( \approx 100–200 AU ) .
These observations provide additional evidence for the presence of a close-in companion and hint at dynamical clearing by a protoplanet in the outer disk .