The embedded giant protoplanets in HD 100546

Among all the detection of exoplanets, the esistence of giant planets on wide orbits (r > 100 au) is of major importance to test the planet formation mechanism. At such distance from the star, grain growth is inhibited primarily by the low dust density. Gravitational instability might be at work in (some) disks. And yet, according to the measurements of the total gas mass, disks do not appear to be gravitationally unstables. The occurence of such 'cold Jupiters' remains a puzzle. Interestingly, the recent ALMA high angular resolution campaigns do show the presence of dust gaps and rings in protoplanetary disks on wide orbits, on spatial scales similar to those of cold Jupiters. In this regard, HD 100546 is a remarkable system.  

The protoplanetary system HD 100546: HD 100546 is a 2.5 solar mass star surrounded by a large disk extending out to nearly 500 au. The disk show spiral arms at different spatial scales, an inner dust cavity of nearly 28 au radius, a wide dust gap between nearly 50 and 150 au and a faint and eccentric outer ring centered at 200 au. Figure 1 shows the distribution of the millimeter continuum as seen by ALMA. The peculiar disk structures can be explained with the presence of two giant protoplanets (orbiting at at nearly 15 au and 100 au) interacting with the surrounding gas and dust. Notably, HD 100546 is one of the only disk in which cold water emission has been detected. I will present some recent ALMA results along with hydrodynamical simulations and a new analysis of the water distribution in the disk.