Into the thick of it: ALMA 0.45 mm observations of HL Tau at a resolution of 2 au

Vol. 686
10. Planets and planetary systems

Into the thick of it: ALMA 0.45 mm observations of HL Tau at a resolution of 2 au

The disk orbiting the pre-main-sequence star HL Tau presents a series of striking bright and dark rings that have been mapped with the ALMA telescope in an already iconic image. The origin of these rings is still under debate, but a favored interpretation is that they originate from the interaction between the disk and its nascent planets. To further characterize the dust in the HL Tau disk, Osmar Guerra-Alvarado and collaborators present new ALMA images with a higher resolution of 2 au at a wavelength of 0.45 mm. At this higher frequency, the emission from the dust is optically thick and therefore highly sensitive to the temperature structure of the dust. These new images reveal an asymmetry in the emission coming from the first ring that is interpreted as a combination of very optically thick emission, a moderately inclined disk, and a large dust scale height. The images, in addition, show an increase in brightness temperature inside the estimated water snow line. This could indicate a pileup of small particles due to a decrease in the drift velocity of the small grains after crossing the water snow line.