Higher scale heights of millimeter grains in the embedded disk stage? The Band 9 view of HL Tau

Osmar M. Guerra Alvarado, Enrique Macias, Carlos Carrasco Gonzalez, Nienke van der Marel

In order to understand the efficiency of dust evolution in protoplanetary disks, studying disk in multiple wavelengths at high resolution with ALMA is fundamental. In this work we present ALMA observations with the highest angular resolution ever achieved on the HL Tau disk in Band 9, at a resolution of 13 mas. This high resolution image resolved for the first time the inner gap in the HL Tau system at ~13 AU, allowing us to confirm the presence of substructure in the inner parts of the disk, possibly related to the presence of the H2O snow line. Moreover, a high sensitivity image was used to improve the previously published multi-wavelength analysis in this disk. This gave us more accurate and detailed information on the dust physical properties like the temperature, density and maximum particle size. Finally, an asymmetry was observed in the NE part of the disk at this wavelength. We argue that this asymmetry is the result of the combination from optically thick emission, orientation of the disk and a high scale height. To test this, we ran several simple radiative transfer models using RADMC-3D in which a disk with a dust mass of 3 MJup and a scale height of 0.1 H/R was found to better reproduce our observations and in particular, the observed asymmetry of the HL Tau disk.