The recent ALMA observations of the disk surrounding HL Tau reveal a very complex dust spatial distribution. We present a radiative transfer model accounting for the observed gaps and bright rings as well as radial changes of the emissivity index. We find that the dust density is depleted by at least a factor of 10 in the main gaps compared to the surrounding rings. Ring masses range from 10-100 M ⊕ in dust, and we find that each of the deepest gaps is consistent with the removal of up to 40 M ⊕ of dust. If this material has accumulated into rocky bodies, these would be close to the point of runaway gas accretion. Our model indicates that the outermost ring is depleted in millimeter grains compared to the central rings. This suggests faster grain growth in the central regions and/or radial migration of the larger grains. The morphology of the gaps observed by ALMA -well separated and showing a high degree of contrast with the bright rings over all azimuths -indicates that the millimeter dust disk is geometrically thin (scale height ≈ 1 AU at 100 AU) and that a large amount of settling of large grains has already occurred. Assuming a standard dust settling model, we find that the observations are consistent with a turbulent viscosity coefficient of a few 10 −4 . We estimate the gas/dust ratio in this thin layer to be of the order of 5 if the initial ratio is 100. The HCO + and CO emission is consistent with gas in Keplerian motion around a 1.7 M star at radii from ≤ 10 − 120 AU.

Instrumental setup and data reduction ALMA setup. ALMA Band 7 observations of HD142527 were carried out in the night of June 2 2012. The precipitable water vapor in the atmosphere was stable between 1.4 and 1.8 mm, with clear sky conditions. The ALMA correlator was configured in the Frequency Division Mode (FDM) to provide 468.750 MHz bandwidth in four different spectral windows at 122.07 kHz resolution (0.1 km/s) per channel. Each spectral window was positioned in order to target the CO(3-2) transition at 345.7959 GHz, HCO+ as well as CS(7-6) and HCN(4-3). The measured system temperatures ranged from 207 to 285 K in the different spectral windows. The number of 12 m antennas available at the time of the observation was 19, although two antennas reported very large system temperatures (DA41 and DV12) and were flagged during data reduction. Excluding calibration overheads, a total time on source of 52 minutes was spent yielding an RMS of 15 mJy in 0.1 km s −1 channels. The primary flux calibrator was Titan, which provided a mean transferred flux of 14.2 Jy for 3c279, the bandpass calibrator, and 0.55 Jy for J1604-446, the phase calibrator. Amplitude calibration used the CASA Butler-JPL-Horizons 2010 model for Titan, which gives an estimated systematic flux uncertainty of ⇠10%. All the line data were processed with continuum subtraction in the visibility domain. Image synthesis. Image synthesis was performed using two different techniques, depending on the application. For a traditional way to present the visibility dataset we use Cotton-Schwab CLEAN in the CASA package. This technique represents the consensus in image synthesis. We use Briggs weighting with robustness parameter of zero. For deconvolved models we use a non-parametric least-squares modeling technique 31 with a regularizing entropy term (i.e. as in the family of maximum entropy methods, MEM here and elsewhere). MEM model images are restored by convolving with the clean beam and by adding the residuals calculated using the difmap package 32. For the residuals we use weights comparable to our choice in CASA, a mixture of natural and uniform weights. A detailed example of this MEM algorithm is shown in the HCO + channel maps, Fig. S4. 1 Registration of ALMA images. A ⇠0.1 arcsec astrometric uncertainty could affect the ALMA data. However, we checked the astrometry by confirming that the centroid of the Keplerian velocity field (seen in the RGB image for CO(3-2) in Fig. 1) lies indeed at the po

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations from the 2014 Long Baseline Campaign in dust continuum and spectral line emission from the HL Tau region. The continuum images at wavelengths of 2.9, 1.3, and 0.87 mm have unprecedented angular resolutions of 0″. 075 (10 AU) to 0″. 025 (3.5 AU), revealing an astonishing level of detail in the circumstellar disk surrounding the young solar analog HL Tau, with a pattern of bright and dark rings observed at all wavelengths. By fitting ellipses to the most distinct rings, we measure precise values for the disk inclination (46 .72 0 .05 ± • •) and position angle (138 .02 0 .07).