Oral Presentation

Multi-wavelength characterization of dust particles in the HL Tau disk

Author(s): Takahiro Ueda (Center for Astrophysics, Harvard & Smithsonian), Sean Andrews (Center for Astrophysics, Harvard & Smithsonian), Carlos Carrasco-Gonzalez (Institute of Radio Astronomy and Astrophysics, National Autonomous University of Mexico), Osmar Guerra-Alvarado (Leiden Observatory), Satoshi Okuzumi (Institute of Science Tokyo), Ryo Tazaki (The University of Tokyo), Akimasa Kataoka (National Astronomical Observatory of Japan)

Presenter: Takahiro Ueda (Center for Astrophysics, Harvard & Smithsonian)

We present a comprehensive analysis of the dust disk around HL Tau by modeling its multi-wavelength intensity profiles at six wavelengths ranging from 0.45 to 7.9 mm with a resolution of 0.05 arcsec. Using a Markov Chain Monte Carlo (MCMC) approach, we try to constrain key dust properties, including temperature, surface density, maximum grain size, composition, filling factor, and size distribution. The full modeling, with all six parameters free, shows a preference for organics-rich dust with a low filling factor in the outer region, where the spectral index is 3.7. However, amorphous-carbon-rich dust can still reasonably reproduce the observed intensity profile. If the dust is moderately porous and organics-rich, both the predicted dust surface density and dust size can be sufficiently large for the pebble accretion rate to be a plausible mechanism for forming potential planets in the disk. In contrast, if the dust is amorphous-carbon-rich, forming a giant planet core via pebble accretion is unlikely due to the combined effects of a predicted low dust surface density and small dust size to explain the observed intensity. This suggests that other mechanisms, such as disk fragmentation due to gravitational instability, may be responsible for planet formation in the HL Tau disk. In this talk, we will overview these results and highlights the importance of (sub-)centimeter observations such as ALMA Band 1.