The radial profile of dust grain size in the protoplanetary disc of DS Tau

Abstract

ABSTRACT How do dust grains in protoplanetary discs overcome rapid radial drift and grow from micron size particles to planets is not well understood. The key is to search for evidence of dust accumulation and growth as a function of radius in the disc. We investigate the radial profile of grain size in the DS Tau disc by fitting multiband ALMA observations with self-consistent radiative transfer models. The best-fit grain sizes range from centimeters in the inner disc down to ${\sim }\, 30\, \mu {\rm m}$ in the outer regions. Such an inside-out decreasing tendency is consistent with theories of dust evolution. Based on the best-fit model, we find that dust of ${\sim }\, 2$ Jupiter masses has been depleted within the gap. By taking the gas-to-dust mass ratio into account, the lost mass is enough to form the 3.5 Jupiter mass planet inferred by literature hydrodynamic simulations. Moreover, our modelling also indicates that at the interface region between the gap and the ring, the grain size profile shows a discontinuity, with its amplitude dependent on the dust model adopted in the radiative transfer analysis. Future multiwavelength observations at higher angular resolutions are required to better constrain the grain size and its variation in the vicinity of disc substructures.