Rings and gaps in the disc around Elias 24 revealed by ALMA

Abstract

We present Atacama Large Millimeter/sub-millimeter Array (ALMA) Cycle 2 observations of the 1.3-mm dust continuum emission of the protoplanetary disc surrounding the T Tauri star Elias 24 with an angular resolution of similar to 0.2 arcsec (similar to 28 au). The dust continuum emission map reveals a dark ring at a radial distance of 0.47 arcsec (similar to 65 au) from the central star, surrounded by a bright ring at 0.58 arcsec (similar to 81 au). In the outer disc, the radial intensity profile shows two inflection points at 0.71 and 0.87 arcsec (similar to 99 and 121 au, respectively). We perform global three-dimensional smoothed particle hydrodynamic gas/dust simulations of discs hosting a migrating and accreting planet. Combining the dust density maps of small and large grains with three-dimensional radiative transfer calculations, we produce synthetic ALMA observations of a variety of disc models in order to reproduce the gap-and ring-like features observed in Elias 24. We find that the dust emission across the disc is consistent with the presence of an embedded planet with a mass of similar to 0.7 M-J at an orbital radius of similar to 60 au. Our model suggests that the two inflection points in the radial intensity profile are due to the inward radial motion of large dust grains from the outer disc. The surface brightness map of our disc model provides a reasonable match to the gap-and ring-like structures observed in Elias 24, with an average discrepancy of similar to 5 per cent of the observed fluxes around the gap region.