Understanding the formation and distribution of cm-sized dust grains in DG Tau A

Planet Earth Building-Blocks - a Legacy eMERLIN Survey is mapping 'pebbles' (cm-sized dust grains) at 5 cm wavelengths for protostars at a range of evolutionary stages and masses. The survey focuses on nearby star-forming regions to systematically study discs with a high potential for planet formation. The 40 mas resolution (5-9 AU) allows us to separate disc zones comparable to where terrestrial and gas giant planets form in our Solar System. The ability to image grain growth within a few AU of young stars is a unique eMERLIN capability, allowing the investigation of how planetary cores are made and the search for protoplanet candidates. We present observations of DG Tau A (Class I-II, low-mass) at 4-6 cm, where the disc is resolved and easily distinguished from jet emission. The extended source flux is significantly higher than predicted, suggesting a pile-up of dust grains with sizes ~1 cm. We compare the disc environments of DG Tau A and TW Hya, focussing on exploring the pebble-sized grain surface densities between 0.1 to ~16 AU from the star. We discuss the benefits of follow-up observations in near-IR wavelengths necessary to understand planet formation in these systems.