A Numerical Investigation of the Back Reaction of Dust and Gas on Accretion Disc Morphology

We aim to identify and constrain the role of dust dynamics in viscous protoplanetary discs with an embedded planet as it pertains to dust gap opening. As local tidal torques sweep gas out of the path of the planet, dust is carried along due to viscous drag, with drag coupling being determined by the properties of the dust grain species (typically size). Thus the planet sweeps gaps in the dust that has settled into the midplane of the disc. As dust is evacuated and local densities rise on the inner and outer edges of the gaps, pressure builds leading to a ‘back-reaction’ that is also felt by the gas. This has been established to lead to observable structures and have a significant effect on disc dynamics. We investigate the effects of the back-reaction on how gaps appear observationally in millimeter wavelengths, as well as probe some of the underpinning physics, at various dust-to-gas ratios. For the former we initialize a series of discs, varying dust-to-gas ratio, with different grain sizes on the centimeter scale and use synthetic observations to predict possible disc morphology. For the later we similarly vary dust-to-gas ratios, but instead of grain size, we artificially enforce a desired Stokes number on the disc.