CO snowline shaped by dust scattering in protoplanetary disks

Sacha Gavino, Julia Kobus, Anne Dutrey, Stephane Guilloteau, Sebastian Wolf, Jes Kristian Jorgensen, Rajeeb Sharma

Characterizing the dust thermal structure in protoplanetary disks is a fundamental task as the dust temperature can affect both the disk chemical evolution and planet formation. It is a challenging task, however, since the temperature is strongly dependent on many parameters, including the grain size. Many disk chemical models employ a single dust structure designed to reproduce the effect of a realistic population composed of a large diversity of optical properties and sizes. While this represents a good approximation in most cases, it dilutes the effects of the complex radiative interactions between different grain populations on the resulting temperature structure.
We present results from detailed radiative transfer and chemistry simulations where we test the effect of the radiative interactions between multiple dust populations in a disk model. We find that the interaction of the dust scattered light between at least two dust grain populations can produce a complex temperature structure. In particular, the scattered light from the upper layers of the disk is sufficient to significantly raise the temperature of micron-sized grains in the midplane. This results in the splitting of the CO snowline that reshuffles the distribution of both CO in the gas-phase and on the grain surface. The results are compared to resolved observations of edge-on protoplanetary disks.