PI: Richard Nelson

We recently published a study titled Spirals, rings, and vortices shaped by shadows in protoplanetary discs: from radiative hydrodynamical simulations to observable signatures in MNRAS (Ziampras et al 2025, MNRAS, 540, 1185). The study involved performing radiation-hydrodynamical simulations of discs in which the inner and outer regions are highly misaligned, causing the inner disc to cast a shadow on the outer disc. This is a phenomenon that appears to be quite common, as evidenced by several images of discs in scattered light taken in the near-IR that show shadows occurring in the outer regions of these discs.

Figure 1: Images showing aligned and misaligned discs

The set-up of the simulations in illustrated in Fig. 1, which shows cases where the inner and outer discs are either aligned or misaligned. The casting of shadows has a profound eOect on the dynamical evolution of protoplanetary discs because starlight from the central star provides the dominant heating eOect experienced by the disc. As gas orbiting the star moves in and out of the shadow, in experiences variations in its temperature and pressure, giving rise to features such as spirals, rings and vortices. Figure 2 shows the temperature perturbations and resulting density perturbations arising in one run. Our work shows the potential connection between the shadows observed in scattered light by instruments such as SPHERE and GPI, and the spirals, rings and vortices observed in the submm by ALMA. The study used the PLUTO code running on DiAL3.

Figure 2: Figure showing temperature and density perturbations induced by a shadow in the outer disc