The backreaction of stellar wobbling on accretion discs of massive protostars

Abstract: In recent years, it has been demonstrated that massive stars see their infant circumstellar medium shaped into a large, irradiated, gravitationally unstable accretion disc during their early formation phase. Such discs constitute the gas reservoir in which nascent high-mass stars gain substantial fraction of their mass by episodic accretion of dense gaseous circumstellar clumps. We aim to evaluate the effects of stellar motion, caused by the disc non-axisymmetric gravitational field, on the disc evolution and its spatial morphology. In particular, we analyze the disc propensity to gravitational instability and fragmentation, and also disc appearance on synthetic millimeter-band images pertinent to the alma facility. We employed three-dimensional radiation-hydrodynamical simulations of the surroundings of a young massive star in the non-inertial spherical coordinate system, adopting the highest spatial resolution to date and including the indirect star-disc gravitational potential caused by the asymmetries in the circumstellar disc. The resulting disc were postprocessed with the radiation transfer tool RADMC-3D and CASA softwear to obtain disc synthetic images. The redistribution of angular momentum in the system makes the disc smaller and rounder, reduces the number of circumstellar gaseous clumps formed via disc gravitational fragmentation, and prevents the ejection of gaseous clumps from the disc. The synthetic predictive images at millimeter wavelengths of the accretion disc including stellar wobbling are in better agreement with the observations of the surroundings of massive young stellar objects, namely, AFGL 4176 mm1, G17.64+0.16 and G353.273, than our numerical hydrodynamics simulations omitting this physical mechanism. Our work confirms that stellar wobbling is an essential ingredient to account for in numerical simulations of accretion discs of massive protostars.