Misaligned disks induced by infall

M Kuffmeier,S Reissl,C P Dullemond,F G Goicovic

doi:10.1051/0004-6361/202039614

Abstract

Arc- and tail-like structures associated with disks around Herbig stars can be a consequence of infall events occurring after the initial collapse phase of a forming star, consistent with the observation of luminosity bursts. An encounter event of gas with an existing star can lead to the formation of a second-generation disk significantly after the initial protostellar collapse phase. Additionally, observations of shadows in disks can be well described by a configuration of a misaligned inner and outer disk, such that the inner disk casts a shadow on the outer disk. Carrying out altogether eleven 3D hydrodynamical models with the moving mesh code AREPO, we tested whether a late encounter of an existing star–disk system with a cloudlet of gas can lead to the formation of an outer disk that is misaligned with respect to the primordial inner disk. Our models demonstrate that a second-generation disk with a large misalignment with respect to an existing primordial disk can easily form if the infall angle is large. The second-generation outer disk is more eccentric, though the asymmetric infall also triggers eccentricity of the inner disk of e ≈ 0.05 to 0.1. Retrograde infall can lead to the formation of counter-rotating disks and enhanced accretion. As the angular momentum of the inner disk is reduced, the inner disk shrinks and a gap forms between the two disks. The resulting misaligned disk system can survive for ~100 kyr or longer without aligning with each other even for low primordial disk masses given an infall mass of ~10−4 M⊙. A synthetic image for one of our models reveals shadows in the outer disk similar to the ones observed in multiple transition disks that are caused by the misaligned inner disk. We conclude that late infall onto an existing star–disk system leads to the formation of a misaligned outer disk for infall that is inclined with respect to the orientation of the inner disk. Infall might therefore be responsible for observations of shadows in at least some transition disks.

Highlights

The formation of disks is a natural consequence of the star formation process, and circumstellar disks are important as they are the birthplace of planets (Keppler et al 2018; Müller et al 2018; Christiaens et al 2019; Haffert et al 2019; Pinte et al 2018, 2019, 2020; Teague et al 2018, 2019; Pérez et al 2020)
Carrying out altogether eleven 3D hydrodynamical models with the moving mesh code AREPO, we tested whether a late encounter of an existing star–disk system with a cloudlet of gas can lead to the formation of an outer disk that is misaligned with respect to the primordial inner disk
Hydrodynamical models with the moving-mesh code AREPO demonstrate that for a star with an already existing disk, infall of a gaseous cloudlet induces the formation of a second-generation disk around the inner primordial disk

Summary

Introduction

The formation of disks is a natural consequence of the star formation process, and circumstellar disks are important as they are the birthplace of planets (Keppler et al 2018; Müller et al 2018; Christiaens et al 2019; Haffert et al 2019; Pinte et al 2018, 2019, 2020; Teague et al 2018, 2019; Pérez et al 2020). Some studies show that a (sub)stellar perturber inside (Nixon et al 2013) or outside the disk (Dogan et al 2015) can warp and break the disk, misaligned systems might be induced by a perturbing object such as a giant planet or. Nealon et al (2018) as well as Zhu (2019) have demonstrated that a mildly misaligned planet located in the gap of a disk can lead to a disk breaking up and substantial misalignment in the inner disk with respect to the outer disk. Gonzalez et al (2020) and Nealon et al (2020b) show that a combination of external binary and an inner planet located in the gap between an inner and outer disk is a promising explanation for the specific case of HD 100453

Objectives

Methods

Results

Discussion

Conclusion