Misaligned disks induced by infall

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.

Kinematic Structures in Planet-Forming Disks

“…The possibility of successive accretions of molecular "cloudlets" has also recently been explored (Dullemond et al 2019;Kuffmeier et al 2020). They may also lead to the formation of misaligned second-generation disks that can survive for more than 100 kyr (Kuffmeier et al 2021, see also section 4.3). Other systems show very faint large scale spirals in the outer disk that are reminiscent of low density material being slowly accreted at the outer edge of these objects (e.g., Grady et al 1999;Fukagawa et al 2004;Ardila et al 2007;Huang et al 2020Huang et al , 2021.…”

“…Numerical simulations have suggested that a misaligned companion or planet could warp or even break the disk in two or multiple precessing rings (Nixon et al 2013;Facchini et al 2013;Teyssandier et al 2013;Lodato and Facchini 2013;Nealon et al 2018;Facchini et al 2018;Zhu 2019). Infall events occurring after the initial collapse can also result in misaligned outer disks (Kuffmeier et al 2021). Late type stars are also known to possess a strong magnetic dipole moment, due to their convective nature.…”

Disk Evolution Study through Imaging of Nearby Young Stars (DESTINYS): A Panchromatic View of DO Tau’s Complex Kilo-astronomical-unit Environment

“…Together, these observations indicate that many disks are perturbed by their surroundings while planet formation is ongoing. Key theorized consequences of these external perturbations include modification of the total mass budget available for planet formation, disk truncation, inducement of misalignments or instabilities, formation of disk substructures, and stellar outbursts (e.g., Clarke & Pringle 1993;Bae et al 2015;Harsono et al 2011;Manara et al 2018;Cuello et al 2019;Dullemond et al 2019;Kuffmeier et al 2020Kuffmeier et al , 2021Kuznetsova et al 2022). Thus, mapping disk environments is crucial for understanding what processes control protoplanets' formation location and timescale, mass, orbital behavior, and survival.…”

Cloudlet Capture Model for Asymmetric Molecular Emission Lines Observed in TMC-1A with ALMA

“…Based on the above recognition, Dullemond et al (2019) have proposed that the gas accretion is sporadic in the late stage of star formation and some Class II objects have secondary disks formed by the capture of a cloudlet (see also Küffimeier et al 2019). More recently, Küffmeier et al (2021) have made numerical simulations in which the captured cloud forms an outer disk surrounding a pre-existing inner disk.…”