EPoS Contribution

Influence of Turbulence in Dense Cores on the Formation and Evolution of Protostellar Disks Jinshi Sai ASIAA, Taipei, TW
Dense cores are known to be turbulent, yet the impact of large-scale turbulence on the formation and evolution of protostellar disks remains observationally unclear. We have investigated gas kinematics on scales of ~1000-10,000 au around protostellar systems, where the disk formation process is on-going. In two protostellar systems, velocity structures within a radius of ~1000 au are explained by infalling and rotational motions, while those on lager scales exhibit greater complexity. Our analysis using the second-order structure function suggests that the observed large-scale velocity structures can be consistent with turbulent motion across the dense cores (Fig. a). As demonstrated in theoretical studies, the observed turbulence levels in our study are sufficiently high to influence the dynamics in the formation of protostellar disks and their subsequent evolution. Within one of the dense cores hosting a young Class 0 protostar (IRAS 15398-3359), we observe three misaligned outflows with different dynamical times, all launched from the singe protostar (Fig. b). This suggests time variations in the orientation of the disk and outflow axes, likely attributed to the accretion of material with inhomogeneous angular momentum vectors from the dense core induced by turbulence. This potential influence of turbulence is also seen in a more evolve source. In our other study of a Class I protostar (L1489 IRS), we observe a warped disk structure (Fig. c), which would form if the later infalling material possesses a different angular momentum vector compared to the inner disk. The ratio of turbulent energy to gravitational energy observed in IRAS 15398 is below the median value in other protostellar dense cores, such as those in the Perseus star-forming region. This hints that such influence of core-scale turbulence on the formation and evolution of disks could be a common phenomenon.

Caption: (a) The results of the structure function analysis for the two protostellar system. The dependence of the velocity deviation on the spatial separation is well fitted with a power-law function with power-law indices of ~0.6, which are within a range of the power-law index of ~0.1–0.75 reported by observations of molecular clouds and expected by turbulence models. (b) The misaligned, multiple outflows observed in IRAS 15398. (c) The warped disk structure observed in L1489 IRS (contours) and a synthesized image of a warped disk model reproducing the observations (color).
Collaborators: H.-W. Yen, ASIAA, TW N. Ohashi, ASIAA, TW A. Maury, FR S. Maret, FR Y. Aso, KASI, KR M. N. Machida, KyushuU, JP K. Saigo, KagoshimaU, JP T. Matsumoto, HoseiU, JP et al.	Key publication Relevant topic(s): Disks Outflows Turbulence
Relevant Big Question: What is the impact of turbulence in dense cores on the formation and evolution of disks?