Occurrence of instability through the protostellar accretion disks by landing of low-mass condensations

Abstract

Low-mass condensations (LMCs) are observed inside the envelope of the collapsing molecular cloud cores. In this research, we investigate the effects of landing LMCs for occurrence of instability through the protostellar accretion disks. We consider some regions of the disk where duration of infalling and landing of the LMCs are shorter than the orbital period. In this way, we can consider the landing LMCs as density bumps and grooves in the azimuthal direction of an initial thin axisymmetric steady state self-gravitating protostellar accretion disk (nearly Keplerian). Using the linear effects of the bump quantities, we obtain a characteristic equation for growth/decay rate of bumps; we numerically solve it to find occurrence of instability. We also evaluate the minimum-growth-time-scale (MGTS) and the enhanced mass accretion rate. The results show that infalling and landing of the LMCs in the inner regions of the protostellar accretion disks can cause faster unstable modes and less enhanced accretion rates relative to the outer regions. Also, more fragmentation of landed LMCs in the azimuthal direction have less chance for instability, and then can produce more values of enhanced mass accretion rate.

Thermal Effects of Ambipolar Diffusion during the Gravitational Collapse of a Radiative Cooling Filament

“…The AD heating has been considered an important heating mechanism in molecular clouds by many authors (e.g., Scalo 1977;Zweibel & Josafatsson 1983;Elmegreen 1985;Padoan et al 2000;Nejad-Asghar 2011;Li et al 2012;Elyasi & Nejad-Asghar 2016). It is useful to compare the dynamical timescale with the ambipolar diffusion timescale.…”