http://arxiv.org/abs/1810.12007
Polycyclic aromatic hydrocarbon (PAHs) and nanoparticles are expected to play an important role in many astrophysical processes due to its dominant total dust surface area, including gas heating, chemistry, star formation tracer, and anomalous microwave emission. In dense magnetized molecular clouds where low-velocity shocks are present, PAHs and nanoparticles are widely believed to originate from grain shattering due to grain-grain collisions. However, the question is whether these nanoparticles can survive in the dense and hot shocked regions, and how to constrain the size and abundance of these tiny particles via observations. In this paper, we show that, due to high gas temperature and supersonic drift of neutrals relative to charged grains, smallest nanoparticles can be spun-up to extremely fast rotation by stochastic atom bombardment such that centrifugal force can disrupt non-ideal nanoparticles of size below $\sim 2$ nm. The proposed disruption mechanism is shown to be more efficient than sputtering in affecting the lower cutoff of grain size distribution in C-shocks if nanoparticles have non-ideal tensile strength. We model spinning dust emission from spinning nanoparticles subject to supersonic drift and rotational disruption. We find that suprathermally rotating nanoparticles can emit strong microwave radiation and peak frequencies increasing with the drifting velocity. We suggest a new method to trace nanoparticles and shock velocities in dense regions using microwave emission from spinning dust.
T. Hoang and L. Tram
Tue, 30 Oct 18
69/73
Comments: 18 pages, 14 figures; Submitted