Dust rotational dynamics in CJ-shock: rotational disruption of nanoparticles by stochastic mechanical torques and spinning dust emission. (arXiv:1902.01921v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Le_T/0/1/0/all/0/1">Tram Ngoc Le</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hoang_T/0/1/0/all/0/1">Thiem Hoang</a>
In a previous work, we studied rotational dynamics of nanoparticles in
stationary C-shocks and identified a new destruction mechanism for
suprathermally rotating nanoparticles due to centrifugal force so-called
rotational disruption. In this paper, we extend our study for non-stationary
shocks driven by outflows and young supernovae remnants that have dynamical
ages shorter than the time required for a C-shock to reach the steady state,
which is composed of a C-shock and a J-shock tail (referred as non-stationary
CJ-shocks). We find that, in the both C-shock and J-shock components, smallest
nanoparticles (size less than 1 nm) of weak materials can be rotationally
disrupted by centrifugal force due to extremely fast rotation. We then model
spinning dust emission from spinning nanoparticles by accounting for rotational
disruption in this non-stationary CJ-shock. We find that spinning nanoparticles
can emit strong microwave radiation and suggest a new method to trace
nanoparticles and shock velocities in dense molecular outflows using microwave
emission from spinning dust. Finally, we discuss two new ways that can return
molecules from the nanoparticle surface to the gas in the shocks, including
thermal evaporation and rotational desorption. The first process relies on the
fact that nanoparticles of low heat capacity can be heated to high
temperatures, which is sufficient to evaporate icy species to the gas phase.
The second process, rotational desorption, applied to strong nanoparticles of
high tensile strength that can withstand rotational disruption, occurs when the
centrifugal force acting on molecules exceeds its binding force to the grain
surface. These two new mechanisms may play an important role in chemistry in
shocks because of dominant surface area of nanoparticles.
In a previous work, we studied rotational dynamics of nanoparticles in
stationary C-shocks and identified a new destruction mechanism for
suprathermally rotating nanoparticles due to centrifugal force so-called
rotational disruption. In this paper, we extend our study for non-stationary
shocks driven by outflows and young supernovae remnants that have dynamical
ages shorter than the time required for a C-shock to reach the steady state,
which is composed of a C-shock and a J-shock tail (referred as non-stationary
CJ-shocks). We find that, in the both C-shock and J-shock components, smallest
nanoparticles (size less than 1 nm) of weak materials can be rotationally
disrupted by centrifugal force due to extremely fast rotation. We then model
spinning dust emission from spinning nanoparticles by accounting for rotational
disruption in this non-stationary CJ-shock. We find that spinning nanoparticles
can emit strong microwave radiation and suggest a new method to trace
nanoparticles and shock velocities in dense molecular outflows using microwave
emission from spinning dust. Finally, we discuss two new ways that can return
molecules from the nanoparticle surface to the gas in the shocks, including
thermal evaporation and rotational desorption. The first process relies on the
fact that nanoparticles of low heat capacity can be heated to high
temperatures, which is sufficient to evaporate icy species to the gas phase.
The second process, rotational desorption, applied to strong nanoparticles of
high tensile strength that can withstand rotational disruption, occurs when the
centrifugal force acting on molecules exceeds its binding force to the grain
surface. These two new mechanisms may play an important role in chemistry in
shocks because of dominant surface area of nanoparticles.
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