Jets from Protostars: Rosen and Smith
If you are looking for the latest in our series... the slow precessors...its avaiable on
the ADS, MNRAS 357, 579
..... or our new paper on
,
which includes aperture-convolved images.
Star Birth is a private affair.....
The infant protostars are still deeply embedded and hidden from view not only
to our optical telescopes, but also to our prying infrared telescopes. Nevertheless, the
birth is announced by spectacular supersonic jets and violent eruptions of
molecular gas. What physics and dynamics explain these gigantic outflows? How is the gas ejected?
What is the state of the environment? Alex Rosen and I are attempting to answer
these questions. The details are below, but if you just want the movie collection...here it is.
The movies .....precession angles1, 5, 10 and 20 degrees...
see Paper 3 for full details. And now added: slow precession - see Paper 4
for details.
mpegs: heavy jets, initially molecular, sheared
Spitzer mpegs: outflows seen at different viewing angles.....
Astrophysical Jets......
are extremely important. Here are some reasons.
1. They disrupt their maternal cloud, possibly determining
how much of the surrounding core actually accretes. That is, they
contribute towards the initial mass of the stars (and so to
the entire nature of the Universe).
2. They extract angular momentum
from close to the protostar, without which our Universe might look very
different.
3. They often point back to where a star is forming, guiding us to
the hidden baby star.
4. They crash into the ambient medium, pushing and diverting
the material through a bow wave like that created by a speed boat. The shock wave
creates intense radiation in narrow lines, revealing how molecular dynamics,
turbulence and shock physics operate in environments which would cost
us millions of Republic of Congo dollars to construct on earth.
Evolution.......
Our direct motivation has been to see how a jet and outflow EVOLVE as a
protostar evolves. The fundamental theory involves the hypothesis that some quite small
fraction of the material trying to fall onto the star is, instead, ejected into twin
oppositely-directed jets which extract quite large fraction of the spin energy or
angular momentum.
Can we learn to discriminate, from the nature of a jet, if the outflow
has just begun or if it dying away? Then, can we learn about how the star itself
is being constructed: is there a smooth evolution or does the accretion proceed
in mouthfuls?
Computer simulations......
of protostellar jets are challenging. Simulations in three dimensions are essential
to capture the properties of turbulence. Simulations of molecular destruction and
reformation must be included. Cooling and heating processes are numerous and their
feedback onto the dynamics is difficult to predict. We have constructed a Zeus-type
code to the molecular hydrodynamic problem. Earlier simulations
have now been superceded by higher resolution and more detailed cooling and
chemistry. In a series of 4 papers, Rosen and Smith investigate the physical and
observational properies of jets from protostars.
Last Revised: 2009 November 6th
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