Jets from Protostars: Smith, Rosen, Moraghan

This page represents your gateway to our archives on virtual jets

The latest publication goes back to 2D to study the influence of jet speed and jet composition with high spatial resolution: Velocity study of axisymmetric protostellar jets with molecular cooling


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 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

tracer   H2 1-0 S(1) movie   H2 2-1 S(1) movie   CO J=2-1 movie   CO J=2-1 velocity channel
1 degree precession 1.8 Mb 1.8 Mb 1.4 Mb 1.5 Mb
5 degree precession 1.8 Mb 1.8 Mb 1.4 Mb 1.5 Mb
10 degree precession 1.5 Mb 1.6 Mb 1.2 Mb 1.9 Mb
20 degree precession 1.3 Mb 1.1 Mb 1.0 Mb 3.0 Mb
Slow precession,pulsed 0.8 Mb 0.8 Mb 1.2 Mb 1.9 Mb
Slow precession, stream 0.7 Mb 0.8 Mb 1.1 Mb 1.9 Mb

Spitzer mpegs: outflows seen at different viewing angles.....

tracer   IRAC Band 1   IRAC Band 4
10 deg. Slow precession, stream 1.8 Mb 1.8 Mb
20 deg. fast precession 1.8 Mb 1.8 Mb

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.


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 papers, Rosen and Smith investigate the physical and observational properies of jets from protostars.

Paper 1: Movies, Pictures and Summary: Evolving or outbursting molecular jets

Paper 2: Movies Highly collimated outflows. The effect of relative density

Paper 3: Movies Molecular outflows driven by fast-precessing jets

Paper 4: Molecular outflows driven by slow-precessing jets

Paper 4: Now available on astro-ph: astro-ph/0411771, and ADS. Movies are linked through the above table.

Paper x+1: Spitzer space telescope predictions

Michael D. Smith
Update: November 2006