Title   Resolving the jet-disk interaction
Pi     H. Beuther
Time   18 hrs
DRSP 2.0 - section 2.2 proposal

1. Name of program: Resolving the jet-disk interaction
   Author: Henrik Beuther et al.

2. One short paragraph with science goal(s) 

Protostellar jets and molecular outflows are believed to be driven by
magneto-centrifugal winds emanating from the inner regions of the
accretion disks. These jets are considered to be the prime mechanism
to remove excess angular momentum from the protostellar system and
hence allow the protostar to rotate only moderately far below break-up
speed.  However, there exists only scarce observational evidence of
the jet-acceleration and the momentum transport from the accretion
disk into the protostellar jet and molecular outflow. While the
jet-acceleration is already interesting in itself, the angular
momentum problem and its transport to large distances away from the
protostar is a central issue in star formation in general.

The actual magneto-centrifugal jet-acceleration processes take place
on scales of a few AU, below the capability of ALMA in its early
science phase. However, observing jet and disk rotational signatures
at slightly larger spatial scales (between 10 and 100AU) allows to
infer the central physical processes indirectly (Ray et al., PPV). The
rotation of the accretion disks can be observed on scales between 10
and a few 100AU (e.g., Simon et al. 2000), and we expect to observe
jet rotation also up to scales of 50-100AU. For example, assuming
momentum conservation, a typical jet has an Alfven surface of ~5AU,
and below the Alfven surface its velocity scales with 1/r where r is
the distance from the jet-axis.  Following Bacciotti et al. (2002), we
can expect jet-rotational velocities of approximately 19, 10 and 6
km/s at 15, 30, and 50AU from the jet-axis, respectively. For typical
low-mass disk-jet sources at distances between Taurus (140pc) and
Orion (450pc), this requires a spatial resolution of ~0.05'' and a
velocity resolution in the sub-km/s regime, both well in the range of
ALMA.

Therefore we propose to observe 3 well-known disk-jet sources in the
high-excitation line of SiO(11-10) to study the collimated jet, and in
CS(10-9) to investigate the accretion disk. The SiO(11-10) line has
previously been detected toward one of the candidate sources, and CS
should be easily detected in such kind of source as well. Studying the
kinematics of the combined jet-disk system will allow to investigate
the jet-disk-rotation, the jet acceleration as well as the momentum
transport in these systems.

3. Number of sources: 3 disk-jet sources
   
4. Coordinates:

4.1. Rough RA and DEC 

     One in Taurus, one in IC348 and one in Orion

4.2. Moving target: no

4.3. Time critical: no

4.4. Scheduling constraints: (optional)


5. Spatial scales:

5.1. Angular resolution (arcsec): 0.05'' (~3.5km baselines at 480GHz)

5.2. Range of spatial scales/FOV (arcsec): 0.05'' to 10'',
     single-fields are sufficient 

5.3. Required pointing accuracy: 1''


6. Observational setup

6.1. Single dish total power data: no

     Observing modes for single dish total power: 

     (e.g., nutator switch; frequency switch; position switch;
     on-the-fly mapping; and combinations of the above)

6.2. Stand-alone ACA: no

6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: no

6.4. Subarrays of 12m baseline-ALMA antennas: no


7. Frequencies:

7.1. Receiver band: Band 8

7.2. Lines and Frequencies (GHz): SiO(11-10) at 477.5GHz and
     CS(10-9) at 489.8GHZ 

7.3. Spectral resolution (km/s): 0.5km/s

7.4. Bandwidth or spectral coverage (km/s or GHz): 8GHz for the continuum
             and 2 times 100km/s for the spectral lines.

8. Continuum flux density:

8.1. Typical value (Jy): a few mJy to a few 10 mJy

8.2. Required continuum rms (Jy or K): 0.5mJy

8.3. Dynamic range within image: 100

8.4. Calibration requirements: absolute      ( 1-3% / 5% / 10% / n/a ) 10%
                               repeatability ( 1-3% / 5% / 10% / n/a ) 10%
                               relative      ( 1-3% / 5% / 10% / n/a ) 10%


9. Line intensity: 

9.1. Typical value (K or Jy): between a few 10 and a few 100mJy

9.2. Required rms per channel (K or Jy): ~5mJy/beam

9.3. Spectral dynamic range: 500

9.4. Calibration requirements: absolute      ( 1-3% / 5% / 10% / n/a ) 10%
                               repeatability ( 1-3% / 5% / 10% / n/a ) 10%
                               relative      ( 1-3% / 5% / 10% / n/a ) 10%


10. Polarization: no

10.1. Required Stokes parameters:

10.2. Total polarized flux density (Jy):

10.3. Required polarization rms and/or dynamic range:

10.4. Polarization fidelity:

10.5. Required calibration accuracy:


11. Integration time for each observing mode/receiver setting (hr): 6
    hours on-source, plus overhead.

12. Total integration time for program (hr): 18 hours plus overhead for
                                             calibration, pointing etc.

13. Comments on observing strategy : (optional)

    (e.g. line surveys, Target of Opportunity, Sun, ...):
--------------------------------------------------
Review v2.0:
 
2.2.12 - 2.2.15  

I found no problems with these proposals other than the standard
question of calculating ACA time.