[asac]some science examples for calibration

[Christine Wilson]

Hi, everyone,

Here is a summary of the science examples for calibration that John and I 
have received so far. Thank you to Ken Tatematsu and Brenda Matthews 
(Berkeley) for their contributions.

Chris

-------------------------

Flux/bandpass calibration; beam pattern:

In order to investigate how molecular clouds form in galaxies,
one will propose to map extragalactic, early-phase molecular
clouds in the nearby galaxy, e.g., M51, in the 492 GHz CI 3P1-3P0 line,
For the single-dish sampling,
one should know contribution of the CI  emission
in the error pattern (about 30 % of the total).
In addition to the accurate knowledge of the beam pattern,
we may need to know the CI distribution
(with velocity infomation) outside of the area
of interest, to obtain well-calibrated line-strength.

Polarization

"normal"
-measure polarization morphology in an isolated protostar or 
	circumstellar disk; similar requirements apply to measuring	
	the polarization of Sgr A* in the mm/submm 
- polarization percentage 0.5-5%
- S/N 5-10 (to get 11-6 degrees uncertainty on position angle)
- continuum mode
- frequency ~300 GHz (whatever combination of dust emissivity and 
receiver sensitivity gives the best overall sensitivity is what would be 
prefered)

"demanding"
-same experiment as above but in a region with extended and complex 
	emission so that Single Dish polarization data must be included 
	with the same overall requirements

"demanding"
-use the dispersion in the polarization angle to measure the magnetic 
	field strength in the plane of the sky versus radius in an 
	extended star forming region like a massive protostar
- polarization percentage: down to 0.1% (to get low polarization in the 
	extended envelope)
- S/N = 10 (for 6 degree uncertainty in polarization angle)
- continuum mode as in previous examples

"demanding"
- measure polarization pattern at several frequency to use the spectrum 
	of polarizations to constrain dust grain properties; could also
	be interesting to measure Sgr A* polarization at several frequencies
- polarization percentage 0.5-5% (but maybe lower in some cases)
- S/N 5-10 
- continuum mode
- range of frequencies i.e. 100 GHz, 300 GHz, 800 GHz with matched
  angular resolution

"demanding" ?
- use the linearly polarized emission from CO lines to probe magnetic
field geometries in protostellar outflows.  (other lines, i.e., HCN, are
also possible).  At high resolution (10s of AU in nearby regions), these
data could test mechanisms for generation of outflows (i.e. X-winds vs.
disks, if the theorists will make testable predictions); in more distant
sources, the magnetic field geoemetries of the outflows can be determined 
using data coupled with the Goldreich-Kylafis effect to interpret the 
polarization angles. Different configurations are predicted for dipolar 
and quadrupolar outflows.
- polarization percentage expected to decrease with J transitions
- CO 3-2 typically 1-2% in single dish observations
- need S/N 5-10 to nail down position angle with uncertainty of 10 degrees
or better
- CO 2-1 also doable, and possibly 4-3 if lower transitions are strong