I have tried to summarize material on the ACA into a document which will eventually be material for the ALMA Project Book. It is under construction, and so incomplete.
The main question is how to translate these science examples into test models for the ACA. There are several useful examples in the literature such as the HL Tau environment (Welch et al. 2000, ApJ 540, 363) and the BIMA-SONG/OVRO/Nobeyama data on nearby galaxies, but those probably have to be translated into examples with higher dynamic range. The differences in science output between ALMA+SD and ALMA+ACA+SD should be clearly demonstrable to support the ACA science case.
IRAM simulations may be found at http://iram.fr/~alma and NRAO simulations may be found at http://www.tuc.nrao.edu/~mholdawa
Example 1: Extended protostellar envelopes --- How accurate can
ALMA images reproduce its radial profile? Can we distinguish between collapse
model X and Y (e.g. Shu-type collapse vs. other collapse model)?
Image used:
A molecular line in a protostellar envelope This
model was provided by M.Hogerheijde, based on radiative transfer calculations
in an infalling and rotating envelope. Only the inner 256 pixels have been
retained. Hogerheijde has "generated new model
images of HCO+ 1-0 and HCO+ 4-3 emission; so far only the HCO+ 4-3
image seem to have been included. FITS file of these new images can be
found on
http://talisker.as.arizona.edu/~michiel/alma/hcop_10.fits
http://talisker.as.arizona.edu/~michiel/alma/hcop_43.fits
(also mentioned in the write up). The new HCO+ 4-3 replaces the previous
one. I'll send e-mail to Frederique and Stephane at IRAM asking them
if they can do some simulations based on these images, and will talk
to Mark at NRAO/Tucson to see about the MEM-based simulations."
Simulation analysis:
M.Hogerheijde has analyzed this image. Comments on the model and on the
simulations from Michiel are available.
These have been updated 26 September; please see Michiel's
other comments.
Example 2: Multiple dense cores in a GMC at a distance
of LMC --- How accurate can an ALMA image reproduce the extended diffuse
component and the
mass function of the cores embedded therein?
Image used:
A Cluster of protostars. This
model image was provided by K.Tatematsu.
Simulation analysis:
Jack Welch will commence analysis of this image.
Example 3: Face-on disk galaxies at small to intermediate distances
--- How accurate can ALMA images reproduce the extended disk component
and the brightness of the arms and the interarm regions?
Image used:
This is an optical
image of M51 in the H line. It contains lots of small sources, with also
a low-level extended component.
Simulation analysis:
Min Yun has commenced analysis
of this image. "I would like to quantify the differences in the
ratio images better, but it is not obvious how to make it meaningful.
I'm open for suggestions.
I believe the images I analyzed are based on "typical" errors
the IRAM group considers. I should check that. These
tests clearly demonstrate the danger of not having the ACA,
but I agree with your general conclusion that M51 does not
make the critical "make-or-break" case for ACA. "
A digest of email discussions on this is available.
Example 4: Debris disk, e.g. Epsilon Eridani-type objects: How
well can ALMA image the structure in such disks?
Image used:
Lee Mundy provided a model ot this object.
Simulation analysis:
Bryan Butler and Al Wootten have commenced analysis
of this image.
Example 5: A Turbulent Cloud
Image used:
This model was
provided by J.Pety. The power spectrum of the emission is known from the
model.
Simulation analysis:
Someone may analyze this image.
Example 6:An HII region in M31
Image used:
This is an image
of a giant HII region in M31 as seen by the VLA. The image was used by
K-I.Morita in its MEM simulations using the SDE software.
Simulation analysis:
Analysis is needed, should simulations proceed on this image.
Wootten looked at these images, finding them quite different also. His comments might make some sense.
-Revised 5 September 2001 HAW