ALMA's dirty beams
Goal
- Produce a set of point spread function images, both snapshots and 4 hour integrations, for each of ALMA's 12m configurations, for various declinations.
- Extract interesting parameters from those images and put them in tables.
Method
ALMA will have 28 configurations (counting only the outbound ones) in its array of 12m antennas, so obviously some sort of script(s) for setting things up, running almasimmos, and summarizing the results is in order. Fortunately
CASA comes with python.
Dirty beams do not depend on the sky, but I went ahead and gave
almasimmos
a 1 Jy CLEAN component to look at:
- dec = -23
- direcshun = "J2000 18h00m00.03s %sd0m0.0s" % dec
- cl.addcomponent(dir=direcshun,flux=1.0, freq='672.0GHz')
- compname = "star672GHz_dec%s.cl" % dec
- cl.rename(compname)
- cl.done()
Generating the visibilities
testconfigs.py ran
almasimmos
with two nested loops:
- Configuration: the notable thing here is that it adjusted the pixel size for each configuration using avgsep.
- Observation length: Both snapshot (30 seconds) and extended (4 hours).
I ended up moving each declination into its own directory to maintain some sanity. CASA is able to cd without any trouble!
Summarizing the results
Provides functions for generating dirty beams with other weightings, writing the dirty beam images to FITS files, and summarizing their FWHMs, minima, and RMSs.
Example output
|
Snapshot |
4h Exposure |
Cfg. |
Min |
RMS |
Maj (mas) |
Min (mas) |
Min |
RMS |
Maj (mas) |
Min (mas) |
... |
O-03 |
-0.024 |
0.0002 |
493.351 |
425.440 |
-0.020 |
0.0001 |
512.248 |
426.609 |
O-04 |
-0.028 |
0.0007 |
432.399 |
370.056 |
-0.019 |
0.0002 |
447.253 |
370.983 |
O-05 |
-0.026 |
0.0017 |
369.905 |
317.162 |
-0.019 |
0.0006 |
383.540 |
317.847 |
... |
--
RobReid - 21 Sep 2007