astrofle / qac

Quick Array Combinations: front end to CASA to run tp2vis, feather and various array combination methods

Quick Array Combinations (QAC)

QAC provides a set of functions that mostly call CASA tools and tasks to help you combining data from a single dish and interferometer. QAC hides some of the complexity of writing CASA scripts and provide a simple interface to array combination tools and tasks in CASA.

This project was conceived alongside the TP2VIS project, where it was used to provide an easier way to call CASA, and perform regression tests. We still keep these within QAC as they are not distributed with TP2VIS. In an earlier version these functions were called QTP. We also use QAC for an ngVLA design study.

See the INSTALL file for ways how to install and use these functions in your CASA shell.

For documentation on the available QAC routines, see docs/qac.md.

Example

Below a plot in which the top left panel is a selected channel from an ALMA total power (TP) observation of the CO emissions of a small region in the SMC. Overlayed on this greyscale are the pointing centers of the 12-m Array. For one pointing the true extend of the 12 m field of view is given as well with the larger green circle. The top right panel is the reconstructed TP map from the pseudo-visibilities generated from a virtual interferometer emulating the short spacings. The pure interferometric map that combines the 7m and 12 m data is shown in the lower left panel, and combining the TP visibilities with those of the 7m+12m arrays are then shown in the lower right panel, now recovering the large scale flux, as well as the finer scale structure.

Benchmarks

A better supported show of QAC functionality is currently in the test/bench.py, bench0.py and sky1.py routines [March 2018] as those were used in the SD2018 workshop. Please note the software in that repo is not maintained anymore, and updated versions can be found within QAC.

References

• CASA reference manual and cookbook : http://casa.nrao.edu/docs/cookbook/
  • Measurement Set: https://casa.nrao.edu/casadocs/latest/reference-material/measurement-set
  • MS V2 document: MS v2 memo
• CASA simulations: https://casa.nrao.edu/casadocs/latest/simulation
  • Simulations (in 4.4) https://casaguides.nrao.edu/index.php/Simulating_Observations_in_CASA_4.4
  • See also our workflow4
• CASA single dish imaging: https://casa.nrao.edu/casadocs/latest/single-dish-imaging
  • Mangum et el. 2007: OTF imaging technique
• CASA feather: https://casa.nrao.edu/casadocs/latest/image-combination/feather
• CASA data weights and combination: https://casaguides.nrao.edu/index.php/DataWeightsAndCombination
• Nordic Tools SD2VIS: https://www.oso.nordic-alma.se/software-tools.php
• Kauffman's Adding Zero-Spacing workflow: https://sites.google.com/site/jenskauffmann/research-notes/adding-zero-spa
• Radio Imaging Combination Analysis (RICA) : https://gitlab.com/mileslucas/rica
• Papers of interest:
  • Ekers and Rots
  • Braun and Walterbos 197x?
  • Vogel et al. 1984?
  • Jorsater and van Moorsel 1995
  • Kurono, Morita, Kamazaki 2009
  • Koda et al. 2011