CASA for ALMA and other data

Once ALMA is fully operational, data cubes or other fully-calibrated products will be available as outlined under ESO ALMA Regional Centre Data Product support. Astronomers should be able to use a variety of software packages for analysis or late-stage reprocessing (e.g. to change the resolution). CASA will be particularly suitable, as it contains tasks designed to handle ALMA data. It is easy to install locally or on a laptop and is supported by copious documentation, recipes and example scripts, see Using CASA. We will help develop scripts in response to the needs of the the UK ALMA community and other users of the expertise of the UK ARC node.

CASA will also be convenient for data publishing and we are hoping to provide a facility in Manchester for users to upload their data and run basic scripts remotely.

The primary goal of CASA is to meet the needs for ALMA and EVLA data reduction but it is suitable for a wide range of radio data and is also used to compare any suitable processed data e.g. calibrated optical images.  CASA handles data internally as Measurement Sets but it can import and export FITS, as well as injesting the  Science Data Model format produced by ALMA and other modern interferometers.  Current CASA uses include:

• Full processing of VLA and EVLA spectral line and continuum data, from injesting archive format to image analysis;
• Processing SMA and other mm-wave spectral line data including mosaicing;
• Imaging MERLIN and VLBI data;
• Processing single dish data.

The best way to ensure that CASA is ready, and user-friendly, for ALMA, is to promote its early use by astronomers.  This means that we will provide support for the use of CASA to solve suitable problems in current interferometer data.  The Python interface means that, for example, if classic AIPS was required for the early stages of data reduction, you could use the Parseltongue AIPS wrapper initially and then transfer data to CASA for mosaicing images. Moreover, Python is very convenient for performing mathematical operations or running your own programs (such as plotting routines) outside CASA but integrated into a workflow.

We welcome interest from astronomers new to the radio/sub-mm regime who want to gain experience with CASA, whether by learning from tutorials using standard data sets, or whether you want to investigate importing your data into CASA to assess the possibility of future comparisons with ALMA data.

Tips and tricks

Importing ATCA spectral line data into CASA

 Extract u,v and w points from a CASA measurement set