Plumber generates full Stokes primary beam models for radio interferometers using Zernike model coefficients of the antenna aperture illumination pattern. The generated PB models are scaled and matched to the input image coordinate system in order to use standard PB correction tools (such as those found in CASA).

As of 2021 this supports VLA S Band and MeerKAT L band observations, although support for other telescopes and bands is simply a question of providing the coefficients via the input CSV file.

Table of Contents

• Installation
• Usage
• Citation

Installation

Note The spectral-cube dependency points to the master branch, pending the stable release of certain bleeding-edge features that are required by plumber.

Installation via pip

Clone the repo, then cd into the cloned directory and run

pip install .

It is advisable to run the above command within a Python virtual environment, created using your favourite tool (e.g., conda or pyenv).

Usage:

plumber <path_to_template_image> <path_to_coefficient_csv> [options]

The full command line arguments :

``` Usage: plumber [OPTIONS] IMAGENAME CSV

Given the input image and the coefficient CSV file, generate the full Stokes primary beam at the image centre frequency. If the input is a cube, a corresponding output cube of PBs will be generated, for each of the Stokes-I, -Q, -U and -V beams.

To pass in a beginning and end parallactic angle, pass in --parang twice, like

plumber --parang 20 --parang 110

The CSV file must be of the format

#stokes,freq,ind,real,imag,eta

The eta column in the CSV is optional.

Options: -a, --padding INTEGER Padding factor for aperture, affects smoothness of output beam [default: 8]

-d, --dish_dia FLOAT Diameter of the antenna dish. If not one of VLA, ALMA, MeerKAT or GMRT, must be specified.

-l, --islinear Specifies if the telescope has linear feeds. If not one of VLA, ALMA, MeerKAT or GMRT, must be specified

-I, --stokesI Only generate the Stokes I beam, not the full Stokes beams

-P, --parallel Use parallel processing (no MPI) to speed things up -p, --parang FLOAT Beginning (and optionally end) parallactic angle for the PB. Pass --parang twice to specify beg and end.

-h, --help Show this message and exit. ```

Determining parallactic angle

In order to rotate the beams to the right parallactic angle, the parang_finder helper script is bundled with plumber.

``` Usage: parang_finder [OPTIONS] MS

Helper script to determine the range of parallactic angles in an input MS.

Part of the plumber package to generate full Stokes beam models.

Options: --field TEXT Name of field to consider, must match exactly the name in the MS. If this is not specified, will use the first field with the TARGET intent. --use-astropy Use astropy convention rather than CASA convention to calculate the parallactic angle -c, --calcweights Print a list of parallactic angle and associated weights -w, --binwidth INTEGER Bin width in degrees -h, --help Show this message and exit. ```

Location of coefficients

The coefficient files are within the ./plumber/data/ directory of this repository. When the repository is cloned locally, the path of the CSV files can be passed in via command line.

Citation

If you have used plumber in your research, please cite the following paper :

Sekhar, S., Jagannathan, P., Kirk, B., Bhatnagar, S., & Taylor, R. (2022). Direction-dependent Corrections in Polarimetric Radio Imaging. III. A-to-Z Solver—Modeling the Full Jones Antenna Aperture Illumination Pattern. The Astronomical Journal, 163(2), 87.

An example BibTeX entry is below : @article{Sekhar_2022, doi = {10.3847/1538-3881/ac41c4}, url = {https://dx.doi.org/10.3847/1538-3881/ac41c4}, year = {2022}, month = {jan}, publisher = {The American Astronomical Society}, volume = {163}, number = {2}, pages = {87}, author = {Srikrishna Sekhar and Preshanth Jagannathan and Brian Kirk and Sanjay Bhatnagar and Russ Taylor}, title = {Direction-dependent Corrections in Polarimetric Radio Imaging. III. A-to-Z Solver—Modeling the Full Jones Antenna Aperture Illumination Pattern}, journal = {The Astronomical Journal}, }