Python Astronomical Stacking Tool Array: PASTA

Introduction

PASTA is a software package written in the Python programming language for median stacking of astronomical sources. It includes a number of features for filtering sources, outputting stack statistics, generating Karma annotations, formatting sourcelists, and reading information from stacked Flexible Image Transport System (FITS) images. PASTA was originally written to examine polarization stack properties, and it includes a Monte Carlo modeller for obtaining true polarized intensity from the observed polarization of a stack.
PASTA is also useful as a generic stacking tool, even if polarization properties are not being examined.

The basic operation of PASTA is to read in a sourcelist containing positions of sources to be stacked, as well as one or more FITS images. PASTA then generates an output list of stacked sources and their properties, and a pair of FITS files, one containing the median pixels of the stack, and the other containing the mean pixels.

Stacking allows the reduction of noise levels in the examination of sets of images. It produces a pseudo-source consisting of the median of all the stacked sources, with reduced background noise level. For more information on the performance of stacking, see Stil et al. 2010.

Software Requirements

PASTA uses a number of libraries to be installed prior to running. Most of these packages are available in the software repositories of the main Linux distributions.

• Python 3.4+
• Numpy 1.7.0+
• Scipy 0.7.0+
• astropy 3.0.+

Using PASTA

For more details on how to build/use pasta, see the manual.

Acknowledgements

PASTA was written by BW Keller, with scientific guidance from Jeroen Stil. This work was supported by an Discovery Grant from the Natural Sciences and Engineering Research Council to Jeroen Stil.