Wide-bandwidth Imaging

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COBRaS observations will utilise the 2 GHz wide bandwidths available to e-MERLIN when in full operation. When imaging COBRaS data, consideration must be made for the change in radio source brightness and primary beam pattern as a function of frequency. As e-MERLIN will be one of the first telescopes to implement such wide-bandwidths, new techniques are required.

The information below details the research into adapting current imaging software to incorporate wide-bandwidth techniques. In particular, this work makes use of the Sault-Wieringa algorithm (as described in Sault & Wieringa, AAS 108, 585-594, 1994) and python modules developed by Dr. Ian Stewart.

Image showing a radio supernova remnant (40.68+55.1) in the nearby starburst galaxy M82.
Image showing a radio supernova remnant (40.68 55.1) in the nearby starburst galaxy M82. This image was produced using MERLIN observations at three frequencies between 4.5 and 6 GHz and was processed with the IF_imager software.

The are two imaging scripts presented below, which are designed to perform wide-field imaging of wide-band data using spectral imaging techniques. All of these scripts utilise the python-based Sault-Wieringa imaging code written by I. Stewart. Theses scripts are designed to work with data and images directly situated in the AIPS environment. They perform the relevant imaging via parseltongue and write the output images directly into the AIPS catalogue.

  • IF_imager_minor.py - this utilises a single dirty image from all of the data and dirty beams from each of the IFs in the data. This performs a purely image-based clean.
  • IF_imager_major.py - this utilises a single dirty image from all of the data and dirty beams from each of the IFs in the data. This performs a data-based clean. The clean components are subtracted from the data itself and the dirty image and beams are recreated at each major cycle.
  • IF_imager.inp - the text file containg the inputs required to run the imaging software

PLEASE NOTE: this software is currently being updated. Contact D. Fenech for any problems.