Data reduction techniques for very long baseline interferometric spectropolarimetry

Kemball, Athol James (1993) Data reduction techniques for very long baseline interferometric spectropolarimetry. PhD thesis, Rhodes University.

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Abstract

This thesis reports the results of an investigation into techniques for the calibration and imaging of spectral line polarization observations in Very Long Baseline Interferometry (VLBI). A review is given of the instrumental and propagation effects which need to be removed in the course of calibrating such obervations, with particular reference to their polarization dependence. The removal of amplitude and phase errors and the determination of the instrumental feed response is described. The polarization imaging of such data is discussed with particular reference to the case of poorly sampled cross-polarization data. The software implementation of the algorithms within the Astronomical Image Processing System (AlPS) is discussed and the specific case of spectral line polarization reduction for data observed using the MK3 VLBI system is considered in detail. VLBI observations at two separate epochs of the 1612 MHz OH masers towards the source IRC+ 10420 are reduced as part of this work. Spectral line polarization maps of the source structure are presented, including a discussion of source morphology and variability. The source is sigmficantly circularly polarized at VLBI resolution, but does not display appreciable linear polarization. A proper motion study of the circumstellar envelope is presented, which supports an ellipsoidal kinematic model with anisotropic radial outflow. Kinematic modelling of the measured proper motions suggests a distance to the source of ~ 3 kpc. The cirumstellar magnetic field strength in the masing regions is determined as 1-3 mG, assuming Zeeman splitting as the polarization mechanism.

Item Type:Thesis (PhD)
Uncontrolled Keywords:Calibration, Imaging, Spectral line polarization observations, Very Long Baseline Interferometry, VLBI, Removal, Amplitude errors, Phase errors, Instrumental feed response, Polarization dependence, Astronomical Image Processing System, AIPS, Algorithms, Masers, Maps, Motion study, Circumstellar envelope, Kinetic modelling
Subjects:Q Science > QC Physics
Divisions:Faculty > Faculty of Science > Physics & Electronics
ID Code:3731
Deposited By: Philip Clarke
Deposited On:22 Oct 2012 13:51
Last Modified:22 Oct 2012 13:51
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