Open Access Repository

Compact structure in southern peaked spectrum radio sources

Downloads

Downloads per month over past year

King, EA (1994) Compact structure in southern peaked spectrum radio sources. PhD thesis, University of Tasmania.

[img]
Preview
PDF (Whole thesis)
King_whole_thes...pdf | Download (7MB)
Available under University of Tasmania Standard License.

| Preview

Abstract

Data for a sample of forty three Southern radio sources is presented. The majority
of the sources have spectra that are steep at high frequencies and that peak, or
at least flatten markedly, below a few giga-hertz. The sources have been studied
through both single dish observations and VLBI.
A dual frequency (2.3 and 8.4 GHz) flux density monitoring program lasting
nearly two and a half years and comprising measurements of all sources at intervals
of between one and three weeks has shown that the incidence of variability is
systematically low in peaked spectrum sources. This observation is consistent
with the assertion that the energy source powering the luminous cores in this
type object is of a different nature to that driving the compact cores seen in
many powerful fl.at spectrum radio sources. In order that the observations could
be performed on a regular basis with minimum user intervention, an automated
observing and data acquisition system was implemented. To stabilise the receiver
gain, the system incorporates a versatile.software implementation of a noise adding
radiometer. ·
The recently established Southern Hemisphere VLBI Experiment (SHEVE)
array is described and its capabilities and limitations discussed. The operational
procedures and special difficulties inherent in the operation of the array are explained.
Images for nine sources made from observations with the SHEVE array are
presented. For seven of the sources, images are available at both 2.3 and 8.4 GHz.
The images have a mean dynamic range of 65: 1 and provide accurate measu!ements
of the detailed structure in these sources, including component sizes, flux densities
and spectral indices. All of the peaked spectrum sources imaged are doubles and
few show any evidence of significant extended structure. These data constitute
the first high resolution observations for six of the sources.
Observations with a single baseline interferometer have provided the first survey
of the compact structure in thirty eight of the sources in the sample. Simple
models representing the basic source structures have been fit to the data for all
objects detected in this survey. These models show that about two thirds of the
sources surveyed have more than one component at milli-arcsecond resolution. A
comparison of the models with the images is used to set limits on the reliability
of the model fitting results.
A database of all the source properties obtained, both through the observations
described, and compiled from the literature is presented. Numerous parameters
intrinsic to the sources are calculated using these data and are briefly discussed.

Item Type: Thesis (PhD)
Keywords: Radio sources (Astronomy)
Copyright Holders: The Author
Copyright Information:

Copyright 1994 the author

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1994. Includes bibliographical references (p. 207-211)

Date Deposited: 19 Dec 2014 02:32
Last Modified: 07 Sep 2016 23:02
Item Statistics: View statistics for this item

Actions (login required)

Item Control Page Item Control Page
TOP