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We have studied the archetypal Gigahertz Peaked Spectrum radio galaxy, PKS1934-638, using the Australian Long Baseline Array, augmented with two newtelescopes that greatly improve the angular resolution of the array. These VLBIobservations represent the first scientific results from a new antenna in NZand the first antenna of the Australian SKA Pathfinder (ASKAP). A compactdouble radio source, PKS 1934-638, has been monitored over a period of 40years, and the observation described here provides the latest datum, eightyears after the previous observation, to aid in the study of the long-termevolution of the source structure. We take advantage of these new longbaselines to probe PKS 1934-638 at the relatively low frequency of 1.4 GHz, inorder to examine the effects of optical depth on the structure of the radiosource. Optical depth effects, resulting in the observation of frequencydependent structure, may have previously been interpreted in terms of anexpansion of the source as a function of time. Expansion and frequencydependent effects are important to disentangle in order to estimate the age ofPKS 1934-638. We show that frequency dependent structure effects are likely tobe important in PKS 1934-638 and present a simple two-dimensional synchrotronsource model in which opacity effects due to synchrotron self-absorption aretaken into account. Evidence for expansion of the radio source over 40 years istherefore weak, with consequences for the estimated age of the radio source.

Evolution of the pc-scale structure of PKS 1934-638 revisited: first science with the ASKAP and New Zealand telescopes