We present the data and analysis of VLBI observations at 1.6, 5 and 15 GHz of
a sample of faint Gigahertz Peaked Spectrum (GPS) sources selected from the
Westerbork Northern Sky Survey (WENSS). The 5 GHz observations involved a
global array of 16 stations and yielded data on the total sample of 47 sources.
A subsample of 26 GPS sources with peak frequencies > 5 GHz and/or peak flux
densities > 125 mJy was observed with the VLBA at 15 GHz. A second subsample of
29 sources, with peak frequencies <5 GHz, was observed at 1.6 GHz using a 14
station global VLBI array. In this way, 44 of the 47 sources (94%) in the
sample were observed above and at or below their spectral peak. Spectral
decomposition allowed us to identify 3, 11, 7, and 2 objects as compact
symmetric objects, compact doubles, core-jet and complex sources respectively.
However, many of the sources classified as compact double or core-jet sources
show only two components making their classification rather tentative. This may
explain why the strong morphological dichotomy of GPS quasars and galaxies
found for radio-bright GPS sources, is not as clear in this faint sample.Comment: Latex, 18 pages, 8 figures; MNRAS, accepted. The paper, with higher
quality figures, may also be obtained from http://www.ast.cam.ac.uk/~snellen
. Minor comments of referee incorporate