The accuracy of the positions for all sources in our catalogues is limited by the
pointing accuracy and beam size of the Parkes telescope. We have compared the
positions of 20 radio sources from the MC4 catalogue (Clarke et al.
1976) with positions from our 8.55-GHz catalogue (Table 6) and have
found no significant positional bias between our radio and MC4 catalogue
positions [
, 
(8.55 GHz - MC4)].
We have also compared our 4.85-GHz catalogue positions (Table 5) with the
published PMN survey source positions (Wright et al. 1994) for
146 common objects. Again, the positional difference is satisfactory
[
(4.85 GHz - PMN)]
with standard deviations in the differences of 28
and 21
, respectively.
An additional comparison between accurate radio positions (
) for
three widely separated sources, B0020-747, B0045-757 and B0100-760, in both
White et al. (1991) and our catalogues, also shows no significant
positional bias.
The accuracy of source positions depends on the observing frequency and the source
extension. For example, by comparing the positions of sources at the different radio
frequencies, we conclude that the errors in position have a standard deviation
of 
in both right ascension and declination at 8.55 GHz.
Positional accuracies of individual sources at each frequency are presented in
Table 9 (click here) and are similar to those for the LMC (Paper IV). For each source, these
were determined by comparing the 8.55-GHz position with the position determined
at the other frequencies. These positional accuracies represent 
of the Parkes telescope beam size.
Table 9: Positional and flux density uncertainties for the SMC surveys.
Uncertainties in flux density (
)
To establish the relative flux density scales of our catalogues at 1.42, 2.45, 4.75 and 8.55 GHz we have compared our flux density with those from the PKSCAT-90 catalogue (Otrupcek & Wright 1991) which includes sources from surveys at 1.40 GHz (Mathewson & Healey 1964; McGee et al. 1976), 2.70 GHz (McGee et al. 1976; Bolton & Butler 1975; Broten 1972), 5.00 GHz and 8.80 GHz (McGee et al. 1976).
Figure 1: Comparisons of flux densities in Tables 2-6 with flux densities from
the PKSCAT-90 source compilation and that of McGee et al. (1976) at
similar frequencies. a) gives flux densities from Table 2 (measured at
1.42 GHz) compared with the 1.40-GHz flux estimates from PKSCAT-90 and
McGee et al. (1976). Similarly, b), c), d) compare flux
densities in Tables 3 (2.45 GHz), 4 (4.75 GHz) and 6 (8.55 GHz) with PKSCAT-90
fluxes at 2.70, 5.00 and 8.80 GHz, respectively. Details of the comparisons are
given in Sect. 5.2.1
Few sources in the SMC are contained in the PKSCAT-90 catalogue at 1.40 GHz. Flux densities at this frequency have been estimated (McGee et al. 1976) for a few strong sources from the 21-cm contour map of Mathewson & Healey (1964). Figure 1 (click here)a shows a comparison of source flux densities at 1.42 GHz from our survey with the estimated 1.40-GHz flux densities from PKSCAT-90 and McGee et al. (1976). The median of the ratio between our estimates and PKSCAT-90 is 1.01 (our flux densities are higher) with a standard deviation of 0.30.
Figure 1 (click here)b presents a comparison of the integrated flux density from our survey at 2.45 GHz versus the flux density at 2.70 GHz (McGee et al. 1976; Bolton & Butler 1975; Broten 1972) for 18 sources in common (excluding four very extended sources). The resulting median is 1.14 with a standard deviation of 0.16.
Figure 1 (click here)c shows a comparison of the integrated flux density of sources at 4.75 GHz versus flux density at 5.00 GHz from McGee et al. (1976). From our new survey at 4.75 GHz, we found 15 of the 27 sources. A comparison of 15 of these sources observed by McGee et al. (1976) and by us shows reasonably good agreement between the flux densities. The median ratio is 0.95 with a standard deviation of 0.40.
The comparison of flux density at 8.55 GHz versus flux density at 8.80 GHz (McGee et al. 1976) given in Fig. 1 (click here)d, shows a median ratio of 1.04 with a standard deviation of 0.41. Only nine sources are in common.
From all of these comparisons, shown in Figs. 1a to 1d, only a very few sources have spectra that do not conform to a power-law relationship. Such sources are often extended and blended with other surrounding sources or are variable. In summary, the flux densities of our catalogues (Tables 2 to 6) agree well with those of the catalogues used for comparison.
In Fig. 2 (click here)a we compare our fitted flux densities at 4.85 GHz (Table 5) with flux densities as published in the PMN source catalogue (Wright et al. 1994) at 4.85 GHz for 148 sources in common. The flux densities agree very well (ratio=1.04, SD=0.33) except for a very few clearly extended sources where the source-fitting algorithm used for the PMN catalogue is not optimized. This problem has been addressed in Paper IV and in Wright et al. (1994).
Source flux densities determined from the PMN FITS images, using the NOD2 package,
also agree well with the fitted flux densities from the 4.75-GHz survey (Fig. 2 (click here)b),
indicating an excellent consistency. The ratio (
)
is 0.99 with a standard deviation of 0.25.
Figure 2: a) compares 4.85-GHz flux densities (from Table 5) with published
flux densities determined by Wright et al. (1994) from the 4.85-GHz
Parkes-MIT-NRAO (PMN) survey. b) compares the 4.85-GHz (Table 5) with
the 4.75-GHz flux densities (Table 4). Details of these comparisons are given
in Sect. 5.2.2
Following Paper IV, we have compared the flux densities at our five frequencies
with interpolated flux densities at the same frequencies from PKSCAT-90
(Otrupcek & Wright 1991). This type of analysis gives the uncertainty in
flux density in the form:
where A and B are constants. The flux-density-independent component of uncertainty
(A) has been computed from the rms differences for weak sources (where
flux-density-dependent uncertainties are negligible) and the flux-density-dependent
uncertainties (B) have been computed from the rms differences for strong sources.
Assuming an equal rms noise for both our surveys and the PKSCAT-90 compilation,
we obtain the uncertainties listed in Table 9 (click here) which are similar to those for the LMC
(Paper IV).
For all but the very weakest sources, the uncertainty in flux density is dominated by
the flux-density-dependent component which is 
.