The sample chosen for this study has been drawn from the Molonglo
Reference Catalogue (MRC, Large et al., 1981). The MRC was
the result of a 408 MHz survey made from 1968 to 1978 using the
Molonglo Synthesis Telescope (MST). The parameters of this meridian
transit instrument are summarized in Table 
.
| Operating | Bandwidth | Beamwidth | Beamwidth | Effective |
| frequency |  |  | latitude
 | |
| 408 MHz | 2.5 MHz | 2'.62 |  | -35 
|
The limiting flux density ( 
) of the MST for the detection
of a point
source near the zenith was less than 
. The MRC itself had
a limiting
flux density of 
and hence thermal noise and confusion could
not have seriously affected it. The catalogue is believed
to be 99.9% complete for flux density 
.
The MRC covers 
between 
and 
declination, excluding
a 
strip near the Galactic plane. The total number of sources
is 12141, which corresponds to an average source density of
1500 
.
Of these, 7347
sources have a flux density 
.
C. R. Subrahmanya (see McCarthy et al., 1990, 1991)
defined a subset of this sample by limiting
the right ascension and declination covered:
,
or
.
This contains 558 sources.
An additional constraint was used to create the sample used in the present study. Since one of the primary aims of this project is to study the optical morphology of radio galaxies, it was necessary that the objects being imaged subtend areas that are several arcsec across so that various techniques could be reliably used. With this in mind a redshift cutoff of 0.3 was introduced. Further, sources identified with quasars and BL Lac objects were excluded. Thus the present study includes radio galaxies from the MRC that satisfy the following criteria:
or
sample.
It consists of the 83 objects given in Table .
During the two rounds of observations when time was available for the project, 30 galaxies from the sample could be observed. These are the ones we will be using in our analysis. We will often refer to these galaxies as the sample or the radio sample.
Basic information about the sample has been included in
Table .
A Kolmogrov-Smirnov test (Figure ) shows,
at a significance level 
, that the
flux selected subsample and the original complete
sample of 83 radio galaxies belong to the same
parent population.
Figure: The histograms of radio flux at 
for the complete
low-redshift sample and the sample observed for the thesis.
The two histograms are similar in nature. A quantitative comparison
is shown in Figure using a Kolmogrov-Smirnov test.
A few comparable radio selected samples exist in the literature.
These have been reviewed
by McCarthy (1993). Specifically, the 3CRR sample
(Laing et al., 1983) is a subset from the 3CR sample.
The 3CR itself was badly affected by confusion. The
3CRR sample contains sources with 
and
is believed to be 96% complete.
The other constraints are 
and
.
Allington-Smith (1982) studied a complete sample from the
Bologna catalogue (Colla et al., 1970). The selection criteria for
the complete sample were 
, 
,
and 
.
This sample consists of
59 sources and is in many ways similar to the present sample.
Besides these northern hemisphere studies, the Parkes Selected
Regions (Downes et al., 1986) form an important sample from
the southern hemisphere.
This catalogue consists of 188 sources with 
,
is a subset of the
Parkes catalogue, and overlaps with the
MRC. However, a fifth of the overlapping Parkes sources are not included
in the MRC since the latter has a more sharply defined flux
density cut-off. Also, the
2700 MHz Parkes catalogue contains many flat-spectrum sources which fall
below the MRC cut-off.
A complete optical and NIR study has not been done on any of these samples. When presenting results from this work, comparison will be frequently made with whatever results are available on the above samples. Work on the higher redshift MRC sources (e.g. McCarthy et al., 1996, Athreya et al., 1997) will also be used for comparison.
Table: The low redshift MRC 1 Jy sample
Part 1
Part 2
Part 3
