The Molonglo Deep Sky Survey of Radio Sources. I. Declination Zone -20°

Abstract

Results of a deep survey made at 408 MHz with the Molonglo cross are given. The catalogue lists positions and flux densities for a total of 373 radio sources, most of which have not previously been catalogued, in a solid angle of 0·0201 Sf. This covers (with some excluded areas) right ascensions 0l h oom-06 h 44m and 13 h 45 m -17 h 19 m , with a range in declination of 41'. Eighteen contour maps are given of sources that are extended or have very close companions. A thorough error analysis is given, as well as new operational definitions of completeness and reliability. The lower limit of flux density is 88 mJy, which is five times the r.m.s. error. An upper limit of 1000 mJy has also been imposed. Typical errors in positions are 15" at 100 mJy and 6" at 250 mJy.

A Confusion Limited Radio Survey from the Molonglo Cross

“…Confusion for the MDS2 is therefore [(11.5) 2 -(6.11) 2 ]2 = 9.7±0.4mJy. This estimate is in excellent agreement with 10.9± 1.3 mJy found by Robertson (1977a) from the MDS1. As noted by Robertson (1977a), the confusion in Molonglo data is probably equally proportioned between contributions due to weak sources and sidelobes.…”

“…This estimate is in excellent agreement with 10.9± 1.3 mJy found by Robertson (1977a) from the MDS1. As noted by Robertson (1977a), the confusion in Molonglo data is probably equally proportioned between contributions due to weak sources and sidelobes. As the confusion estimate for the MDS2 is about twice the noise estimate, the survey is effectively confusion limited and the addition of further Molonglo observations would achieve very little in terms of signal-to-noise.…”

“…The weakest source listed is 60 mjy at which level the survey is limited by confusion. Completeness is estimated to be ~-907o using Robertson's (1977a) definition.…”

“…The first Molonglo deep survey, hereafter referred to as the MDS1, resulted from observations made in 1973. The limiting flux density of the 6 = -20° and 6 = -62° sections of the MDS1 are 88 mJy and 84 mJy respectively and at these levels the survey is -90% complete (Robertson 1977a). * The weaker sources have rms uncertainties of -16 arcsec in position and ~18 mJy in flux density (~207o).…”

The Sensitivity of the V/VmTest to Uncertainties in Observed Parameters

“…This paper draws attention to the sensitivity of the VI V m statistic to various parameters and illustrates these using a complete sample of QSOs from the first Molonglo deep survey (MDS1, Robertson 1977). Spectral data is reported in White, Murdoch and Hunstead (1980) and White (1983).…”