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See also MDS2


Molonglo deep sky survey of radio sources.I. Dec Zone -20d.

Robertson J.G.


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 sr. This covers (with some excluded areas) right ascensions 01h00m - 06h44m and 13h45m-17h19m, with a range in declination of 41'. Eighteen contour maps are given of sources that are extended or have very close companions. A thorouth error analysis is given, as well as new operational definitials 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" and 6" at 250 mJy.

2. Observations

A short description of the Molonglo 1.6 km telescope and references to more detailed accounts have been given by Devies et al. (1973). The telescope is a meridian transit instrument, providing a comb of 11 simultaneous pencil beams along the meridian, separated by half the beamwidth and spanning about 1/4^o of declination in all. For the present survey, the beamwidth of the individual pencil beam was 2.66' in RA and 2.97' in dec, and the usual tapered aperture distribution was used.
The observations were made in Sep. 1973 over a period of 16 days, and consist of drift scans with the telescope set to one declinatios number during the transit of the RA range of the survey, and scanning a long narrow strip of sky.

4. Calibration

The flux densities in the present catalogue are given on the scale due to Wyllie (1969MNRAS..142..229, 1969PAuSA...1..234). Hunstead (1972MNRAS..157..367) has established a grid of subcalibtators on this scale, and 16 of these were used as calibration sources for the observing session. All were over 4Jy, so noise and confision errors were neglible even for a single observation. The sources were
The flux densities were given by Hunstead (1972).


Robertson J.G.

Molonglo deep sky survey of radio sources.II. Dec Zone -62d.


Results are given for the second zone of a deep survey made at 408 MHz Wdh the Molonglo cross. The catalogue lists positions and flux densities for 95 sources, none of which has been previously catalogued, in a solid angle of 5.51 x 10^-3 sr. The right ascensions covered (with some excluded areas) are 18h26m to 00h06m, with a range in declination of 45'. The lower limit of flux density is 84 mJy. An upper limit of looo mJy has also been imposed. The position uncertainties are typically 12 at 100 mJy and 6 at 250 mJy.

1. Introduction

The first instalment of the Molonglo deep sky survey, made at -20 deg, is given in Part I (Robertson 1977a, present issue pp. 209-30), while the number-flux density counts from both instalments are given in Part III (Robertson 1977b, present issue pp. 241-9). The present paper gives the second instalment of the deep sky survey, and contains the results from declination zone -62 deg. The sensitivity of the Molonglo cross is greater at declinations well south of the equator, due to the increased time taken for each source to transit through the beams of the telescope. The improvement in sensitivity for this survey relative to that at -20 deg was, however, not as great as expected (Robertson 1976).