Observations

The MOST is a synthesis radio telescope comprising two colinear, cylindrical-paraboloid reflectors each 11.6 m wide and 778 m long (Mills 1981; Robertson 1991). It operates at 843 MHz (a wavelength of 0.356 m) and measures right circular polarization. At the declination of the SMC a typical 12 hour observation images a field of  arcmin (right ascension by declination) with a full width half maximum (FWHM) beamwidth of  arcsec and reaches a rms noise level of 1 - 2 mJy per beam area (the beam area is  sr). Additional observations with better sensitivity were also made of several smaller fields of  arcmin containing interesting H II regions or faint SNRs. A provisional calibration is provided by short measurements on a number of calibration sources before and after each 12 hour observation (Hunstead 1991).

The SMC has been gradually mapped over several years. The first observations were in 1981 (Mills et al. 1982). The performance of the MOST was improved in 1983 May and, over the next few years, observations covered an area containing almost all the emission nebulae in the SMC as catalogued by Davies, Elliott & Meaburn 1976. These data were used to study H II regions and SNRs (Ye 1988). A new survey was carried out between 1985 and 1992 (Turtle & Amy 1991; Ye & Turtle 1993). The partly overlapping fields were located on an array of pointing centres separated by 40 arcmin in declination and 10 minutes in right ascension, staggered by 5 minutes at adjacent declinations. Some additional fields were observed at non-standard centres where this improved the images of certain regions. All useful data acquired since mid-1983 have been included in the current data reduction. As a result the coverage of the survey area is not uniform; some central areas have been observed many times while peripheral regions may have been observed only once.

© Copyright Astronomical Society of Australia 1997