We present first results of the H2O Southern Galactic Plane Survey (HOPS), using the Mopra Radio Telescope with a broad‐band backend and a beam size of about 2 arcmin. We have observed 100 deg2 of the southern Galactic plane at 12 mm (19.5–27.5 GHz), including spectral line emission from H2O masers, multiple metastable transitions of ammonia, cyanoacetylene, methanol and radio recombination lines. In this paper, we report on the characteristics of the survey and H2O maser emission. We find 540 H2O masers, of which 334 are new detections. The strongest maser is 3933 Jy and the weakest is 0.7 Jy, with 62 masers over 100 Jy. In 14 maser sites, the spread in the velocity of the H2O maser emission exceeds 100 km s−1. In one region, the H2O maser velocities are separated by 351.3 km s−1. The rms noise levels are typically between 1 and 2 Jy, with 95 per cent of the survey under 2 Jy. We estimate completeness limits of 98 per cent at around 8.4 Jy and 50 per cent at around 5.5 Jy. We estimate that there are between 800 and 1500 H2O masers in the Galaxy that are detectable in a survey with similar completeness limits to HOPS. We report possible masers in NH3 (11,9) and (8,6) emission towards G19.61−0.23 and in the NH3 (3,3) line towards G23.33−0.30.

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Abstract. We present a study of discrete radio sources in the Magellanic Clouds (MCs) using the latest large-scale radio surveys made with the Parkes radio telescope between 1.4 and 8.55 GHz. These surveys achieved higher sensitivity then previous surveys done with the Parkes telescope and so the number of discrete radio sources detected towards the MCs has increased by factor of five. Also, we have obtained improved positions, flux densities and radio spectral indices for all of these sources.A total of 483 sources towards the Large Magellanic Cloud (LMC) and 224 towards the Small Magellanic Cloud (SMC) have been detected at at least one radio frequency. Most of the MC's sources have been classified in one of three groups: SNRs, H ii regions or background sources according to classification criteria established here. In total, 209 discrete radio sources in the LMC and the 37 sources in the SMC are classified here to be either H ii regions or SNRs. We investigate their luminosity functions as well as the statistics of background sources behind the MCs. Also, we examine the distribution of SNRs and H ii regions in the MCs.

A total of 717 sources from the Australia Telescope Compact Array (ATCA) catalogue of the Small Magellanic Cloud (SMC) have been classified in Paper II (of this series) by Payne et al. Here, we present a statistical analysis of all 16 confirmed supernova remnants (SNRs) and five new candidate remnants. Included is a detailed discussion of the latter and three other sources that have some SNR characteristics. We have also found a new microquasar candidate (ATCA J005523−721055) in addition to ATCA J004718−723947 reported in Paper II. Source diameter comparisons suggest that SNRs as a group are of similar size in radio, optical and X‐ray with surface brightness values in the range of Galactic remnants. Remnant spectral indices, α[defined as Sν∝να, with Sν (flux density) and ν (frequency)], have a mean of −0.63 [standard deviation (s.d.) = 0.43] and ROSAT X‐ray hardness ratios confirm them to be soft X‐ray sources compared to background objects. We could not find any meaningful correlation between SNR surface brightness and diameter; we also discuss the number–diameter relation. A Venn diagram summarizes that most SNRs emit radiation in all three of the radio, optical and X‐ray domains. H ii region diameter comparisons between radio and optical sources show them to be a very diverse group that defies any simple relationship, preventing any meaningful calculation of flux density or spectral index. To better understand environments containing SNRs, we have scaled Hα images of four SMC regions and subtracted their flux from the ATCA 2.37‐GHz radio image. These 2.37 GHz–Hα subtraction (or difference) images reveal some new sources with predominantly non‐thermal emission, exposing SNRs confused with H ii regions.

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