From a comparison of radio and X-ray surveys of the MCs we find 71 sources in common towards the LMC and 27 sources in common towards the SMC. The sources in common towards the LMC are mainly SNRs and SNR candidates (36) and background sources (27). Out of 27 sources in common in the field of the SMC, 14 are SNRs, three are HII regions and eight are background sources.
We used the X-ray hardness ratio 2 (HR2) to help classify radio sources as SNRs or background sources using the fact that the previously known background sources have positive HR2.
Based on this classification we propose six new radio and X-ray sources as SNR candidates in the LMC (LMC B0530-6655, LMC B0534-7204, LMC B0528-6838, LMC B0542-6702, LMC B0544- 6910, LMC B0544-7030). Two SMC sources (SMC B0043-7330 and SMC B0054-7235) show characteristics typical for SNRs and therefore we classified them as SNR candidates.
From the number and radio flux densities of the LMC SNRs we derive an SNR
birth-rate of one every 
yr and an SFR of
for the LMC. Similarly,
for the SMC SNRs we find a birth-rate of one every
yr and an SFR of
.
Comparing the intensities (radio and X-ray) for the sources in common towards the MCs, we found very little correlation between radio and X-ray intensities densities but note that the strongest SNRs from this sample are young SNRs from Population I.
Acknowledgements
M.D.F. acknowledges an Australian Government Overseas Postgraduate Research Scholarship and considerable support from the Australia Telescope National Facility (CSIRO), the Max-Planck-Institut für Extraterrestrische Physik (MPE) and Max-Planck-Institut für Radioastronomie (MPIfR). This work is also supported by the Australian Research Council (ARC) and the ROSAT project is supported by the German Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF/DARA) and the Max-Planck-Gesellschaft. We thank J. Lequeux, Y.H. Chu, M. Ehle, D. Goddard, L. Staveley-Smith, D. Hartmann and J. Trümper for considerable support and comments on the manuscript.