A Comparison of Discrete Sources in Radio and H surveys of the Magellanic Clouds - and the Potential for the New H Survey

Conclusions - and the Potential for the New H Survey

The comparison of Parkes radio surveys with the H surveys showed 180 and 40 sources in common to the LMC and SMC respectively. Most of these sources (95%) are intrinsic to the MCs as HII regions and SNRs. Some 61 sources in the LMC and seven sources in the SMC are classified on this basis as HII region candidates. Along with other criteria, such as X-ray detection, another 24 sources in the LMC and four in the SMC are classified as SNR candidates. A flux density comparison of the sources in common for the radio and H surveys, shows very good correlation for the sources intrinsic to the MCs.

Because these galaxies are relatively dust-free and the objects within them are at a well-defined distance, many of the problems that beset Galactic studies of large structures are greatly simplified. H images have already been very useful in studying nebulae in the MCs, revealing in particular old supergiant shells up to 1kpc across which appear to be associated with areas of recent star formation (Meaburn 1980; Hunter 1994). Furthermore, hundreds of HII regions and planetary nebulae have also been detected. A sensitive method has been found to search for, identify and separate SNRs from giant HII regions by a comparison of the H and radio continuum data (Ye et al. 1991). The new narrow-band of the H filters will exclude most background sources by virtue of the redshift. Another major use of an H survey of the MCs lies in its ability to locate sources more usually detected using objective prism spectroscopy, for example planetary nebulae, symbiotic and emission-line stars.

© Copyright Astronomical Society of Australia 1997