2 Discrete sources towards the Magellanic Clouds

2.1 Radio data

Catalogues of discrete radio sources towards the LMC at six radio frequencies are presented in Papers IV and IVa of this series and in Filipovic (1996). The total number of catalogued radio sources is 483. The common area of the radio and IR surveys ($\sim$100 square degrees) lies between RA(B1950)=04$\rm ^h$23$\rm ^m$ to 06$\rm ^h$14$\rm ^m$ and Dec(B1950)=-64$^\circ$ to -74$^\circ$.

The new catalogues of radio sources in the SMC at five radio frequencies are given in Paper V and in Filipovic (1996). There is a total of 224 radio sources towards the SMC. The area that these catalogues cover is $\sim$42 square degrees between RA(B1950)=00$\rm ^h$12$\rm ^m$ to 01$\rm ^h$38$\rm ^m$ and Dec(B1950)=-69$^\circ$40$^\prime$  to -76$^\circ$20$^\prime$.

As clear radio detections, we listed only radio sources that are stronger than 5$\sigma$ or seen in at least two frequencies.

2.2 Infrared data

The IRAS surveyed in a uniform fashion most of the sky in four photometric bands centred at 12, 25, 60 and 100 $\mu$m. These observations provide a remarkable data-base for investigating discrete sources, star-formation regions and dust properties in galaxies. This is because the mid- and far-infrared (MIR and FIR) emission from galaxies, as measured by IRAS, is mostly caused by thermal radiation from interstellar dust grains heated by starlight. The MIR and FIR thus probe directly the dust properties, the mix of dust temperatures and young stellar populations responsible for most of the dynamics in the interstellar radiation field.

An atlas and catalogues of IR sources in the MCs were published by Schwering & Israel (1990) and further information about MC IR surveys can be found there. Altogether, some 1891 LMC and 249 SMC sources were listed in this study. Also as a check on the Schwering & Israel (1990) catalogues we have used the IRAS FITS images obtained from Skyview (http://skview.gsfc.nasa.gov/skyview.html).

The angular resolution of the IRAS maps of the MCs was not precisely known, owing to their special beam pattern (Meylnik & Rice 1990). Because of the method used to deconvolve the dirty IRAS beam it was known only that the maps at four IR frequencies have equal resolution. On this assumption and the known positions of K and M stars from the SAO catalogue we fitted some of the bright stars in the 12-$\mu$m image with a two-dimensional Gaussian fitting routine. The resolution derived by this method is 3.7$^\prime$ for the original maps.

A large fraction of sources listed in Schwering & Israel (1990) catalogues could not be identified in the IRAS FITS images. Therefore, it is very difficult to estimate a number of sources that have positional coincidence by chance alignment.