A radio continuum study of the Magellanic Clouds. I. Complete multi-frequency maps.
Abstract
New radio continuum and polarization surveys which completely cover both, the Large and the Small Magellanic Cloud (LMC and SMC), have been carried out recently at 2.45, 4.75, and 8.55 GHz, using the Parkes 64-m telescope. Here we shall present the results, along with a preliminary discussion of the radio morphology and the integrated radio continuum emission of the Clouds. It is argued that ram pressure effects caused by the motion of the LMC through the Milky Way halo are to some extent responsible for its overall radio morphology. Strong linear polarization is detected in the LMC (degrees of polarization reaching 25%), which appears to be associated with the region of highest HI and CO column densities. The observed degree of linear polarization implies a well-ordered magnetic field over kpc scales the alignment of which may also result from ram pressure effects. A preliminary analysis indicates a trailing spiral magnetic field the origin of which is as yet unclear. Only weak polarization (<= a few %) is seen in the SMC, possibly due to its large line-of-sight depth and complex structure. Large variations of the star formation efficiency across the LMC are disclosed by a radio-CO comparison. The integrated radio continuum spectra of the LMC and SMC are indicative of high relative amounts of thermal radio emission in these galaxies. Various impacts of the data base presented here for future studies are outlined.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- December 1991
- Bibcode:
- 1991A&A...252..475H
- Keywords:
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- Irregular Galaxies;
- Linear Polarization;
- Magellanic Clouds;
- Radio Astronomy;
- Radio Emission;
- Star Formation;
- Carbon Monoxide;
- Milky Way Galaxy;
- Astrophysics