No abstract

SummaryA low resolution (2?2) survey of the neutral hydrogen in the Magellanic Clouds has produced two important additions to our knowledge of the system. (1) A bridge of gas between the Small and Large Cloud has been mapped. (2) The Small Cloud profiles show double peaks over a wide area, suggesting the possibility of two substantially separate masses of gas.The observations are discussed in terms of the distribution of integrated brightness and the median velocity of the H·line profiles. Contours of integrated brightness are compared with distributions ofHII regions and globular clusters. The overall mass of neutral hydrogen in the system is estimated at 109MO.The contours of median velocity reveal a rotation curve for the Large Cloud from which a total mass of 7 to 10 X 109MO is estimated for this galaxy.

SummaryA survey has been made of the 21 cm line from neutral interstellar hydrogen in the Magellanic Clouds. These are the fu;st observations of this radiation from an extragalactic source.The observations show that neutral hydrogen extends well beyond the easily visible regions of each Cloud, the gas being in each case less concentrated towards the nucleus than are the bright stars. From the total radiation received, the masses of neutral hydrogen are calculated to be 6 X 10 8 and 4 X 10 8 solar masses for the Large and Small Cloud respectively. Since the Small Cloud is believed to contain much less dust, this means that the ratio of gas to dust is very different in the two systems.The measurement of Doppler frequency shifts has yielded extensive new information about radial velocities within the Clouds. The velocity distribution indicates that both Clouds are rotating. Detailed discussion of the velocities has been deferred for subsequent pUblication.

The radial velocities measured in a survey of the 21 cm line from the Magellanic Clouds are discussed, principally in terms of the median velocity for each line profile. It is shown that each Cloud is rotating, and the analysis confirms the view, based on optical evidence, that the Clouds are flattened and tilted systems. The gas is probably the least flattened constituent of each Cloud and shows a large decrease of rotational speed with increasing distance from the equatorial plane.

No abstract