Figure 1. The global distribution of H I in the Magellanic System in galactic coordinates. The Magellanic Stream (MS) is a thin (~10 degrees wide) tail of H I emanating from the Magellanic Clouds that trails for almost 100 degrees on the sky (Dec ~ -60 to +15 degrees). It is generally believed that the MS is the result of interactions between the Galaxy and the Clouds, but the exact form of these interactions still has not reached consensus. In the past, the MS was thought to be comprised of six different sections, but recent observations have shown that the Stream is a continuous body composed of clumps and filaments running parallel to the length of the Steam along its entire extent. The six sections are still used as reference. No star formation has been detected in the MS, making it the most primordial environment in the Local Group. Click on any figure to see an enlarged version.
We have mapped in neutral hydrogen (H I) two regions at the northern tip of the Magellanic Stream, known as MS V and MS VI, using the Arecibo telescope. The MS V region is located almost 80 degrees away from the Stream's head near the Magellanic Clouds, and shows a strong ridge of gas. Along its whole extent we find a bifurcation in velocity of ~25 km/s. This suggests the presence of two parallel sheets of gas, which meet together in several places by horseshoe-like features. The MS VI region, located 85 degrees away from the Stream's head, has a clumpy morphology. One of the clumps in this region shows a velocity gradient in the position-velocity slices, reminiscent of rotation curves seen in many galaxies.
Additionally, we determine the spatial power spectrum of the H I column density distribution in the MS VI region. The power spectrum can be fit by a power-law, having a slope of -3.7, reminiscent of a Kolmogorov fluid turbulence model. This fit indicates that there is a hierarchy of structure in the Stream. While this hierarchy has also been observed in the Milky Way and the Small Magellanic Cloud, it has generally been ascribed to interstellar turbulence. As there is no sign of star formation in the Magellanic Stream, the source of this hierarchy is still a mystery.