The Parkes HI Survey of the Magellanic System

We present the first fully and uniformly sampled, spatially complete HI survey of the entire Magellanic System with high velocity resolution, performed with the Parkes Telescope. The final data-cubes have an rms noise of sigma ~ 0.05 K and an effective angular resolution of 16 arcmin. The Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) are associated with huge gaseous features with a total HI mass of M(HI) = 4.87 10^8 M_sun [d/55 kpc]^2, if all HI gas is at the same distance of 55 kpc. Approximately two thirds of this HI gas is located close to the Magellanic Clouds (Magellanic Bridge and Interface Region), and 25% of the HI gas is associated with the Magellanic Stream. The Leading Arm has a four times lower HI mass than the Magellanic Stream, corresponding to 6% of the total HI mass of the gaseous features. We have analyzed the velocity field of the Magellanic Clouds and their neighborhood introducing a LMC-standard-of-rest frame. The HI in the Magellanic Bridge shows low velocities relative to the Magellanic Clouds suggesting an almost parallel motion, while the gas in the Interface Region has significantly higher relative velocities indicating that this gas is leaving the Magellanic Bridge building up a new section of the Magellanic Stream. The clouds in the Magellanic Stream and the Leading Arm show significant differences, both in the column density distribution and in the shapes of the line profiles. The HI gas in the Magellanic Stream is more smoothly distributed than the gas in the Leading Arm. These morphological differences can be explained if the Leading Arm is at considerably lower z-heights and embedded in a higher pressure ambient medium.Comment: 23 pages, 18 figures, accepted for publication in A&

A Molecular Cloud Forming in the Disk--Halo Interface

. We present medium and high angular resolution H I and CO observations of the galactic cirrus cloud IVC 135+54\Gamma45 and compare the line emission with intensities of the IRAS 100¯m and 60¯m bands. Its distance above the galactic plane is about 220 pc, thus well outside the scale height of normal molecular gas (ß 74 pc). Thus IVC 135+54\Gamma45 offers an unique possibility to study the cold interstellar medium in the transition zone between the galactic plane and the halo. We establish a linear relation between the IRAS 100¯m intensities and the proton column densities in the outer part of the cloud where the H 2 content is negligible. In the centre of the cloud we find two clumps which have more FIR-emission than can be accounted for by a linear N(H I)/I 100 correlation. The clumps are connected to H I filaments. A detailed analysis of one of the clumps reveals that the FIR-excess is associated mainly with the filament and to a lesser degree with the clump. This result is in contra..