Abstract. We present the first fully and uniformly sampled, spatially complete H survey of the entire Magellanic System with high velocity resolution (∆v = 1.0 km s −1 ), performed with the Parkes Telescope . Approximately 24 percent of the southern sky was covered by this survey on a ≈5 grid with an angular resolution of HPBW = 14. 1. A fully automated data-reduction scheme was developed for this survey to handle the large number of H spectra (1.5 × 10 6 ). The individual Hanning smoothed and polarization averaged spectra have an rms brightness temperature noise of σ = 0.12 K. The final data-cubes have an rms noise of σ rms ≈ 0.05 K and an effective angular resolution of ≈16 . In this paper we describe the survey parameters, the datareduction and the general distribution of the H gas. , if all H gas is at the same distance of 55 kpc. Approximately two thirds of this H gas is located close to the Magellanic Clouds (Magellanic Bridge and Interface Region), and 25% of the H gas is associated with the Magellanic Stream. The Leading Arm has a four times lower H mass than the Magellanic Stream, corresponding to 6% of the total H 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 H 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 Leading Arm is connected to the Magellanic Bridge close to an extended arm of the LMC. 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 H 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.
We present the HIPASS Bright Galaxy Catalog (BGC), which contains the 1000 H i brightest galaxies in the southern sky as obtained from the H i Parkes All-Sky Survey (HIPASS). The selection of the brightest sources is based on their H i peak flux density (S peak k116 mJy) as measured from the spatially integrated HIPASS spectrum. The derived H i masses range from $10 7 to 4 ; 10 10 M . While the BGC (z < 0:03) is complete in S peak , only a subset of $500 sources can be considered complete in integrated H i flux density (F H i k 25 Jy km s À1 ). The HIPASS BGC contains a total of 158 new redshifts. These belong to 91 new sources for which no optical or infrared counterparts have previously been cataloged, an additional 51 galaxies for which no redshifts were previously known, and 16 galaxies for which the cataloged optical velocities disagree. Of the 91 newly cataloged BGC sources, only four are definite H i clouds: while three are likely Magellanic debris with velocities around 400 km s À1 , one is a tidal cloud associated with the NGC 2442 galaxy group. The remaining 87 new BGC sources, the majority of which lie in the zone of avoidance, appear to be galaxies. We identified optical counterparts to all but one of the 30 new galaxies at Galactic latitudes jbj > 10 . Therefore, the BGC yields no evidence for a population of ''free-floating'' intergalactic H i clouds without associated optical counterparts. HIPASS provides a clear view of the local large-scale structure. The dominant features in the sky distribution of the BGC are the Supergalactic Plane and the Local Void. In addition, one can clearly see the Centaurus Wall, which connects via the Hydra and Antlia Clusters to the Puppis Filament. Some previously hardly noticable galaxy groups stand out quite distinctly in the H i sky distribution. Several new structures, including some not behind the Milky Way, are seen for the first time.
We present a Parkes multibeam H I survey of the Large Magellanic Cloud (LMC). This survey, which is sensitive to spatial structure in the range 200 pc to 10 kpc, complements the Australia Telescope Compact survey, which is sensitive to structure in the range 15-500 pc. With an rms column density sensitivity of 8 × 10 16 cm −2 for narrow lines and 4 × 10 17 cm −2 for typical linewidths of 40 km s −1 , emission is found to be extensive well beyond the main body of the LMC. Arm-like features extend from the LMC to join the Magellanic Bridge and the Leading Arm, a forward counterpart to the Magellanic Stream. These features, whilst not as dramatic as those in the Small Magellanic Cloud, appear to have a common origin in the Galactic tidal field, in agreement with recent 2MASS and DENIS results for the stellar population. The diffuse gas that surrounds the LMC, particularly at PAs of 90 • -330 • , appears to be loosely associated with tidal features, but loosening by the ram pressure of tenuous Galactic halo gas against the outer parts of the LMC cannot be discounted. High-velocity clouds, which lie between the Galaxy and the LMC in velocity and that appear in the ultraviolet spectra of some LMC stars, are found to be associated with the LMC if their heliocentric velocity exceeds approximately +100 km s −1 . They are possibly the product of energetic outflows from the LMC disc. The H I mass of the LMC is found to be (4.8 ± 0.2) × 10 8 M (for an assumed distance of 50 kpc), substantially more than previous recent measurements.
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