A new general survey of high-velocity neutral hydrogen in the Southern Hemisphere

Bajaja, E.; Nicolau, C. E. Cappa de; Cersósimo, J. C.; Martín, M. C.; Loiseau, N.; Morras, R.; Olano, C. A.; Poêppel, W. G. L.

doi:10.1086/191033

Cited by 61 publications

(57 citation statements)

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“…Pieces of these structures were first seen by van Kuilenburg (1972) and . Although there was no direct connection, Mathewson et al (1974) suggested a possible association of these features to the MCs and this hypothesis was further explored by Mathewson et al (1979), Morras (1982), and Bajaja et al (1989). With reprocessed HIPASS data Putman et al (1998) demonstrated that the LAF gas is indeed associated with the Magellanic Clouds and is an extension of the Magellanic Stream.…”

Section: The Source Of the Leading Arm Feature (Laf)mentioning

confidence: 98%

The Origin of the Magellanic Stream and its Leading Arm

Nidever

Majewski

Burton

2008

Astrophysics and Space Science Proceedings

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We explore the Magellanic Stream (MS) using a Gaussian decomposition of the H I velocity profiles in the Leiden-Argentine-Bonn (LAB) all-sky H I survey. This decomposition exposes the MS to be composed of two filaments distinct both spatially (as first pointed out by Putman et al.) and in velocity. Using the velocity coherence of the filaments, one can be traced back to its origin in what we identify as the SouthEast H I Overdensity (SEHO) of the Large Magellanic Cloud (LMC), which includes 30 Doradus. Parts of the Leading Arm (LA) can also be traced back to the SEHO in velocity and position. Therefore, at least one-half of the trailing Stream and most of the LA originates in the LMC, contrary to previous assertions that both the MS and the LA originate in the Small Magellanic Cloud (SMC) and/or in the Magellanic Bridge. The two MS filaments show strong periodic, undulating spatial and velocity patterns that we speculate are an imprint of the LMC rotation curve. If true, then the drift rate of the Stream gas away from the Magellanic Clouds is ∼49 km s −1 and the age of the MS is ∼1.74 Gyr. The Staveley-Smith et al. high-resolution H I data of the LMC show gas outflows from supergiant shells in the SEHO that seem to be creating the LA and LMC filament of the MS. Blowout of LMC gas is an effect not previously accounted for but one that probably plays an important role in creating the MS and LA.

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Section: The Source Of the Leading Arm Feature (Laf)mentioning

confidence: 98%

The Origin of the Magellanic Stream and its Leading Arm

Nidever

Majewski

Burton

2008

Astrophysics and Space Science Proceedings

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“…Uncovering the Magellanic Stream and its surroundings is crucial to the understanding of the formation and evolution of not only the Milky Way, but the entire Local Group, yet until the present paper, the neutral hydrogen data for the entire Stream and its surroundings remained severely undersampled (e.g., Mathewson et al 1974;Bajaja et al 1985). Sections of the Stream have been observed at higher spatial or velocity resolution (e.g., Cohen 1982;Haynes 1979;Morras 1983Morras , 1985Wayte 1989), but these observations focused on small regions within the main filament of the Stream originally presented by Mathewson et al Here we present H i maps of the entire Magellanic Stream and its surroundings at 15<5 resolution (equivalent to 250 pc at 55 kpc) using data from the H i Parkes All Sky Survey (HIPASS; 5 Barnes et al 2001).…”

Section: Introductionmentioning

confidence: 94%

The Magellanic Stream, High‐Velocity Clouds, and the Sculptor Group

Putman

Staveley‐Smith

Freeman

et al. 2003

ApJ

286

401

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The Magellanic Stream is a 100 Â 10 filament of gas that lies within the Galactic halo and contains $2 Â 10 8 M of neutral hydrogen. In this paper we present data from the H i Parkes All Sky Survey (HIPASS) in the first complete survey of the entire Magellanic Stream and its surroundings. We also present a summary of the reprocessing techniques used to recover large-scale structure in the Stream. The substantial improvement in spatial resolution and angular coverage compared to previous surveys reveals a variety of prominent features, including bifurcation along the main Stream filament; dense, isolated clouds that follow the entire length of the Stream; head-tail structures; and a complex filamentary web at the head of the Stream where gas is being freshly stripped away from the Small Magellanic Cloud and the Bridge. Debris that appears to be of Magellanic origin extends out to 20 from the main Stream filaments. The Magellanic Stream has a velocity gradient of 700 km s À1 from the Clouds to the tail of the Stream, $390 km s À1 greater than that due to Galactic rotation alone, therefore implying a noncircular orbit. The dual filaments comprising the Stream are likely to be relics from gas stripped separately from the Magellanic Bridge and the SMC. This implies that (1) the Bridge is somewhat older than conventionally assumed; and (2) the Clouds have been bound together for at least one or two orbits. The transverse velocity gradient of the Stream also appears to support long-term binary motion of the Clouds. A significant number of the most elongated cataloged Stream clouds (containing $1% of the Stream mass) have position angles aligned along the Stream. This suggests the presence of shearing motions within the Stream, arising from tidal forces or interaction with the tenuous Galactic halo. As previously noted, clouds within one region of the Stream, along the sight line to the less distant half (southern half on the sky) of the Sculptor Group, show anomalous properties. There are more clouds along this sight line than any other part of the Stream, and their velocity distribution significantly deviates from the gradient along the Stream. We argue that this deviation could be due to a combination of halo material, and not to distant Sculptor clouds, based on a spatial and kinematic comparison between the Sculptor Group galaxies and the anomalous clouds and the lack of cloud detection in the northern half of the group. This result has significant implications for the hypothesis that there might exist distant, massive high-velocity clouds within the Local Group. Cataloged clouds within the Magellanic Stream do not have a preferred scale size. Their mass spectrum f ðM H i Þ / M À2:0 H i and column density spectrum f ðN H i Þ / N À2:8 H i are steep compared with Ly absorbers and galaxies, and similar to the anomalous clouds along the Sculptor Group sight line.

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“…• by 1 • grid; the southern material of Bajaja et al (1985) was observed on the IAR 100-foot telescope at somewhat lower rms sensitivity then the Hulsbosch & Wakker survey and at comparable velocity resolution, but on a coarser initial sampling grid of 2…”

Section: Observationsmentioning

confidence: 99%

An automated search for compact high–velocity clouds in the Leiden/Dwingeloo Survey

Heij

Braun²,

Burton

2002

A&A

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Abstract.We describe an automated search through the Leiden/Dwingeloo H  Survey (LDS) for high-velocity clouds north of δ = −28• . From the general catalog we extract a sample of relatively small (less than about 8• ) and isolated high-velocity clouds, CHVCs: anomalous-velocity H  clouds which are sharply bounded in angular extent with no kinematic or spatial connection to other H  features down to a limiting column density of 1.5 × 10 18 cm −2 . This column density is an order of magnitude lower than the critical H  column density, ∼2 × 10 19 cm −2 , (e.g. Maloney 1993) where the ionized fraction is thought to increase dramatically due to the extragalactic radiation field. As such, these objects are likely to provide their own shielding to ionizing radiation. Their small angular size, of less than about 1• FWHM, might then imply substantial distances, since the partially ionized H  skin in a power-law ionizing photon field has a typical exponential scale-length of 1 kpc (e.g. Corbelli & Salpeter 1993). The automated search algorithm has been applied to the HIPASS and to the Leiden/Dwingeloo data sets. The results from the LDS are described here; Putman et al. (2002) describe application of this algorithm to the HIPASS material. We identify 67 CHVCs in the LDS which satisfy stringent requirements on isolation, and an additional 49 objects which satisfy somewhat less stringent requirements. Independent confirmation is available for all of these objects, either from earlier data in the literature or from new observations made with the Westerbork Synthesis Radio Telescope and reported here. The catalog includes 54 of the 65 CHVCs listed by on the basis of a visual search of the LDS data.

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A new general survey of high-velocity neutral hydrogen in the Southern Hemisphere

Cited by 61 publications

References 0 publications

The Origin of the Magellanic Stream and its Leading Arm

The Origin of the Magellanic Stream and its Leading Arm

The Magellanic Stream, High‐Velocity Clouds, and the Sculptor Group

An automated search for compact high–velocity clouds in the Leiden/Dwingeloo Survey

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