Intergalactic H I in the sculptor group

Mathewson, D. S.; Cleary, M. N.; Murray, J. D.

doi:10.1086/181719

Cited by 46 publications

(48 citation statements)

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“…This is still substantial ($390 km s À1 ) and indicates that there are noncircular motions present. Mathewson et al (1974) point out that this variation in radial velocity is what is expected if the gas is in a Keplerian orbit and seen from a focus.…”

Section: The Magellanic Streamsupporting

confidence: 54%

“…This group of clouds happens to lie in the same region as the southern (on the sky) and near half of the Sculptor Group. Mathewson et al (1975) were the first to point out the coincidence between these anomalous velocity clouds and the Sculptor Group galaxies. They argued that the clouds toward the galaxies NGC 55 and 300 were associated with the Sculptor Group rather than the Magellanic Stream based on the kinematic and positional similarities.…”

Section: Origin Of the Clouds Along The Sight Line To The Sculptor Groupmentioning

confidence: 95%

“…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: 93%

“…The most famous Galactic halo H i stream is the Magellanic Stream. Discovered 30 years ago (Wannier & Wrixon 1972;Mathewson et al 1974), this complex arc of neutral hydrogen starts from the Magellanic Clouds and continues for over 100 through the south Galactic pole. It has been created through the interaction of our Galaxy with the Magellanic Clouds and may represent a recent example of the accretion and merging process that created the Milky Way.…”

Section: Introductionmentioning

confidence: 99%

“…This, together with the low velocities of the Sculptor Group galaxies (down to 70 km s À1 ), makes it very difficult to distinguish how much of the high-velocity neutral hydrogen is directly related to the Magellanic Stream and how much may be intra-Sculptor Group/Local Group material. Mathewson et al (1975) was the first to argue that some of the H i clouds along the sight line to the Magellanic Stream do not seem to fit into the normal velocity distribution of the Stream and may be associated with Sculptor Group galaxies. This was countered by Haynes & Roberts (1979) and Haynes (1979), who argued that it is merely a spatial coincidence.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: The Magellanic Streamsupporting

confidence: 54%

Section: Origin Of the Clouds Along The Sight Line To The Sculptor Groupmentioning

confidence: 95%