An Unusual High-Velocity Hydrogen Feature

Wannier, P. G.; Wrixon, G. T.

doi:10.1086/180930

Cited by 127 publications

(105 citation statements)

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“…The gas supply may also come from the Magellanic stream. The MW is surrounded by a long stream of neutral and ionized gas that is leading and trailing the Large and Small Magellanic Clouds (Wannier and Wrixon 1972;Mathewson et al 1974). This gas presumably came from the Magellanic clouds during their interaction with each other (Diaz and Bekki 2012) and is now experiencing a drag force from its motion in the hot MW halo gas (Mastropietro et al 2005).…”

Section: Neutral Gas Observationsmentioning

confidence: 99%

Star formation sustained by gas accretion

Alméida

Elmegreen

Muñoz–Tuñón

et al. 2014

Astron Astrophys Rev

178

130

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Numerical simulations predict that metal-poor gas accretion from the cosmic web fuels the formation of disk galaxies. This paper discusses how cosmic gas accretion controls star formation, and summarizes the physical properties expected for the cosmic gas accreted by galaxies. The paper also collects observational evidence for gas accretion sustaining star formation. It reviews evidence inferred from neutral and ionized hydrogen, as well as from stars. A number of properties characterizing large samples of star-forming galaxies can be explained by metal-poor gas accretion, in particular, the relationship among stellar mass, metallicity, and star-formation rate (the so-called fundamental metallicity relationship). They are put forward and analyzed. Theory predicts gas accretion to be particularly important at high redshift, so indications based on distant objects are reviewed, including the global star-formation history of the universe, and the gas around galaxies as inferred from absorption features in the spectra of background sources.

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Section: Neutral Gas Observationsmentioning

confidence: 99%

Star formation sustained by gas accretion

Alméida

Elmegreen

Muñoz–Tuñón

et al. 2014

Astron Astrophys Rev

178

130

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“…Magellanic longitude, L M ¼ 0 , is defined to correspond to the centre of the LMC. This is not the same coordinate system used by Wannier & Wrixon (1972). Individual channel maps of the region shown in Figure 5 are shown in the LSR velocity frame in Figure 6.…”

Section: The Magellanic Streammentioning

confidence: 99%

“…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%

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

Putman

Staveley‐Smith

Freeman

et al. 2003

ApJ

287

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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“…The accretion of gas from the two Magellanic Clouds by the MW has been considered as the origin of Magellanic Stream (Wannier, & Wrixon 1972;Fox et al 2010;Richter et al 2013).…”

Section: High Velocity O VImentioning

confidence: 99%