Gas chromatography

Cram, Stuart P.; Juvet, Richard S.

doi:10.1021/ac60369a028

Cited by 19 publications

(10 citation statements)

References 191 publications

(204 reference statements)

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“…The broad line width features about 18 − 35 km s −1 wide are found to be associated with the pervasive filament while the narrow line width components from 4 to 7 km s −1 wide are the hallmark of the compact clouds. This is in close agreement with the results of Cram & Giovanelli (1976) whose study of several high-velocity features revealed two prominent line width regimes around 7 & 23 km s −1 wide. The data for A0 also reveal the existence of several distinct features with line widths between these two prominent values of order 12 km s −1 .…”

Section: Gaussian Analysis Of the Hi Profilessupporting

confidence: 92%

High-Resolution Observations and the Physics of High-Velocity Cloud A0

Verschuur

2013

ApJ

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The neutral hydrogen structure of high-velocity cloud A0 (at about −180 km s −1 ) has been mapped with a 9. 1 resolution. Gaussian decomposition of the profiles is used to separately map families of components defined by similarities in center velocities and line widths. About 70% of the HI gas is in the form of a narrow, twisted filament whose typical line widths are of order 24 km s −1 . Many bright features with narrow line widths of order 6 km s −1 , clouds, are located in and near the filament. A third category with properties between those of the filament and clouds appears in the data. The clouds are not always colocated with the broader line width filament emission as seen projected on the sky. Under the assumption that magnetic fields underlie the presence of the filament, a theorem is developed for its stability in terms of a toroidal magnetic field generated by the flow of gas along field lines. It is suggested that the axial magnetic field strength may be derived from the excess line width of the HI emission over and above that due to kinetic temperature by invoking the role of Alfvén waves that create what is in essence a form of magnetic turbulence. At a distance of 200 pc the axial and the derived toroidal magnetic field strengths in the filament are then about 6 µG while for the clouds they are about 4 µG. The dependence of the derived field strength on distance is discussed.

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Section: Gaussian Analysis Of the Hi Profilessupporting

confidence: 92%

High-Resolution Observations and the Physics of High-Velocity Cloud A0

Verschuur

2013

ApJ

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“…The two-phase structure of the H I lines from the core, also seen in other high-velocity clouds, suggests that it is in pressure equilibrium with a surrounding, low-density, medium (Cram & Giovanelli 1976;Ferrara & Field 1994). There is a group of H I features in the Complex at 130 • + 1 • that have a characteristic angular size of 4 ′ .…”

Section: Implied Properties Of Complex Hmentioning

confidence: 75%

High-Velocity Cloud Complex H: A Satellite of the Milky Way in a Retrograde Orbit?

Lockman

2003

ApJ

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Observations with the Green Bank Telescope of 21cm H I emission from the highvelocity cloud Complex H suggest that it is interacting with the Milky Way. A model in which the cloud is a satellite of the Galaxy in an inclined, retrograde circular orbit reproduces both the cloud's average velocity and its velocity gradient with latitude. The model places Complex H at R = 33 ± 9 kpc from the Galactic Center on a retrograde orbit inclined ≈ 45 • to the Galactic plane. At this location it has a mass in H I of > 6 × 10 6 M ⊙ and dimensions of at least 10 × 5 kpc. Some of the diffuse H I associated with the cloud has apparently been decelerated by interaction with Galactic gas. Complex H has similarities to the dwarf irregular galaxy Leo A and to some compact high-velocity clouds, and has an internal structure nearly identical to parts of the Magellanic Stream, with a pressure P/k ≈ 100 cm −3 K.

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“…The high-velocity H I seen directly toward Mrk 205 has been decomposed into two Gaussians with ∆v = 7.1 and 18.0 km s −1 . This direction provides an example of the multiple component (core-halo) structures found in some high-velocity spectra (Cram & Giovanelli 1976). The spectrum toward Mrk 205+, the only one in this Figure which is Hanning smoothed, contains a weak line with ∆v = 4 km s −1 , the narrowest in this survey.…”

Section: Sample Spectramentioning

confidence: 82%

“…The H I lines from some high-velocity clouds have two components at a similar velocity, one broad and one narrow (Cram & Giovanelli 1976;Braun & Burton 2000). This has been interpreted as evidence for a core-halo thermal structure in the clouds (Ferrara & Field 1994;Wakker & van Woerden 1997).…”

Section: Directions With Multiple Componentsmentioning

confidence: 99%

A Very Sensitive 21 centimeter Survey for Galactic High‐Velocity H i

Lockman¹,

Murphy²,

Petty-Powell³

et al. 2002

ASTROPHYS J SUPPL S

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Very sensitive H I 21cm observations have been made in 860 directions at δ ≥ −43 • in search of weak, Galactic, high-velocity H I emission lines at moderate and high Galactic latitudes. One-third of the observations were made toward extragalactic objects that are visible at optical and UV wavelengths. The median rms noise in the survey spectra is 3.4 mK, resulting in a median 4σ detection level of N HI = 8×10 17 cm −2 averaged over the 21 ′ beam of the telescope. High-velocity H I emission is detected in 37% of the directions; about half of the lines could not have been detected in previous surveys. The median FWHM of detected lines is 30.3 km s −1 . High-velocity H I lines are seen down to the sensitivity limit of the survey implying that there are likely lines at still lower values of N HI . The weakest lines have a kinematics and distribution on the sky similar to that of the strong lines, and thus do not appear to be a new population. Most of the

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Gas chromatography

Cited by 19 publications

References 191 publications

High-Resolution Observations and the Physics of High-Velocity Cloud A0

High-Resolution Observations and the Physics of High-Velocity Cloud A0

High-Velocity Cloud Complex H: A Satellite of the Milky Way in a Retrograde Orbit?

A Very Sensitive 21 centimeter Survey for Galactic High‐Velocity H i

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