A Pervasive Broad Component in H I Emission Line Profiles: Temperature, Turbulence, or a Helium Signature?

Verschuur, Gerrit L.; Schmelz, J. T.

doi:10.1088/0004-6256/139/6/2410

Cited by 6 publications

(14 citation statements)

References 34 publications

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“…Several other families listed in Tables 1 & 2 include 1139 components with a weighted average line width of 14.6 ±1.2 km s −1 . Again, this value is significant when compared to the results summarized by Verschuur & Schmelz (2010) in their Table 3 of 13.9±0.9 km s −1 . For completeness, 10 entries in Tables 1 & 2 have W values between 4.1 & 8.1 km s −1 involving 923 components for a weighted average line width of 5.7±0.6 km s −1 .…”

Section: Sorting Gaussians Into Parameter Familiesmentioning

confidence: 54%

“…However, Gaussian analysis of HI profiles is difficult because a given solution may not be unique and that means that relatively few researchers have ventured into the realm of such analyses. The challenge has been discussed by Verschuur (2004), Verschuur & Peratt (1999), and Verschuur & Schmelz (2010). The algorithm used in the present Gaussian decomposition of LAB profiles was described by Verschuur (2004).…”

Section: Gaussian Analysismentioning

confidence: 99%

“…When compared to Gaussian line width data obtained from totally unrelated studies the numerical value for the broad component line width is striking. Verschuur & Schmelz (2010) gathered together line width data in their Table 2 pertaining to an underlying broad linewidth background component reported in 9 published papers by various researchers as well as their own data that together produced W = 33.7±2.4 km s −1 . This is essentially identical to the value of 33.1±1.1 km s −1 in the present study.…”

Section: Sorting Gaussians Into Parameter Familiesmentioning

confidence: 99%

“…This is essentially identical to the value of 33.1±1.1 km s −1 in the present study. [The possible role of a mysterious plasma phenomenon known as the Critical Ionization Velocity effect in affecting the line widths of the broad components is discussed by Verschuur (2007b) and Verschuur & Schmelz (2010) and references therein. Further consideration of that poorly understood phenomenon is beyond the scope of the present study.]…”

Section: Sorting Gaussians Into Parameter Familiesmentioning

confidence: 99%

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Interacting Galactic Neutral Hydrogen Filaments and Associated High-Frequency Continuum Emission

Verschuur

2013

ApJ

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Galactic HI emission profiles in an area where several large-scale filaments at velocities ranging from −46 km s −1 to 0 km s −1 overlap were decomposed into Gaussian components. Eighteen families of components defined by similarities of center velocity and line width were identified and related to small-scale structure in the high-frequency continuum emission observed by the WMAP spacecraft, as evidenced in the Internal Linear Combination (ILC) map of Hinshaw et al. (2007). When the center velocities of the Gaussian families, which summarize the properties of all the HI along the lines-of-sight in a given area, are used to focus on HI channel maps the phenomenon of close associations between HI and ILC peaks reported in previous papers is dramatically highlighted. Of particular interest, each of two pairs of HI peaks straddles a continuum peak. The previously hypothesized model for producing the continuum radiation (Verschuur, 2010) involving free-free emission from electrons is re-examined in the light of the new data. By choosing reasonable values for the parameters required to evaluate the model, the distance for associated HI−ILC features is of order 30 to 100 pc. No associated Hα radiation is expected because the electrons involved exist throughout the Milky Way. The mechanism for clumping and separation of neutrals and electrons needs to be explored.

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Section: Sorting Gaussians Into Parameter Familiesmentioning

confidence: 54%

Section: Gaussian Analysismentioning

confidence: 99%

Section: Sorting Gaussians Into Parameter Familiesmentioning

confidence: 99%

Section: Sorting Gaussians Into Parameter Familiesmentioning

confidence: 99%

See 2 more Smart Citations

Interacting Galactic Neutral Hydrogen Filaments and Associated High-Frequency Continuum Emission

Verschuur

2013

ApJ

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“…It is possible that turbulence has to be invoked to account for the non-thermal line widths but then it is necessary postulate that the turbulence is somehow quantized to account for the line widths of filament segments as opposed to the clouds. This problem was already discussed by Verschuur & Schmelz ( 2010) and in a similar vein a set of profiles toward A0 taken from the LAB survey of Kalberla et al (2005) were also decomposed into Gaussians. Again, an average line width of 24 km s −1 appears to underlie the profiles.…”

Section: The Temperature Of the Hi Gasmentioning

confidence: 89%

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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Critical Ionization Effect in Interstellar Clouds

Peratt

2014

Physics of the Plasma Universe

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A Pervasive Broad Component in H I Emission Line Profiles: Temperature, Turbulence, or a Helium Signature?

Cited by 6 publications

References 34 publications

Interacting Galactic Neutral Hydrogen Filaments and Associated High-Frequency Continuum Emission

Interacting Galactic Neutral Hydrogen Filaments and Associated High-Frequency Continuum Emission

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

Critical Ionization Effect in Interstellar Clouds

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