Interstellar Neutral Hydrogen Emission Profile Structure

Verschuur, Gerrit L.

doi:10.1086/379957

Cited by 17 publications

(24 citation statements)

References 7 publications

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“…The energy equipartition assumption between thermal and turbulent kinetic energy is consistent with the turbulent velocity dispersions calculated for Galactic H i (Verschuur 2004;Haud & Kalberla 2007).…”

Section: Turbulence Setupsupporting

confidence: 81%

Formation of Cold Filamentary Structure From Wind-Blown Superbubbles

Ntormousi¹,

Burkert²,

Fierlinger³

et al. 2011

ApJ

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The expansion and collision of two wind-blown superbubbles is investigated numerically. Our models go beyond previous simulations of molecular cloud formation from converging gas flows by exploring this process with realistic flow parameters, sizes, and timescales. The superbubbles are blown by time-dependent winds and supernova explosions, calculated from population synthesis models. They expand into a uniform or turbulent diffuse medium. We find that dense, cold gas clumps and filaments form naturally in the compressed collision zone of the two superbubbles. Their shapes resemble the elongated, irregular structure of observed cold, molecular gas filaments, and clumps. At the end of the simulations, between 65% and 80% of the total gas mass in our simulation box is contained in these structures. The clumps are found in a variety of physical states, ranging from pressure equilibrium with the surrounding medium to highly underpressured clumps with large irregular internal motions and structures which are rotationally supported.

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Section: Turbulence Setupsupporting

confidence: 81%

Formation of Cold Filamentary Structure From Wind-Blown Superbubbles

Ntormousi¹,

Burkert²,

Fierlinger³

et al. 2011

ApJ

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“…The most striking feature present in the 350 MHz data is a ring-like structure which was first detected at 408 MHz in the late sixties (Bingham & Shakeshaft 1967) and then observed again at 21 cm with the Green Bank telescope (Verschuur 1969). In the 350 MHz data, the ring is mostly visible in polarization angle.…”

Section: Comparison With the 350 Mhz Wsrt Resultsmentioning

confidence: 86%

Foregrounds for observations of the cosmological 21 cm line

Bernardi¹,

Bruyn

Brentjens

et al. 2009

A&A

197

230

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Context. The cosmological 21 cm line promises to be a formidable tool for cosmology, allowing the investigation of the end of the so-called dark ages, when the first galaxies formed. Aims. Astrophysical foregrounds are expected to be about three orders of magnitude greater than the cosmological signal and therefore represent a serious contamination of the cosmological 21 cm line. Detailed knowledge of both their intensity and polarization structure on the relevant angular scale of 1-30 arcmin will be essential for extracting the cosmological signal from the data. Methods. We present the first results from a series of observations conducted with the Westerbork telescope in the 140-160 MHz range with a 2 arcmin resolution aimed at characterizing the properties of the foregrounds for epoch of reionization experiments. The polarization data were analysed through the rotation measure synthesis technique. We computed total intensity and polarization angular power spectra. Results. For the first time we have detected fluctuations in the Galactic diffuse emission on scales greater than 13 arcmin at 150 MHz, in the low Galactic latitude area known as Fan region, centred at α = 3 h 10 m , δ = 65 • 30 . Those fluctuations have an rms of 14 K. The total intensity power spectrum shows a power-law behaviour down to ∼900 with slope β I = −2.2 ± 0.3. The detection of diffuse emission at smaller angular scales is limited by residual point sources. We measured an rms confusion noise of ∼3 mJy beam −1 . Diffuse polarized emission was also detected for the first time at this frequency. The polarized signal shows complex structure both spatially and along the line of sight. The polarization power spectrum is not affected by residual point sources and is only limited by the thermal noise. It shows a power-law behaviour down to ∼2700 with slope β P = −1.65±0.15. The rms of polarization fluctuations is 7.2 K on 4 arcmin scales. Conclusions. The measured total intensity fluctuations are used to estimate the foreground contamination on the cosmological signal.By extrapolating the spectrum of total intensity emission, we find a contamination of δT = ( + 1)C I /2π ∼ 5.7 K on 5 arcmin scales and a corresponding rms value of ∼18.3 K at the same angular scale. The level of the polarization power spectrum is δT ∼ 3.3 K on 5 arcmin scales. However, the Fan region cannot be taken as representative of other sky regions, given its exceptionally bright polarized signal, but is likely to represent an upper limit on the sky brightness at moderate and high Galactic latitude.

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“…Recently published results of a more extensive study [2] confirm the existence of these linewidth families, which are most clearly seen in directions where the overall HI profiles have relatively low column densities, < 10 20 cm -2 .…”

Section: Introductionmentioning

confidence: 71%

“…Why do these histograms agree so closely, given that the data include only local HI at high galactic latitudes [2] while the CHVCs may be extragalactic? It is striking that the data in Fig.…”

Section: Linewidth Histogramsmentioning

confidence: 97%

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On the Critical Ionization Velocity Effect in Interstellar Space and Possible Detection of Related Continuum Emission

Verschuur

2007

IEEE Trans. Plasma Sci.

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be expected to produce locally enhanced electron densities where rapidly moving neutral gas masses interact with surrounding plasma. Evidence is presented that suggests that this phenomenon is occurring in interstellar space. It manifests as a spatial association between peaks in HI structure offset with respect to peaks in high-frequency radio continuum data obtained with the Wilkinson Microwave Anisotropy Probe.

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Interstellar Neutral Hydrogen Emission Profile Structure

Cited by 17 publications

References 7 publications

Formation of Cold Filamentary Structure From Wind-Blown Superbubbles

Formation of Cold Filamentary Structure From Wind-Blown Superbubbles

Foregrounds for observations of the cosmological 21 cm line

On the Critical Ionization Velocity Effect in Interstellar Space and Possible Detection of Related Continuum Emission

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