Effelsberg H I observations of compact high-velocity clouds

Westmeier, T.; Brüns, C.; Kerp, J.

doi:10.1051/0004-6361:20041246

Cited by 41 publications

(66 citation statements)

References 20 publications

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“…• 1 (Putman et al 2002), while CHVC148 has an FWHM of ∼20 (Westmeier et al 2005). The uncertainty ellipses of these clouds take up a substantial fraction of the MIPS field; thus, the empty aperture method cannot be used to estimate flux uncertainties in these cases.…”

Section: Mid-ir Fluxes and Upper Limitsmentioning

confidence: 99%

ASPITZER-MIPS SEARCH FOR DUST IN COMPACT HIGH-VELOCITY H I CLOUDS

Williams¹,

Mathur²,

Poindexter³

et al. 2012

The Astronomical Journal

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We employ three-band Spitzer-MIPS observations to search for cold dust emission in three neutral hydrogen compact high-velocity clouds (CHVCs) in the vicinity of the Milky Way. Far-infrared emission correlated with H i column density was previously reported in HVC Complex C, indicating that this object contains dust heated by the Galactic radiation field at its distance of ∼10 kpc. Assuming published Spitzer, IRAS, and Planck, IR-H i correlations for Complex C, our Spitzer observations are of sufficient depth to directly detect 160 μm dust emission in the CHVCs if it is present at the same level as in Complex C, but no emission is detected in any of the targets. For one of the targets (CHVC289) which has well-localized H i clumps, we therefore conclude that it is fundamentally different from Complex C, with either a lower dust-to-gas ratio or a greater distance from the Galactic disk (and consequently cooler dust temperature). Firm conclusions cannot be drawn for the other two Spitzer-observed CHVCs since their small-scale H i structures are not sufficiently well known; nonetheless, no extended dust emission is apparent despite their relatively high H i column densities. The lack of dust emission in CHVC289 suggests that at least some compact high-velocity clouds objects may exhibit very low dust-to-gas ratios and/or greater Galactocentric distances than large HVC complexes.

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Section: Mid-ir Fluxes and Upper Limitsmentioning

confidence: 99%

ASPITZER-MIPS SEARCH FOR DUST IN COMPACT HIGH-VELOCITY H I CLOUDS

Williams¹,

Mathur²,

Poindexter³

et al. 2012

The Astronomical Journal

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“…The existence of a two-component gas structure is widely observed among HVCs and CHVCs (Cram & Giovanelli 1976;Wolfire et al 1995;Burton et al 2001;de Heij et al 2002;Braun & Burton 1999;Westmeier et al 2005). The 2D hydrostatic simulations of CHVCs by Sternberg et al (2002) are consistent with these observations.…”

Section: Evidence For Ram-pressure Interactionmentioning

confidence: 99%

Physical properties of two compact high-velocity clouds possibly associated with the leading arm of the Magellanic system

Bekhti

Brüns

Kerp

et al. 2006

A&A

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Aims. We observed two compact high-velocity clouds HVC 291+26+195 and HVC 297+09+253 to analyse their structure, dynamics, and physical parameters. In both cases there is evidence for an association with the Leading Arm of the Magellanic Clouds. The goal of our study is to learn more about the origin of the two CHVCs and to use them as probes for the structure and evolution of the Leading Arm. Methods. We have used the Parkes 64-m radio telescope and the Australia Telescope Compact Array (ATCA) to study the two CHVCs in the 21-cm line emission of neutral hydrogen. The observations with a single-dish and a synthesis telescope allow us to analyse both the diffuse, extended emission as well as the small-scale structure of the clouds. We present a method to estimate the distance of the two CHVCs.Results. The investigation of the line profiles of HVC 297+09+253 reveals the presence of two line components in the spectra which can be identified with a cold and a warm gas phase. In addition, we find a distinct head-tail structure in combination with a radial velocity gradient along the tail, suggesting a ram-pressure interaction of this cloud with an ambient medium. HVC 291+26+195 has only a cold gas phase and no head-tail structure. The ATCA data show several cold, compact clumps in both clouds which, in the case of HVC 297+09+253, are embedded in the warm, diffuse envelope. All these clumps have very narrow H i lines with typical line widths between 2 and 4 km s −1 FWHM, yielding an upper limit for the kinetic temperature of the gas of T max = 300 K. We obtain distance estimates for both CHVCs of the order of 10 to 60 kpc, providing additional evidence for an association of the clouds with the Leading Arm. Assuming a distance of 50 kpc, we get H i masses of 5.9 × 10 3 M and 4.0 × 10 4 M for HVC 291+26+195 and HVC 297+09+253, respectively.

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“…Figure 1 shows the Effelsberg observations of the CHVCs where it can be seen that CHVC 070+51-150 and CHVC 108-21-390 both exhibit a pronounced head-tail (HT) structure. In the case of CHVC 162+03-186 we find a socalled bow-shock shaped CHVC (Westmeier et al 2005b). The asymmetric appearance of the three CHVCs suggests a possible interaction with the ambient medium.…”

Section: Compact High-velocity Cloudsmentioning

confidence: 75%

“…Table 1 compiles the observational parameters while Table 2 summarizes the derived physical properties. Westmeier et al (2005b) found that CHVC 162+03-186 has a bow-shock shape (Fig. 1).…”

Section: Chvc 162+03-186mentioning

confidence: 95%

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H I observations of three compact high-velocity clouds around the Milky Way

Faridani¹,

Flöer²,

Kerp³

et al. 2014

A&A

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Context. We present deep H  observations of three compact high-velocity clouds (CHVCs).Aims. The main goal is to study their diffuse warm gas and compact cold cores. We use both low-and high-resolution data obtained with the 100 m Effelsberg telescope and the Westerbork Synthesis Radio Telescope (WSRT). The combination is essential in order to study the morphological properties of the clouds since the single-dish telescope lacks a sufficient angular resolution while the interferometer misses a large portion of the diffuse gas. Methods. Here single-dish and interferometer data are combined in the image domain with a new combination pipeline. The combination makes it possible to examine interactions between the clouds and their surrounding environment in great detail. Results. The apparent difference between single-dish and radio interferometer total flux densities shows that the CHVCs contain a considerable amount of diffuse gas with low brightness temperatures. A Gaussian decomposition indicates that the clouds consist predominantly of warm gas.

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Effelsberg H I observations of compact high-velocity clouds

Cited by 41 publications

References 20 publications

ASPITZER-MIPS SEARCH FOR DUST IN COMPACT HIGH-VELOCITY H I CLOUDS

ASPITZER-MIPS SEARCH FOR DUST IN COMPACT HIGH-VELOCITY H I CLOUDS

Physical properties of two compact high-velocity clouds possibly associated with the leading arm of the Magellanic system

H I observations of three compact high-velocity clouds around the Milky Way

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