Compact H<scp>i</scp>Clouds at High Forbidden Velocities in the Inner Galaxy

Stil, J. M.; Lockman, Felix J.; Taylor, A. R.; Dickey, John M.; Martín, P. G.; Rothwell, Timothy A.; Boothroyd, Arnold I.; McClure-Griffiths, N. M.

doi:10.1086/498347

Cited by 33 publications

(47 citation statements)

References 26 publications

(35 reference statements)

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“…For CW we used r ∼ 12 pc and for CE r ∼ 8 pc. We find a mass ranging from ∼(7-400) ×10 3 M for component CW, and ∼(1-60)×10 3 M for component CE, assuming spin temperatures ranging from 100 K to 6000 K. These masses are bigger than typical values of H i cloud masses of 60 M found in the Milky Way (Stil et al 2006). …”

Section: H I Absorptionmentioning

confidence: 51%

H I Observations of the Supermassive Binary Black Hole System in 0402+379

Rodriguez

Taylor

Zavala

et al. 2009

ApJ

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We have recently discovered a supermassive binary black hole system with a projected separation between the two black holes of 7.3 pc in the radio galaxy 0402+379 (Rodriguez et al. 2006). This is the most compact supermassive binary black hole pair yet imaged by more than two orders of magnitude. We present Global VLBI observations at 1.3464 GHz of this radio galaxy, taken to improve the quality of the H i data. Two absorption lines are found toward the southern jet of the source, one redshifted by 370 ± 10 km s −1 and the other blueshifted by 700 ± 10 km s −1 with respect to the systemic velocity of the source, which, along with the results obtained for the opacity distribution over the source, suggests the presence of two mass clumps rotating around the central region of the source. We propose a model consisting of a geometrically thick disk, of which we only see a couple of clumps, that reproduces the velocities measured from the H i absorption profiles. These clumps rotate in circular Keplerian orbits around an axis that crosses one of the supermassive black holes of the binary system in 0402+379. We find an upper limit for the inclination angle of the twin jets of the source to the line of sight of θ = 66 • , which, according to the proposed model, implies a lower limit on the central mass of ∼ 7 × 10 8 M and a lower limit for the scale height of the thick disk of ∼ 12 pc.

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Section: H I Absorptionmentioning

confidence: 51%

H I Observations of the Supermassive Binary Black Hole System in 0402+379

Rodriguez

Taylor

Zavala

et al. 2009

ApJ

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“…An inter-comparison of the main results from these authors is given in Table 3. Telescope independent quantities, like N HI and Δυ 1/2 , are found to be similar, with an exception of N HI from Stil et al (2006); the higher column densities in this sample can be explained by the low altitude of the sample. The other cloud properties are similar, which may imply that the different cloud samples in the inner and the outer Galaxy may have a similar origin.…”

Section: Comparison Between the Properties Of Different Samples Of H mentioning

confidence: 67%

“…Such a model would also explain the high kinetic energy which is needed for individual clouds to reach large z-distances. Support for such an interpretation comes from Stil et al (2006). They found fast moving clumps in the Galactic plane with velocity vectors located within the Galactic plane, analogous to fast velocities perpendicular to the plane as suggested as an explanation for the extra-planar gas layer.…”

Section: Introductionmentioning

confidence: 94%

“…The terminal velocity was used as well to determine the distance, since the clouds are located in the inner Galaxy. d) Stil et al (2006), where in the VLA Galactic Plane Survey (VGPS) 17 fast moving H i clouds were detected close to the plane which are possibly associated with the halo gas phase. An inter-comparison of the main results from these authors is given in Table 3.…”

Section: Comparison Between the Properties Of Different Samples Of H mentioning

confidence: 99%

“…Taking into account that the source distances are fairly similar, it is quite clear that the telescope used in each work may introduce a twofold systematic bias: a) synthesis telescopes work as spatial filters, more sensitive to cold compact (2006) 0.06-0.9 0.2-3 1-3 3-7.6 6-12 0.6-8 0. 03-7 Ford et al (2008) 0.3-1.7 0.4-6.6 5.8-26.2 46-100 120-4850 Stil et al (2006) 0.01-0.16 4.2-7.7 8-39 3.4-16.5 1.8-29.4 3.4-36.7 3-24 9-2500…”

Section: Comparison Between the Properties Of Different Samples Of H mentioning

confidence: 99%

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Properties of extra-planar H I clouds in the outer part of the Milky Way

Dedes

Kalberla

2010

A&A

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Context. There is mounting evidence for an extra-planar gas layer around the Milky Way disk, similar to the anomalous H i gas detected in a few other galaxies. As much as 10% of the gas may be in this phase. Aims.We analyze H i clouds located in the disk-halo interface outside the solar circle to probe the properties of the extra-planar H i gas, which is following Galactic rotation. Methods. We use the Leiden/Argentine/Bonn (LAB) 21-cm line survey to search for H i clouds which take part in the rotation of the Galactic plane, but are located above the disk layer. Selected regions are mapped with the Effelsberg 100-m telescope. Two of the H i halo clouds are studied in detail for their small scale structure using the Westerbork Synthesis Radio Telescope (WSRT) and the NRAO Very Large Array (VLA) .Results. Data from the 100 m telescope allow for the parameterization of 25 distinct H i halo clouds at Galactocentric radii 10 kpc < R <15 kpc and heights 1 kpc < z < 5 kpc. The clouds have a median temperature of 620 K, column densities of N HI ∼ 10 19 cm −2 , and most of them are surrounded by an extended envelope of warmer H i gas. Interferometer observations for two selected regions resolve the H i clouds into several arc-minute sized cores. These cores show narrow line widths (FWHM ∼ 3 km s −1 ), they have volume densities of n > 1.3 cm −3 , masses up to 24 M , and are on average in pressure equilibrium with the surrounding envelopes. Pressures and densities fall within the expectations from theoretical phase diagrams (P vs. n h ). The H i cores tend to be unstable if one assumes a thermally bistable medium, but are in better agreement with models that predict thermal fragmentation driven by a turbulent flow.

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High-resolution 21-cm observations of low-column density gas clumps in the Milky Way halo

Bekhti¹,

Richter²,

Winkel³

et al. 2009

A&A

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Aims. We study the properties of low-column density gas clumps in the halo of the Milky Way based on high-resolution 21-cm observations. Methods. Using interferometric data from the Westerbork Synthesis Radio Telescope (WSRT) and the Very Large Array (VLA), we studied H i emission at low-, intermediate-and high radial velocities along four lines of sight towards the quasars QSO J0003−2323, QSO B1331+170, QSO B0450−1310, and J081331+254503. Along these sightlines we had previously detected weak Ca ii and Na i absorbers in the optical spectra of these quasars.Results. The analysis of the high-resolution H i data reveals several compact and cold clumps of neutral gas at velocities similar to the optical absorption. The clumps have narrow H i line widths in the range of 1.8 ≤ v FWHM ≤ 13.0 km s Conclusions. Our high-resolution 21-cm observations indicate that many of the Ca ii and Na i absorbers seen in our optical quasar spectra are associated with low-column density H i clumps on small angular scales. This suggests that, next to the massive, highcolumn density neutral gas clouds in the halo (the common 21-cm low-, intermediate-, and high-velocity clouds, LVCs, IVCs, and HVCs), a population of low-mass, neutral gas structures exists in the halo and remain mostly unseen in the existing 21-cm all-sky surveys of IVCs and HVCs. One of our absorbers may be associated with the Magellanic Stream, two intermediate-velocity clouds are probably part of the Intermediate-Velocity Spur and the Low-latitude IV arch, respectively. The remaining systems could be located either in the lower halo or in the disk of the Milky Way. The estimated thermal gas pressures of the detected H i clumps are consistent with what is expected from theoretical models of gas in the inner and outer Milky Way halos.

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Compact HiClouds at High Forbidden Velocities in the Inner Galaxy

Cited by 33 publications

References 26 publications

H I Observations of the Supermassive Binary Black Hole System in 0402+379

H I Observations of the Supermassive Binary Black Hole System in 0402+379

Properties of extra-planar H I clouds in the outer part of the Milky Way

High-resolution 21-cm observations of low-column density gas clumps in the Milky Way halo

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