Intermediate-Velocity Gas in the North Galactic Hemisphere: H i Studies

Küntz, K. D.; Danly, L.

doi:10.1086/176765

Cited by 97 publications

(139 citation statements)

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“…The cloud's total mass is found to be in the range (0:2Y1:4) ; 10 4 M . We note that this is of the same order of magnitude as the ''Intermediate-Velocity Arch'' (IV Arch), the largest northern IVC (see Kuntz & Danly 1996;Wakker 2001Wakker , 2004, which also is moving toward the Galactic plane with a velocity of $40 km s À1 . It is also similar to the mass of the ''Low-Latitude IntermediateVelocity Arch'' (LLIV Arch), an IVC that is 0.9Y1.8 kpc distant with a mass of 1:5 ; 10 5 M .…”

Section: Location In the Milky Waymentioning

confidence: 69%

Distances to Galactic High‐Velocity Clouds. I. Cohen Stream, Complex GCP, Cloud g1

Wakker

York

Wilhelm

et al. 2008

ApJ

182

198

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The high-and intermediate-velocity interstellar clouds (HVCs/IVCs) are tracers of energetic processes in and around the Milky Way. Clouds with near-solar metallicity about 1 kpc above the disk trace the circulation of material between disk and halo (the Galactic fountain). The Magellanic Stream consists of gas tidally extracted from the SMC, tracing the dark matter potential of the Milky Way. Several other HVCs have low metallicity and appear to trace the continuing accretion of infalling intergalactic gas. These assertions are supported by the metallicities (0

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Section: Location In the Milky Waymentioning

confidence: 69%

Distances to Galactic High‐Velocity Clouds. I. Cohen Stream, Complex GCP, Cloud g1

Wakker

York

Wilhelm

et al. 2008

ApJ

182

198

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“…Using Hipparcos distances and stellar colours from the Tycho catalogue, plots of the distribution of interstellar reddening revealed several interesting, apparently nearby features with colour excesses much larger than the sample average. In particular, an anomalous reddening value was found for the small region (l = 145 • , b = +65 • ) that was tentatively associated with the IV Arch feature (Kuntz & Danly 1996) possibly located at a distance as close as 50 pc. The nearest sight-line to this position for which we have NaI data is towards HD 104241 (l = 150 • , b = +70 • ) with a distance of 175 pc.…”

Section: Comparison With Other Datamentioning

confidence: 88%

3D mapping of the dense interstellar gas around the Local Bubble

Lallement

Welsh

Vergely

et al. 2003

A&A

363

463

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Abstract. We present intermediate results from a long-term program of mapping the neutral absorption characteristics of the local interstellar medium, motivated by the availability of accurate and consistent parallaxes from the Hipparcos satellite. Equivalent widths of the interstellar NaI D-line doublet at 5890 Å are presented for the lines-of-sight towards some 311 new target stars lying within ∼350 pc of the Sun. Using these data, together with NaI absorption measurements towards a further ∼240 nearby targets published in the literature (for many of them, in the directions of molecular clouds), and the ∼450 linesof-sight already presented by , we show 3D absorption maps of the local distribution of neutral gas towards 1005 sight-lines with Hipparcos distances as viewed from a variety of different galactic projections. The data are synthesized by means of two complementary methods, (i) by mapping of iso-equivalent width contours, and (ii) by density distribution calculation from the inversion of column-densities, a method devised by Vergely et al. (2001). Our present data confirms the view that the local cavity is deficient in cold and neutral interstellar gas. The closest dense and cold gas "wall", in the first quadrant, is at ∼55-60 pc. There are a few isolated clouds at closer distance, if the detected absorption is not produced by circumstellar material. The maps reveal narrow or wide "interstellar tunnels" which connect the Local Bubble to surrounding cavities, as predicted by the model of Cox & Smith (1974). In particular, one of these tunnels, defined by stars at 300 to 600 pc from the Sun showing negligible sodium absorption, connects the well known CMa void , which is part of the Local Bubble, with the supershell GSH 238+00+09 (Heiles 1998). High latitude lines-of-sight with the smallest absorption are found in two "chimneys", whose directions are perpendicular to the Gould belt plane. The maps show that the Local Bubble is "squeezed" by surrounding shells in a complicated pattern and suggest that its pressure is smaller than in those expanding regions. We discuss the locations of several HI and molecular clouds. Using comparisons between NaI and HI or CO velocities, in some cases we are able to improve the constraints on their distances. According to the velocity criteria, MBM 33−37, MBM 16−18, UT 3−7, and MBM 54−55 are closer than ∼100 pc, and MBM 40 is closer than 80 pc. Dense HI clouds are seen at less than 90 pc and 85 pc in the directions of the MBM 12 and MBM 41−43 clouds respectively, but the molecular clouds themselves may be far beyond. The above closest molecular clouds are located at the neutral boundary of the Bubble. Only one translucent cloud, G192−67, is clearly embedded within the LB and well isolated. These maps of the distribution of local neutral interstellar NaI gas are also briefly compared with the distribution of both interstellar dust and neutral HI gas within 300 pc.

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“…The North Celestial Loop also overlaps spatially with the Low-Latitude Intermediate Velocity (LLIV) Arch (Kuntz & Danly 1996), an H i feature at slightly less negative velocity (∼−50 km s −1 ) than the IV Arch (∼−75 km s −1 ). The fields UMA and UMAEAST contain clumps identified by Kuntz & Danly (1996) as being part of the LLIV Arch (specifically LLIV1, LLIV2 and LLIV3). The field POL also contains emission that can be attributed to the LLIV Arch.…”

Section: Dust Propertiesmentioning

confidence: 94%

“…There appear to be differences among the IVCs too, perhaps related to the fact that they belong to different IVC complexes. All fields in our sample overlap with the Intermediate Velocity (IV) Arch, except MC which is in the southern Galactic sky and belongs to the PP Arch and BOOTES which is part of Complex K (Kuntz & Danly 1996). The North Celestial Loop also overlaps spatially with the Low-Latitude Intermediate Velocity (LLIV) Arch (Kuntz & Danly 1996), an H i feature at slightly less negative velocity (∼−50 km s −1 ) than the IV Arch (∼−75 km s −1 ).…”

Section: Dust Propertiesmentioning

confidence: 99%

“…All fields in our sample overlap with the Intermediate Velocity (IV) Arch, except MC which is in the southern Galactic sky and belongs to the PP Arch and BOOTES which is part of Complex K (Kuntz & Danly 1996). The North Celestial Loop also overlaps spatially with the Low-Latitude Intermediate Velocity (LLIV) Arch (Kuntz & Danly 1996), an H i feature at slightly less negative velocity (∼−50 km s −1 ) than the IV Arch (∼−75 km s −1 ). The fields UMA and UMAEAST contain clumps identified by Kuntz & Danly (1996) as being part of the LLIV Arch (specifically LLIV1, LLIV2 and LLIV3).…”

Section: Dust Propertiesmentioning

confidence: 99%

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Planckearly results. XXIV. Dust in the diffuse interstellar medium and the Galactic halo

Abergel

Ade

Aghanim

et al. 2011

A&A

183

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This paper presents the first results from a comparison of Planck dust maps at 353, 545 and 857 GHz, along with IRAS data at 3000 (100 μm) and 5000 GHz (60 μm), with Green Bank Telescope 21-cm observations of H i in 14 fields covering more than 800 deg 2 at high Galactic latitude. The main goal of this study is to estimate the far-infrared to sub-millimeter (submm) emissivity of dust in the diffuse local interstellar medium (ISM) and in the intermediate-velocity (IVC) and high-velocity clouds (HVC) of the Galactic halo. Galactic dust emission for fields with average H i column density lower than 2 × 10 20 cm −2 is well correlated with 21-cm emission because in such diffuse areas the hydrogen is predominantly in the neutral atomic phase. The residual emission in these fields, once the H i-correlated emission is removed, is consistent with the expected statistical properties of the cosmic infrared background fluctuations. The brighter fields in our sample, with an average H i column density greater than 2 × 10 20 cm −2 , show significant excess dust emission compared to the H i column density. Regions of excess lie in organized structures that suggest the presence of hydrogen in molecular form, though they are not always correlated with CO emission. In the higher H i column density fields the excess emission at 857 GHz is about 40% of that coming from the H i, but over all the high latitude fields surveyed the molecular mass faction is about 10%. Dust emission from IVCs is detected with high significance by this correlation analysis. Its spectral properties are consistent with, compared to the local ISM values, significantly hotter dust (T ∼ 20 K), lower submm dust opacity normalized per H-atom, and a relative abundance of very small grains to large grains about four times higher. These results are compatible with expectations for clouds that are part of the Galactic fountain in which there is dust shattering and fragmentation. Correlated dust emission in HVCs is not detected; the average of the 99.9% confidence upper limits to the emissivity is 0.15 times the local ISM value at 857 and 3000 GHz, in accordance with gas phase evidence for lower metallicity and depletion in these clouds. Unexpected anti-correlated variations of the dust temperature and emission cross-section per H atom are identified in the local ISM and IVCs, a trend that continues into molecular environments. This suggests that dust growth through aggregation, seen in molecular clouds, is active much earlier in the cloud condensation and star formation processes.

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Intermediate-Velocity Gas in the North Galactic Hemisphere: H i Studies

Cited by 97 publications

References 0 publications

Distances to Galactic High‐Velocity Clouds. I. Cohen Stream, Complex GCP, Cloud g1

Distances to Galactic High‐Velocity Clouds. I. Cohen Stream, Complex GCP, Cloud g1

3D mapping of the dense interstellar gas around the Local Bubble

Planckearly results. XXIV. Dust in the diffuse interstellar medium and the Galactic halo

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