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High velocity gas that does not conform to Galactic rotation is observed throughout the Galaxy's halo. One component of this gas, HI high velocity clouds (HVCs), have attracted attention since their discovery in the 1960s and remain…

Astrophysics of Galaxies · Physics 2017-08-24 Asger Grønnow , Thor Tepper-García , Joss Bland-Hawthorn , Naomi McClure-Griffiths

The Draco nebula is a high Galactic latitude interstellar cloud likely to have been formed by the collision of a Galactic halo cloud entering the disk of the Milky Way. Such conditions are ideal to study the formation of cold and dense gas…

We have surveyed a ~0.9-square-degree area of the W3 giant molecular cloud and star-forming region in the 850-micron continuum, using the SCUBA bolometer array on the James Clerk Maxwell Telescope. A complete sample of 316 dense clumps was…

Astrophysics · Physics 2009-06-23 T J T Moore , D E Bretherton , T Fujiyoshi , N A Ridge , J Allsopp , M G Hoare , S L Lumsden , J S Richer

We found that an intermediate velocity cloud (IVC) IVC 86-36 in HI 21 cm emission shows a head-tail distribution toward the Galactic plane with marked parallel filamentary streamers, which is extended over 40 degrees in the sky. The…

The Galaxy's population of High Velocity Clouds (HVCs) may include a subpopulation that is confined by dark matter minihalos and falling toward the Galactic disk. We present the first magnetohydrodynamic simulational study of dark…

Astrophysics of Galaxies · Physics 2016-01-13 Jason Galyardt , Robin L. Shelton

We performed a search of star-forming sites influenced by external factors, such as SNRs, HII regions, and cloud-cloud collisions, to understand the star-forming activity in the Galactic center region using the NRO Galactic Center Survey in…

Astrophysics of Galaxies · Physics 2015-09-23 Masato Tsuboi , Atsushi Miyazaki , Kenta Uehara

We present the first interferometric CO(J=1->0) map of the entire H-alpha disk of M33. The 13" diameter synthesized beam corresponds to a linear resolution of 50 pc, sufficient to distinguish individual giant molecular clouds (GMCs). From…

Astrophysics · Physics 2009-11-10 G. Engargiola , R. Plambeck , E. Rosolowsky , L. Blitz

We use spectroscopic data from HST and FUSE to study the wide range of ionization states of the "highly ionized high-velocity clouds". Studied extensively in OVI absorption, these clouds are usually assumed to be infalling gas in the…

Astrophysics · Physics 2009-11-10 J. A. Collins , J. M. Shull , M. L. Giroux

Star formation occurs in molecular gas. In previous studies, the structure of the molecular gas has been studied in terms of molecular clouds, but has been overlooked beyond the cloud scale. We present an observational study of the…

Astrophysics of Galaxies · Physics 2013-11-01 Guang-Xing Li , Friedrich Wyrowski , Karl Menten , Arnaud Belloche

We have discovered an energetic high-velocity compact cloud CO$-$0.31+0.11 in the central molecular zone of our Galaxy. CO$-$0.31+0.11 is located at a projected distance of $\sim 45$ pc from the Galactic nucleus Sgr A$^*$. It is…

A population of discrete HI clouds in the halo of the inner Galaxy has been discovered in 21cm observations made with the Green Bank Telescope. The halo clouds are seen up to 1.5 kpc from the Galactic plane at many longitudes. Their…

Astrophysics · Physics 2009-11-07 Felix J. Lockman

Aims: We derive the 3-D HI volume density distribution for the Galactic disk out to R = 60 kpc. Methods: Our analysis is based on parameters for the warp and rotation curve derived previously. The data are taken from the…

Astrophysics · Physics 2015-05-13 P. M. W. Kalberla , L. Dedes

Studies of the Milky Way's disk-halo interface have historically identified inflowing and outflowing gas incompatible with disk rotation on the basis of radial velocity, leading to the well-known categories of intermediate-velocity clouds…

Data from the Canadian Galactic Plane Survey reveal an abundance of HI shells and arcs in the disk of our galaxy. While their shape is suggestive of stellar winds or supernovae influence, very few of these structures have been examined in…

Astrophysics · Physics 2015-06-24 Magdalen Normandeau , A. R. Taylor , P. E. Dewdney , Shantanu Basu

We present new observational results on high-velocity clouds (HVCs) based on an analysis of the Leiden/Dwingeloo HI survey. We cataloged all HVCs with NHI > 1 10^19 cm^-2 and found 252 clouds that form a representative flux limited sample.…

Astrophysics · Physics 2007-05-23 C. Bruens , J. Kerp , P. M. W. Kalberla , U. Mebold

Using 3D hydrodynamic calculations we simulate formation of molecular clouds in the Galaxy. The simulations take into account molecular hydrogen chemical kinetics, cooling and heating processes. Comprehensive gravitational potential…

Astrophysics of Galaxies · Physics 2015-06-05 S. A. Khoperskov , E. O. Vasiliev , A. M. Sobolev , A. V. Khoperskov

The Milky Way has a giant stellar structure in the solar neighborhood, which has a size of $\sim 1$ kpc, a mass of $\sim 10^6 {\rm M}_{\odot}$, and a ring-like distribution of young stars. Fundamental physical properties of this local…

Astrophysics of Galaxies · Physics 2015-05-13 Kenji Bekki

Observed HI accretion around nearby galaxies can only account for a fraction of the gas supply needed to sustain the currently observed star formation rates. It is possible that additional accretion happens in the form of low column density…

Astrophysics of Galaxies · Physics 2014-10-01 W. J. G. de Blok , Katie M. Keating , D. J. Pisano , F. Fraternali , F. Walter , T. Oosterloo , E. Brinks , F. Bigiel , A. Leroy

We have carried out high-resolution (~3') HI and CO line observations of GW46.4+5.5 and analyzed available IR and radio emission survey data. GW46.4+5.5 appears as a long filamentary structure extending vertically from the Galactic plane in…

Astrophysics · Physics 2009-10-31 Kee-Tae Kim , Bon-Chul Koo

Using 21cm HI observations from the Parkes Radio Telescope's Galactic All-Sky Survey, we measure 255 HI clouds in the lower Galactic halo that are located near the tangent points at 16.9 < l < 35.3 degrees and |b| < 20 degrees. The clouds…

Astrophysics of Galaxies · Physics 2015-05-19 H. Alyson Ford , Felix J. Lockman , N. M. McClure-Griffiths