scholarly journals Molecular Clouds at High z

1991 ◽  
Vol 144 ◽  
pp. 41-51 ◽  
Author(s):  
Leo Blitz
Keyword(s):  
Sample Size ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Thin Disk ◽  
Galactic Latitude ◽  
High Galactic Latitude ◽  
Star Forming ◽  
Weak Evidence

The evidence for the existence of molecular clouds at large distances from the Galactic plane is reviewed. The molecular clouds at high Galactic latitudes are shown to be largely confined to the Galactic plane. There is evidence for one giant molecular cloud as much as four scale heights from the Galactic plane, but given the sample size from which the cloud is drawn, it is reasonable to suppose that it is part of the tail of the thin disk population. There is weak evidence that one star-forming molecular cloud may have originated in the Galactic halo. On the basis of kinematic evidence however, it is shown that there are three molecular clouds identified at high galactic latitude that, if not at high z, are likely to have resulted from interaction with gas in the halo. Understanding how these clouds have formed is likely to be an important key to understanding how the halo interacts with the disk gas.

scholarly journals Interstellar magnetic cannon targeting the Galactic halo

2018 ◽  
Vol 617 ◽  
pp. A101 ◽  
Author(s):  
J.-F. Robitaille ◽  
A. M. M. Scaife ◽  
E. Carretti ◽  
M. Haverkorn ◽  
R. M. Crocker ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Galactic Plane ◽  
Dust Emission ◽  
Galactic Centre ◽  
Gas Flows ◽  
Galactic Latitude ◽  
High Galactic Latitude ◽  
X Ray ◽  
North West ◽  
Hot Gas

We report the detection of a new Galactic bubble at the interface between the halo and the Galactic disc. We suggest that the nearby Lupus complex and parts of the Ophiuchus complex constitute the denser parts of the structure. This young bubble, ≲3 Myr old, could be the remnant of a supernova and it expands inside a larger HI loop that has been created by the outflows of the Upper Scorpius OB association. An HI cavity filled with hot X-ray gas is associated with the structure, which is consistent with the Galactic chimney scenario. The X-ray emission extends beyond the west and north-west edges of the bubble, suggesting that hot gas outflows are breaching the cavity, possibly through the fragmented Lupus complex. Analyses of the polarised radio synchrotron and of the polarised dust emission of the region suggest the connection of the Galactic centre spur with the young Galactic bubble. A distribution of HI clumps that spatially corresponds well to the cavity boundaries was found at VLSR ≃−100 km s−1. Some of these HI clumps are forming jets, which may arise from the fragmented part of the bubble. We suggest that these clumps might be “dripping” cold clouds from the shell walls inside the cavity that is filled with hot ionised gas. It is possible that some of these clumps are magnetised and were then accelerated by the compressed magnetic field at the edge of the cavity. Such a mechanism would challenge the Galactic accretion and fountain model, where high-velocity clouds are considered to be formed at high Galactic latitude from hot gas flows from the Galactic plane.

scholarly journals Correlation of Infrared Emission with H I and CO Gas in the High Latitude Cloud Area L1642

1990 ◽  
Vol 139 ◽  
pp. 216-217
Author(s):  
T. Liljeström ◽  
R. Laureijs
Keyword(s):  
Galactic Plane ◽  
Molecular Data ◽  
Infrared Emission ◽  
Galactic Latitude ◽  
Optical Extinction ◽  
Suitable Candidate ◽  
High Galactic Latitude ◽  
Dust Clouds ◽  
Background Gas ◽  
Co Gas

The high-galactic-latitude cloud L1642 (l = 210.8°, b = −36.7°) is a suitable candidate to relate IR measurements with atomic and molecular data because it has a reasonable size with respect to the rather poor (IRAS) IR resolution, a moderate optical extinction and an isolated location in the direction towards the galactic anticenter. The exceptionally high galactic latitude of −36.7° implies that L1642 is some 60 pc below the galactic plane (if r ≈ 100 pc is adopted for its distance). L1642 is thus sufficiently far off the galactic plane to minimize the confusion by background gas and dust clouds.

scholarly journals 2.3 GHz Radio Emission From Sco OB2

1980 ◽  
Vol 85 ◽  
pp. 105-106
Author(s):  
E.E. Baart ◽  
G. de Jager ◽  
P. I. Mountfort
Keyword(s):  
Star Formation ◽  
Radio Emission ◽  
Galactic Plane ◽  
Galactic Latitude ◽  
Dark Cloud ◽  
High Galactic Latitude ◽  
Lyman Continuum

The Sco OB2 Association is convenient for investigation as it has a high galactic latitude and is therefore remote from the confusion of the galactic plane. Its distance is accurately known and this permits fairly precise estimates to be made of the Lyman continuum photon fluxes responsible for the radio emission. It includes the ρ Ophiuci dark cloud where star formation is occurring.

scholarly journals Giant Molecular Clouds in the Galaxy: The Massachusetts-Stony Brook CO Galactic Plane Survey

1987 ◽  
Vol 115 ◽  
pp. 499-499 ◽  
Author(s):  
P. M. Solomon
Keyword(s):  
Molecular Clouds ◽  
Galactic Plane ◽  
Far Infrared ◽  
Formation Mechanisms ◽  
H Ii Regions ◽  
Giant Molecular Clouds ◽  
Star Forming ◽  
The Galaxy ◽  
Two Populations ◽  
Spiral Arm

The CO Galactic Plane Survey consists of 40,572 spectral line observations in the region between 1 = 8° to 90° and b = −1°.05 to +1°.05 spaced every 3 arc minutes, carried out with the FCRAO 14-m antenna. The velocity coverage from −100 to +200 km/s includes emission from all galactic radii. This high resolution survey was designed to observe and identify essentially all molecular clouds or cloud components larger than 10 parsecs in the inner galaxy. There are two populations of molecular clouds which separate according to temperature. The warm clouds are closely associated with H II regions, exhibit a non-axisymmetric galactic distribution and are a spiral arm population. The cold clouds are a disk population, are not confined to any patterns in longitude-velocity space and must be widespread in the galaxy both in and out of spiral arms. The correlation between far infrared luminosities from IRAS, and molecular masses from CO is utilized to determine a luminosity to mass ratio for the clouds. A face-on picture of the galaxy locating the warm population is presented, showing ring like or spiral arm features at R ∼ 5, 7.5 and 9 kpc. The cloud size and mass spectrum will be discussed and evidence presented showing the presence of clusters of giant molecular clouds with masses of 106 to 107 M⊙. The two populations of clouds probably have different star forming luminosity functions. The implication of the two populations for star formation mechanisms will be discussed.

Interstellar Reddening at High Galactic Latitudes

1973 ◽  
Vol 52 ◽  
pp. 263-267
Author(s):  
A. G. Davis Philip
Keyword(s):  
Main Sequence ◽  
Galactic Plane ◽  
Galactic Latitude ◽  
Early Type ◽  
High Galactic Latitude ◽  
Early Type Stars

Measures in the Strömgren four-color and Hβ systems provide an accurate way to determine color excesses of early-type stars. Fourteen areas at high galactic latitude have now been searched for faint A stars which are then measured photoelectrically to obtain the color excesses. Non-main sequence A stars, which are easily detected by means of the four-color photometry, are not included in the analysis. Within 40° of each pole, the reddening is essentially zero, Eb–y = 0.00 north of the galactic plane and Eb–y = 0.01 south of the plane.

scholarly journals Ammonia towards dust clumps in the giant molecular cloud associated with RCW 106

2012 ◽  
Vol 8 (S292) ◽  
pp. 50-50
Author(s):  
Vicki Lowe ◽  
Maria R. Cunningham ◽  
James S. Urquhart ◽  
Shinji Horiuchi
Keyword(s):  
Star Formation ◽  
Radio Telescope ◽  
Molecular Cloud ◽  
Galactic Plane ◽  
High Mass ◽  
Mass Star ◽  
Giant Molecular Clouds ◽  
Molecular Line ◽  
Star Forming ◽  
Star Formation Regions

AbstractHigh-mass stars are known to be born within giant molecular clouds (GMCs); However, the exact processes involved in forming a high-mass star are still not well understood. It is clear that high-mass stars do not form in isolation, and that the processes surrounding high-mass star formation may affect the environment of the entire molecular cloud. We are studying the GMC associated with RCW 106 (G333), which is one of the most active massive-star formation regions in the Galactic plane. This GMC, located at l = 333° b = − 0.5°, has been mapped in over 20 molecular line transitions with the Mopra radio telescope (83-110 GHz), in Australia, and with the Swedish-ESO Submillimeter Telescope (SEST) in the 1.2 mm cool dust continuum. The region is also within the Spitzer GLIMPSE infrared survey (3.6, 4.5, 5.8, and 8.0 μm) area. We have decomposed the dust continuum using a clump-finding algorithm (CLUMPFIND), and are using the multiple molecular line traditions from the Mopra radio telescope to classify the type and stage of star formation taking place therein. Having accurate physical temperatures of the star forming clumps is essential to constrain other parameters to within useful limits. To achieve this, we have obtained pointed NH3 observations from the Tidbinbilla 70-m radio telescope, in Australia, towards these clumps.

scholarly journals Structure formation in a colliding flow: The Herschel view of the Draco nebula

2017 ◽  
Vol 599 ◽  
pp. A109 ◽  
Author(s):  
M.-A. Miville-Deschênes ◽  
Q. Salomé ◽  
P. G. Martin ◽  
G. Joncas ◽  
K. Blagrave ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Molecular Clouds ◽  
Turbulent Energy ◽  
Small Scale ◽  
Neutral Medium ◽  
Galactic Latitude ◽  
High Galactic Latitude ◽  
Dissipation Scale ◽  
Scale Structures ◽  
Small Scale Structures

Context. The Draco nebula is a high Galactic latitude interstellar cloud observed at velocities corresponding to the intermediate velocity cloud regime. This nebula shows unusually strong CO emission and remarkably high-contrast small-scale structures for such a diffuse high Galactic latitude cloud. The 21 cm emission of the Draco nebula reveals that it is likely to have been formed by the collision of a cloud entering the disk of the Milky Way. Such physical conditions are ideal to study the formation of cold and dense gas in colliding flows of diffuse and warm gas. Aims. The objective of this study is to better understand the process of structure formation in a colliding flow and to describe the effects of matter entering the disk on the interstellar medium. Methods. We conducted Herschel-SPIRE observations of the Draco nebula. The clumpfind algorithm was used to identify and characterize the small-scale structures of the cloud. Results. The high-resolution SPIRE map reveals the fragmented structure of the interface between the infalling cloud and the Galactic layer. This front is characterized by a Rayleigh-Taylor (RT) instability structure. From the determination of the typical length of the periodic structure (2.2 pc) we estimated the gas kinematic viscosity. This allowed us to estimate the dissipation scale of the warm neutral medium (0.1 pc), which was found to be compatible with that expected if ambipolar diffusion were the main mechanism of turbulent energy dissipation. The statistical properties of the small-scale structures identified with clumpfind are found to be typical of that seen in molecular clouds and hydrodynamical turbulence in general. The density of the gas has a log-normal distribution with an average value of 103 cm-3. The typical size of the structures is 0.1−0.2 pc, but this estimate is limited by the resolution of the observations. The mass of these structures ranges from 0.2 to 20 M⊙ and the distribution of the more massive structures follows a power-law dN/ dlog (M) ~ M-1.4. We identify a mass-size relation with the same exponent as that found in molecular clouds (M ~ L2.3). On the other hand, we found that only 15% of the mass of the cloud is in gravitationally bound structures. Conclusions. We conclude that the collision of diffuse gas from the Galactic halo with the diffuse interstellar medium of the outer layer of the disk is an efficient mechanism for producing dense structures. The increase of pressure induced by the collision is strong enough to trigger the formation of cold neutral medium out of the warm gas. It is likely that ambipolar diffusion is the mechanism dominating the turbulent energy dissipation. In that case the cold structures are a few times larger than the energy dissipation scale. The dense structures of Draco are the result of the interplay between magnetohydrodynamical turbulence and thermal instability as self-gravity is not dominating the dynamics. Interestingly they have properties typical of those found in more classical molecular clouds.

scholarly journals IRAS 01005+7910, A High Galactic Latitude Post-AGB Star

2003 ◽  
Vol 209 ◽  
pp. 137-138
Author(s):  
Jingyao Hu
Keyword(s):  
Spectral Type ◽  
Planetary Nebula ◽  
Galactic Plane ◽  
Galactic Latitude ◽  
Chinese Journal ◽  
High Galactic Latitude ◽  
Optical Color ◽  
Astronomy And Astrophysics

Hu et al (1993) have selected a sample of proto-planetary nebula candidates based on the IRAS color-color diagram. IRAS 01005+7910 is one object of this sample. We have observed this object photometrically (Table 1) and spectroscopically (Fig. 1). From its spectral type of B2I and optical color of B - V = 0.23, we can derive the reddening as E(B - V) = 0.39 and interstellar/circumstellar absorption Av = 1.20. If it is a normal B-type supergiant, the distance module will be m - M = 16.05 and distance d = 16.2 kpc. Due to the galactic latitude b = 16.6, it should be located at about 4.6 kpcabove the galactic plane. This does not fit with normal B-type supergiant and we considered that it is a post-AGB star located at high galactic latitude. Recently Hrivnak et al (2000) found that this object shows carbon-rich features in the infrared. A paper on observations, reduction and discussions of this object has been submitted to the Chinese Journal of Astronomy and Astrophysics.

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