scholarly journals The Extinction and Distance of the MBM Molecular Clouds at High Galactic Latitude

2021 ◽  
Vol 256 (2) ◽  
pp. 46
Author(s):  
Mingxu Sun ◽  
Biwei Jiang ◽  
He Zhao ◽  
Yi Ren
Keyword(s):  
Molecular Clouds ◽  
Galactic Latitude ◽  
High Galactic Latitude

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.

Discovery of WTTS candidates in high-galactic latitude translucent molecular clouds

1999 ◽  
Vol 44 (23) ◽  
pp. 2145-2149
Author(s):  
Jinzeng Li ◽  
Jingyao Hu ◽  
Wenping Chen
Keyword(s):  
Molecular Clouds ◽  
Galactic Latitude ◽  
High Galactic Latitude

Distances to the High Galactic Latitude Molecular Clouds G192−67 and MBM 23–24

1999 ◽  
Vol 516 (1) ◽  
pp. 243-249 ◽  
Author(s):  
Catherine E. Grant ◽  
David N. Burrows
Keyword(s):  
Molecular Clouds ◽  
Galactic Latitude ◽  
High Galactic Latitude

scholarly journals Quantifying the Magnetic Alignment of Hi and Dust in the Diffuse ISM

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
S.E. Clark ◽  
J.E.G. Peek ◽  
J. Colin Hill ◽  
M.E. Putman
Keyword(s):  
Magnetic Field ◽  
Molecular Clouds ◽  
Dust Emission ◽  
Neutral Hydrogen ◽  
Magnetic Alignment ◽  
Galactic Latitude ◽  
Linear Features ◽  
Filamentary Structure ◽  
High Galactic Latitude ◽  
Vision Algorithm

AbstractSensitive, high resolution observations of Galactic neutral hydrogen (Hi) reveal an intricate network of slender linear features, much as sensitive surveys of dust in Galactic molecular clouds reveal ubiquitous filamentary structure. Across the high Galactic latitude sky, diffuse Histructures are aligned with the interstellar magnetic field, as revealed by background starlight polarization (Clark, Peek, & Putman 2014) and by Planck 353 GHz polarized dust emission (Clark et al. 2015). These discoveries were enabled by the Rolling Hough Transform, a recently developed, open source machine vision algorithm.

scholarly journals Molecular Clouds Within 100 pc

1984 ◽  
Vol 81 ◽  
pp. 229-234
Author(s):  
Leo Blitz ◽  
Loris Magnani ◽  
Lee Mundy
Keyword(s):  
Interstellar Medium ◽  
Molecular Hydrogen ◽  
Molecular Clouds ◽  
Milky Way ◽  
Velocity Dispersion ◽  
Scale Height ◽  
Galactic Latitude ◽  
Local Interstellar Medium ◽  
High Galactic Latitude ◽  
The Mean

AbstractObservations at the 2.6 mm line of CO reveal the presence of a large number of molecular clouds at high galactic latitude. If the velocity dispersion of the clouds is a measure of their scale height, the mean distance of the ensemble we have detected is 100 pc. The clouds are unusual in that either they are not gravitationally bound or they are very deficient in CO relative to molecular hydrogen. These clouds represent a heretofore unrecognized component of the local interstellar medium. If they are pervasive in the Milky Way, they probably represent the small molecular cloud component of the interstellar medium.

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.

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