scholarly journals Diffuse molecular clouds at high galactic latitude

1991 ◽  
Vol 147 ◽  
pp. 29-35 ◽  
Author(s):  
Ronald Stark
Keyword(s):  
Fine Structure ◽  
Molecular Clouds ◽  
Line Emission ◽  
Flux Ratio ◽  
Continuum Emission ◽  
Galactic Latitude ◽  
Filamentary Structure ◽  
High Galactic Latitude ◽  
O 63 ◽  
High Dust

The IRAS 60 and 100 μm flux from cirrus clouds are commonly explained by dust continuum emission. But this explanation in some cases requires unexpectedly high dust temperatures.We argue that the contribution of fine structure emission of neutral oxygen, O°(63 μm), can be significant in the IRAS 60 μm band. The 0°(63 μm) line emission together with the dust continuum emission offers a plausible explanation of the observed flux ratio I(60)/I(100), as well as of its variation across individual clouds. We also discuss the clumpy/filamentary structure of these clouds.

scholarly journals Diffuse molecular clouds at high galactic latitude

1991 ◽  
Vol 147 ◽  
pp. 29-35
Author(s):  
Ronald Stark
Keyword(s):  
Fine Structure ◽  
Molecular Clouds ◽  
Line Emission ◽  
Flux Ratio ◽  
Continuum Emission ◽  
Galactic Latitude ◽  
Filamentary Structure ◽  
High Galactic Latitude ◽  
O 63 ◽  
High Dust

The IRAS 60 and 100 μm flux from cirrus clouds are commonly explained by dust continuum emission. But this explanation in some cases requires unexpectedly high dust temperatures.We argue that the contribution of fine structure emission of neutral oxygen, O°(63 μm), can be significant in the IRAS 60 μm band. The 0°(63 μm) line emission together with the dust continuum emission offers a plausible explanation of the observed flux ratio I(60)/I(100), as well as of its variation across individual clouds. We also discuss the clumpy/filamentary structure of these clouds.

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 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 Extragalactic science with ALMA

2011 ◽  
Vol 7 (S284) ◽  
pp. 494-495
Author(s):  
George J. Bendo ◽  
Keyword(s):  
Molecular Clouds ◽  
High Redshift ◽  
Atacama Desert ◽  
Line Emission ◽  
Continuum Emission ◽  
Synchrotron Emission ◽  
Molecular Line ◽  
Molecular Lines ◽  
Nearby Galaxies ◽  
Detailed Imaging

AbstractThe Atacama Large Millimeter/submillimeter Array (ALMA) is a telescope comprising 66 antennas that is located in the Atacama Desert in Chile, one of the driest locations on Earth. When the telescope is fully operational, it will perform observations over ten receiver bands at wavelengths from 9.5-0.32 mm (31-950 GHz) with unprecedented sensitivities to continuum emission from cold (<20 K) dust, Bremsstrahlung, and synchrotron emission as well as submillimetre and millimetre molecular lines. With baselines out to 16km and dynamic reconfiguration, ALMA will achieve spatial resolutions ranging from 3″ to 0.010″, allowing for detailed imaging of continuum or molecular line emission from 0.1-1 kpc scale gas and dust discs in high-redshift sources or 10-100 pc scale molecular clouds and substructures within nearby galaxies. Science observations started on 30 September 2011 with 16 antennas and four receiver bands on baselines up to 400 m. The telescope's capabilities will steadily improve until full operations begin in 2013.

The Orion Molecular Clouds OMC‐1 and OMC‐2 Mapped in the Far‐Infrared Fine‐Structure Line Emission of C+and O0

1997 ◽  
Vol 481 (1) ◽  
pp. 343-354 ◽  
Author(s):  
F. Herrmann ◽  
S. C. Madden ◽  
T. Nikola ◽  
A. Poglitsch ◽  
R. Timmermann ◽  
...  
Keyword(s):  
Fine Structure ◽  
Molecular Clouds ◽  
Line Emission ◽  
Far Infrared ◽  
Structure Line

scholarly journals Star Formation in Quasar Host Galaxies at Redshift 6: Millimeter Surveys and New Insights from ALMA

2012 ◽  
Vol 8 (S292) ◽  
pp. 184-187
Author(s):  
Ran Wang ◽  
Jeff Wagg ◽  
Chris L. Carilli ◽  
Fabian Walter ◽  
Xiaohui Fan ◽  
...  
Keyword(s):  
Fine Structure ◽  
Star Formation ◽  
Massive Star ◽  
Line Emission ◽  
Continuum Emission ◽  
Molecular Gas ◽  
Host Galaxies ◽  
Massive Star Formation ◽  
Systematic Survey ◽  
Structure Line

AbstractWe have been carrying out a systematic survey of the star formation and ISM properties in the host galaxies of z∼6 quasars. Our 250 GHz observations, together with available data from the literature, yield a sample of 14 z∼6 quasars that are bright in millimeter dust continuum emission with estimated FIR luminosities of a few 1012 to 1013 L⊙. Most of these millimeter-detected z∼6 quasars have also been detected in molecular CO line emission, indicating molecular gas masses on order of 1010 M⊙. We have searched for [C II] 158 micron fine structure line emission toward four of the millimeter bright z∼6 quasars with ALMA and all of them have been detected. All these results suggest massive star formation at rates of about 600 to 2000 M⊙ yr−1 over the central few kpc region of these quasar host galaxies.

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