Linear polarization of millimeter-wave emission lines in clouds without large velocity gradients

1988 ◽  
Vol 328 ◽  
pp. 304 ◽  
Author(s):  
D. C. Lis ◽  
P. F. Goldsmith ◽  
R. L. Dickman ◽  
C. R. Predmore ◽  
A. Omont ◽  
...  
Keyword(s):  
Millimeter Wave ◽  
Linear Polarization ◽  
Emission Lines ◽  
Velocity Gradients ◽  
Large Velocity ◽  
Wave Emission

The polarization of millimeter-wave emission lines in dense interstellar clouds

1983 ◽  
Vol 267 ◽  
pp. 126 ◽  
Author(s):  
P. G. Wannier ◽  
N. Z. Scoville ◽  
R. Barvainis
Keyword(s):  
Millimeter Wave ◽  
Emission Lines ◽  
Interstellar Clouds ◽  
Wave Emission

scholarly journals A synergy of the velocity gradients technique and the probability density functions for identifying gravitational collapse in self-absorbing media

2021 ◽  
Vol 502 (2) ◽  
pp. 1768-1784
Author(s):  
Yue Hu ◽  
A Lazarian
Keyword(s):  
Magnetic Fields ◽  
Probability Density ◽  
Column Density ◽  
Mass Density ◽  
Probability Density Functions ◽  
Emission Lines ◽  
Density Functions ◽  
Star Forming ◽  
Velocity Gradients ◽  
Self Gravity

ABSTRACT The velocity gradients technique (VGT) and the probability density functions (PDFs) of mass density are tools to study turbulence, magnetic fields, and self-gravity in molecular clouds. However, self-absorption can significantly make the observed intensity different from the column density structures. In this work, we study the effects of self-absorption on the VGT and the intensity PDFs utilizing three synthetic emission lines of CO isotopologues 12CO (1–0), 13CO (1–0), and C18O (1–0). We confirm that the performance of VGT is insensitive to the radiative transfer effect. We numerically show the possibility of constructing 3D magnetic fields tomography through VGT. We find that the intensity PDFs change their shape from the pure lognormal to a distribution that exhibits a power-law tail depending on the optical depth for supersonic turbulence. We conclude the change of CO isotopologues’ intensity PDFs can be independent of self-gravity, which makes the intensity PDFs less reliable in identifying gravitational collapsing regions. We compute the intensity PDFs for a star-forming region NGC 1333 and find the change of intensity PDFs in observation agrees with our numerical results. The synergy of VGT and the column density PDFs confirms that the self-gravitating gas occupies a large volume in NGC 1333.

The Influence of Boundary Layer Velocity Gradients and Bed Proximity on Vortex Shedding From Free Spanning Pipelines

1984 ◽  
Vol 106 (1) ◽  
pp. 70-78 ◽  
Author(s):  
A. J. Grass ◽  
P. W. J. Raven ◽  
R. J. Stuart ◽  
J. A. Bray
Keyword(s):  
Boundary Layer ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Combined Effects ◽  
Maximum Increase ◽  
Velocity Gradients ◽  
Large Velocity ◽  
Layer Velocity ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

The paper summarizes the results of a laboratory study of the separate and combined effects of bed proximity and large velocity gradients on the frequency of vortex shedding from pipeline spans immersed in the thick boundary layers of tidal currents. This investigation forms part of a wider project concerned with the assessment of span stability. The measurements show that in the case of both sheared and uniform approach flows, with and without velocity gradients, respectively, the Strouhal number defining the vortex shedding frequency progressively increases as the gap between the pipe base and the bed is reduced below two pipe diameters. The maximum increase in vortex shedding Strouhal number, recorded close to the bed in an approach flow with large velocity gradients, was of the order of 25 percent.

scholarly journals Millimeter wave emission from a rotating electron ring in a rippled magnetic field

1984 ◽  
Vol 44 (3) ◽  
pp. 280-282 ◽  
Author(s):  
G. Bekefi ◽  
R. E. Shefer ◽  
W. W. Destler
Keyword(s):  
Magnetic Field ◽  
Millimeter Wave ◽  
Electron Ring ◽  
Wave Emission

scholarly journals Kinematics of Nuclei of Sc Galaxies

1980 ◽  
Vol 5 ◽  
pp. 191-191
Author(s):  
V. C. Rubin
Keyword(s):  
High Velocity ◽  
Stellar Population ◽  
Hii Regions ◽  
Emission Lines ◽  
High Luminosity ◽  
Rotation Curves ◽  
Velocity Gradients ◽  
Wide Range ◽  
Central Regions ◽  
Velocity Dispersions

For a sample of 21 Sc galaxies with a wide range of luminosities, of radii, and of masses, W. K. Ford and I have obtained spectra and determined rotation curves. By their kinematical behavior in their central regions, the Sc’s can be separated into two groups. Some galaxies, generally small and of low luminosity, have shallow central velocity gradients, reflecting their low central masses and densities. Other galaxies, most often large ones of high luminosity, have steep central velocity gradients. One reason this separation by central velocity gradients is of interest is because these galaxies exhibit other significant spectral differences which go hand-in-hand with the kinematical differences.The small, low luminosity galaxies show emission lines of Hα and [NII], with nuclear Ha sharp and stronger than [NII], and little or no stellar nuclear continuum, just as conventional HII regions. In contrast, the high luminosity galaxies show broad nuclear emission, with [NII] stronger than Ha. These galaxies have a strong red stellar continuum, arising from a red stellar population. The cause of the Hα[NII] intensity reversal in the nuclei of some galaxies remains unknown. However, the strong [NII] emission in generally high luminosity galaxies with massive nuclei, nuclei which show strong red continua, suggests that [Nil] intensity correlates with nuclear luminosity, and in turn with the density and velocity properties of the nuclear populations. We would expect high velocity dispersions and high bulge luminosities for galaxies with strong nuclear [NII] and steep central velocity gradients.

scholarly journals Millimeter-wave emission during the 2003 low excitation phase ofηCarinae

2005 ◽  
Vol 437 (3) ◽  
pp. 977-981 ◽  
Author(s):  
Z. Abraham ◽  
D. Falceta-Gonçalves ◽  
T. P. Dominici ◽  
L.-Å. Nyman ◽  
P. Durouchoux ◽  
...  
Keyword(s):  
Millimeter Wave ◽  
Wave Emission

Linear polarization characteristics for terrain identification at millimeter wave band

2014 ◽  
Vol 12 (10) ◽  
pp. 101201-101204
Author(s):  
Xuan Lu Xuan Lu ◽  
Zelong Xiao Zelong Xiao ◽  
Jianzhong Xu Jianzhong Xu
Keyword(s):  
Millimeter Wave ◽  
Linear Polarization ◽  
Wave Band ◽  
Millimeter Wave Band ◽  
Polarization Characteristics
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