Mapping Closure for Non-Gaussian Velocity Fields

2001 ◽  
pp. 243-248
Author(s):  
M. Takaoka
Keyword(s):  
Velocity Fields ◽  
Non Gaussian

GENERATION AND CHARACTERIZATION OF ABSOLUTE EQUILIBRIUM OF COMPRESSIBLE FLOWS

2009 ◽  
Vol 19 (10) ◽  
pp. 3445-3459 ◽  
Author(s):  
GIORGIO KRSTULOVIC ◽  
CARLOS CARTES ◽  
MARC BRACHET ◽  
ENRIQUE TIRAPEGUI
Keyword(s):  
Compressible Flows ◽  
Constant Pressure ◽  
Variable Temperature ◽  
Short Review ◽  
Velocity Fields ◽  
Incompressible Limit ◽  
Pressure Variable ◽  
Temperature Relaxation ◽  
Non Gaussian

A short review is given of recent papers on the relaxation to (incompressible) absolute equilibrium. A new algorithm to construct absolute equilibrium of spectrally truncated compressible flows is described. The algorithm uses stochastic processes based on the Clebsch representation of the velocity field to generate density and velocity fields that follow by construction the absolute equilibrium stationary probability. The new method is shown to reproduce the well-known Gaussian results in the incompressible limit. The irrotational compressible absolute equilibrium case is characterized and the distribution is shown to be non-Gaussian. The high-temperature compressible spectra are found not to obey k2 scaling. Finally, oscillating behavior in constant-pressure variable-temperature relaxation is obtained, suggesting the presence of second sound.

scholarly journals Turbulence in high latitude molecular clouds

2006 ◽  
Vol 2 (S237) ◽  
pp. 17-23
Author(s):  
S. N. Shore ◽  
T. N. LaRosa ◽  
L. Magnani ◽  
R. J. Chastain ◽  
F. Costagliola
Keyword(s):  
Coherent Structures ◽  
High Latitude ◽  
Molecular Clouds ◽  
Local Heating ◽  
Velocity Fields ◽  
Radiative Loss ◽  
Star Forming ◽  
Low Mass ◽  
Non Gaussian ◽  
Size Relation

AbstractWe summarize a continuing investigation of turbulence in high-latitude translucent molecular clouds. These low mass (~50–100 M), nearby (~100 pc), non-star forming clouds appear to be condensing out of the atomic cirrus. Unlike star-forming clouds the velocity fields in the clouds must be driven by external processes. Our detailed mapping of the clouds MBM 3,16 and 40 indicates that the dynamics in these clouds result from the combination of shear-flow and thermal instabilities, not shocks. These clouds also show coherent structures, non-Gaussian PDFs but no clear velocity-size relation. Lastly, the energetics of these clouds indicate that radiative loss may terminate the cascade before local heating takes place.

Models for non-Gaussian variation, with applications to turbulence

1979 ◽  
Vol 368 (1735) ◽  
pp. 501-520 ◽  
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Velocity Fields ◽  
Gaussian Distributions ◽  
One Dimensional ◽  
New Class ◽  
Stationary Stochastic Processes ◽  
High Reynolds ◽  
Exponential Power ◽  
Non Gaussian

A new class of distributions, generalizing the Gaussian, the hyperbolic, and the so-called exponential power distributions, is introduced and studied to some extent. In particular, the possibilities are discussed of representing the distributions as mixtures of Gaussian distributions and of constructing a certain kind of stationary stochastic processes whose one dimensional distributions are of the type considered. A brief survey is given of the literature on observed distributions of velocities and velocity derivatives from turbulent fields with high Reynolds number and the applicability of the proposed distributions and processes for modelling turbulent velocity fields is discussed.

Application of mapping closure to non-Gaussian velocity fields

1999 ◽  
Vol 11 (8) ◽  
pp. 2205-2214 ◽  
Author(s):  
M. Takaoka
Keyword(s):  
Velocity Fields ◽  
Non Gaussian

scholarly journals Physical Bayesian modelling of the non-linear matter distribution: New insights into the nearby universe

2019 ◽  
Vol 625 ◽  
pp. A64 ◽  
Author(s):  
J. Jasche ◽  
G. Lavaux
Keyword(s):  
Monte Carlo ◽  
Dark Matter ◽  
Structure Formation ◽  
Three Dimensional ◽  
Velocity Fields ◽  
Hierarchical Bayes ◽  
Coma Cluster ◽  
Matter Distribution ◽  
Non Linear ◽  
Non Gaussian

Accurate analyses of present and next-generation cosmological galaxy surveys require new ways to handle effects of non-linear gravitational structure formation processes in data. To address these needs we present an extension of our previously developed algorithm for Bayesian Origin Reconstruction from Galaxies (BORG) to analyse matter clustering at non-linear scales in observations. This is achieved by incorporating a numerical particle mesh model of gravitational structure formation into our Bayesian inference framework. The algorithm simultaneously infers the three-dimensional primordial matter fluctuations from which present non-linear observations formed and provides reconstructions of velocity fields and structure formation histories. The physical forward modelling approach automatically accounts for the non-Gaussian features in gravitationally evolved matter density fields and addresses the redshift space distortion problem associated with peculiar motions of observed galaxies. Our algorithm employs a hierarchical Bayes approach to jointly account for various observational effects, such as unknown galaxy biases, selection effects, and observational noise. Corresponding parameters of the data model are marginalized out via a sophisticated Markov chain Monte Carlo approach relying on a combination of a multiple block sampling framework and an efficient implementation of a Hamiltonian Monte Carlo sampler. We demonstrate the performance of the method by applying it to the 2M++ galaxy compilation, tracing the matter distribution of the nearby universe. We show accurate and detailed inferences of the three-dimensional non-linear dark matter distribution of the nearby universe. As exemplified in the case of the Coma cluster, our method provides complementary mass estimates that are compatible with those obtained from weak lensing and X-ray observations. For the first time, we also present a reconstruction of the vorticity of the non-linear velocity field from observations. In summary, our method provides plausible and very detailed inferences of the dark matter and velocity fields of our cosmic neighbourhood.

C. The Continuous Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 177-206
Author(s):  
J. B. Oke ◽  
C. A. Whitney
Keyword(s):  
Continuous Spectrum ◽  
Variable Stars ◽  
Velocity Fields ◽  
The Other ◽  
Line Spectrum ◽  
Direct Information ◽  
Thermodynamic Structure ◽  
Diagnostic Interpretation ◽  
Pulsating Variable Stars ◽  
The Continuum

Pecker:The topic to be considered today is the continuous spectrum of certain stars, whose variability we attribute to a pulsation of some part of their structure. Obviously, this continuous spectrum provides a test of the pulsation theory to the extent that the continuum is completely and accurately observed and that we can analyse it to infer the structure of the star producing it. The continuum is one of the two possible spectral observations; the other is the line spectrum. It is obvious that from studies of the continuum alone, we obtain no direct information on the velocity fields in the star. We obtain information only on the thermodynamic structure of the photospheric layers of these stars–the photospheric layers being defined as those from which the observed continuum directly arises. So the problems arising in a study of the continuum are of two general kinds: completeness of observation, and adequacy of diagnostic interpretation. I will make a few comments on these, then turn the meeting over to Oke and Whitney.

The Interpretation of Line Profiles

1977 ◽  
Vol 36 ◽  
pp. 191-215
Author(s):  
G.B. Rybicki
Keyword(s):  
Magnetic Fields ◽  
Atomic Physics ◽  
Velocity Fields ◽  
Spectral Lines ◽  
Inhomogeneous Structure ◽  
The Sun ◽  
Line Profiles ◽  
Physical Phenomena

Observations of the shapes and intensities of spectral lines provide a bounty of information about the outer layers of the sun. In order to utilize this information, however, one is faced with a seemingly monumental task. The sun’s chromosphere and corona are extremely complex, and the underlying physical phenomena are far from being understood. Velocity fields, magnetic fields, Inhomogeneous structure, hydromagnetic phenomena – these are some of the complications that must be faced. Other uncertainties involve the atomic physics upon which all of the deductions depend.

Central kiloparsec of NGC 1326 observed with SINFONI

2020 ◽  
Vol 638 ◽  
pp. A53
Author(s):  
Nastaran Fazeli ◽  
Gerold Busch ◽  
Andreas Eckart ◽  
Françoise Combes ◽  
Persis Misquitta ◽  
...  
Keyword(s):  
Black Hole ◽  
Galaxy Evolution ◽  
Near Infrared ◽  
Velocity Fields ◽  
Molecular Gas ◽  
Nearby Galaxy ◽  
Stellar Content ◽  
Stellar Rotation ◽  
Supermassive Black Hole ◽  
Integral Field Spectrograph

Gas inflow processes in the vicinity of galactic nuclei play a crucial role in galaxy evolution and supermassive black hole growth. Exploring the central kiloparsec of galaxies is essential to shed more light on this subject. We present near-infrared H- and K-band results of the nuclear region of the nearby galaxy NGC 1326, observed with the integral-field spectrograph SINFONI mounted on the Very Large Telescope. The field of view covers 9″ × 9″ (650 × 650 pc2). Our work is concentrated on excitation conditions, morphology, and stellar content. The nucleus of NGC 1326 was classified as a LINER, however in our data we observed an absence of ionised gas emission in the central r ∼ 3″. We studied the morphology by analysing the distribution of ionised and molecular gas, and thereby detected an elliptically shaped, circum-nuclear star-forming ring at a mean radius of 300 pc. We estimate the starburst regions in the ring to be young with dominating ages of < 10 Myr. The molecular gas distribution also reveals an elongated east to west central structure about 3″ in radius, where gas is excited by slow or mild shock mechanisms. We calculate the ionised gas mass of 8 × 105 M⊙ completely concentrated in the nuclear ring and the warm molecular gas mass of 187 M⊙, from which half is concentrated in the ring and the other half in the elongated central structure. The stellar velocity fields show pure rotation in the plane of the galaxy. The gas velocity fields show similar rotation in the ring, but in the central elongated H2 structure they show much higher amplitudes and indications of further deviation from the stellar rotation in the central 1″ aperture. We suggest that the central 6″ elongated H2 structure might be a fast-rotating central disc. The CO(3–2) emission observations with the Atacama Large Millimeter/submillimeter Array reveal a central 1″ torus. In the central 1″ of the H2 velocity field and residual maps, we find indications for a further decoupled structure closer to a nuclear disc, which could be identified with the torus surrounding the supermassive black hole.

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