scholarly journals Fabry-Perot spectroscopy: a powerful method for detecting superbubbles in galaxy discs

2014 ◽  
Vol 10 (S309) ◽  
pp. 303-303
Author(s):  
A. Camps-Fariña ◽  
J. Beckman ◽  
J. Zaragoza-Cardiel ◽  
J. Font ◽  
K. Fathi
Keyword(s):  
Large Scale ◽  
Massive Star ◽  
Line Of Sight ◽  
Line Profiles ◽  
Large Scale Structures ◽  
Wide Range ◽  
Fabry Perot ◽  
Projection Effect ◽  
Scale Structures

AbstractWe present a new method for the detection and characterization of large scale expansion in galaxy discs based on Hα Fabry-Perot spectroscopy, taking advantage of the high spatial and velocity resolution of our instrument (GHαFaS). The method analyses multi-peaked emission line profiles to find expansion along the line of sight on a pixel-by-pixel basis. At this stage we have centred our attention on the large scale structures of expansive gas which show a coherent gradient of velocities from their centres as a result of both bubble shape and projection effect. The results show a wide range of expansion velocities in these superbubbles, ranging from 30-150 km/s, with the expected trend of finding the higher velocities in the more violent areas of the galaxies. We have applied the technique to the Antennae and M83, obtaining spectacular results, and used these to investigate to what extent kinematically derived ages can be found and used to characterize the ages of their massive star clusters.

scholarly journals STUDYING THE WHIM CONTENT OF LARGE-SCALE STRUCTURES ALONG THE LINE OF SIGHT TO H 2356-309

2010 ◽  
Vol 717 (1) ◽  
pp. 74-84 ◽  
Author(s):  
L. Zappacosta ◽  
F. Nicastro ◽  
R. Maiolino ◽  
G. Tagliaferri ◽  
D. A. Buote ◽  
...  
Keyword(s):  
Large Scale ◽  
Line Of Sight ◽  
Large Scale Structures ◽  
Scale Structures

scholarly journals Coherent large-scale structures from the linearized Navier–Stokes equations

2019 ◽  
Vol 873 ◽  
pp. 89-109 ◽  
Author(s):  
Anagha Madhusudanan ◽  
Simon. J. Illingworth ◽  
Ivan Marusic
Keyword(s):  
Large Scale ◽  
Eddy Viscosity ◽  
Stokes Equations ◽  
Turbulent Channel Flow ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Large Scale Structures ◽  
Viscosity Profile ◽  
Wide Range ◽  
Scale Structures

The wall-normal extent of the large-scale structures modelled by the linearized Navier–Stokes equations subject to stochastic forcing is directly compared to direct numerical simulation (DNS) data. A turbulent channel flow at a friction Reynolds number of $Re_{\unicode[STIX]{x1D70F}}=2000$ is considered. We use the two-dimensional (2-D) linear coherence spectrum (LCS) to perform the comparison over a wide range of energy-carrying streamwise and spanwise length scales. The study of the 2-D LCS from DNS indicates the presence of large-scale structures that are coherent over large wall-normal distances and that are self-similar. We find that, with the addition of an eddy viscosity profile, these features of the large-scale structures are captured by the linearized equations, except in the region close to the wall. To further study this coherence, a coherence-based estimation technique, spectral linear stochastic estimation, is used to build linear estimators from the linearized Navier–Stokes equations. The estimator uses the instantaneous streamwise velocity field or the 2-D streamwise energy spectrum at one wall-normal location (obtained from DNS) to predict the same quantity at a different wall-normal location. We find that the addition of an eddy viscosity profile significantly improves the estimation.

NON-THERMAL PHENOMENA IN GALAXY CLUSTERS

2012 ◽  
Vol 12 ◽  
pp. 280-289
Author(s):  
CHIARA FERRARI
Keyword(s):  
Galaxy Clusters ◽  
Large Scale ◽  
Thermal Component ◽  
X Ray ◽  
Large Scale Structures ◽  
Weak Magnetic Fields ◽  
Scale Structures ◽  
Thermal Phenomena ◽  
New Generation

The existence of cosmic rays and weak magnetic fields in the intracluster volume has been well proven by deep radio observations of galaxy clusters. However a detailed physical characterization of the non-thermal component of large scale-structures, relevant for high-precision cosmology, is still missing. I will show the importance of combining numerical and theoretical works with cluster observations by a new-generation of radio, Gamma- and X-ray instruments.

On the generation of large-scale eddy-driven patterns: the average eddy model

2016 ◽  
Vol 809 ◽  
pp. 316-344 ◽  
Author(s):  
Timour Radko
Keyword(s):  
Multiscale Analysis ◽  
Large Scale ◽  
Baroclinic Instability ◽  
Spontaneous Generation ◽  
Physical Processes ◽  
Layer System ◽  
Large Scale Structures ◽  
Wide Range ◽  
Scale Structures ◽  
Eddy Field

A theoretical model is developed which illustrates the dynamics of the spontaneous generation of large-scale structures in baroclinically unstable eddying flows. Techniques of asymptotic multiscale analysis are used to identify instabilities resulting from the positive feedback of the background eddies on large-scale perturbations. The novelty of the proposed approach lies in the choice of a dynamically consistent time-dependent background eddy field, which is taken from simulations of baroclinic instability in the Phillips two-layer system. The resulting solutions differ considerably from those of traditional multiscale models, in which the background eddy field is represented by steady analytical patterns. The present formulation makes it possible to (i) test the multiscale theory against the corresponding numerical simulations, (ii) unambiguously interpret the key physical processes at play and (iii) rationalize the emergence of large-scale patterns for certain background parameters. While the proposed approach to multiscale modelling is illustrated on a particular example of the Phillips baroclinic instability model, it is our belief that the presented technique is readily adaptable to a wide range of applications.

scholarly journals Overview of Uncovered and Suspected Large-scale Structures behind the Milky Way

1999 ◽  
Vol 16 (1) ◽  
pp. 53-59 ◽  
Author(s):  
Renée C. Kraan-Korteweg ◽  
Patrick A. Woudt
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Milky Way ◽  
Far Infrared ◽  
Observational Evidence ◽  
Large Scale Structures ◽  
Galaxy Distribution ◽  
Wide Range ◽  
Scale Structures ◽  
Zone Of Avoidance

AbstractVarious dynamically important extragalactic large-scale structures in the local Universe lie behind the Milky Way. Most of these structures (predicted and unexpected) have only recently been made ‘visible’ through dedicated deep surveys at various wavelengths. The wide range of observational searches (optical, near infrared, far infrared, radio and X-ray) for galaxies in the Zone of Avoidance (ZOA) will be reviewed and the uncovered and suspected large-scale structures summarised. Particular emphasis is given to the Great Attractor region where the existence of yet another cluster is suspected (Woudt 1998). Predictions from reconstructions of the density field in the ZOA are discussed and compared with observational evidence. Although no major structures are predicted out to about v ≲ 10,000 km s−1 for which no observational evidence exists, the comparison between reconstructed density fields and the observed galaxy distribution remain important as they allow derivations of the density and biasing parameters.

scholarly journals Decoupling local mechanics from large-scale structure in modular metamaterials

2017 ◽  
Vol 114 (14) ◽  
pp. 3590-3595 ◽  
Author(s):  
Nan Yang ◽  
Jesse L. Silverberg
Keyword(s):  
Mechanical Properties ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Design Parameters ◽  
Mechanical Function ◽  
Large Scale Structures ◽  
Mechanical Metamaterials ◽  
Wide Range ◽  
Scale Structures

A defining feature of mechanical metamaterials is that their properties are determined by the organization of internal structure instead of the raw fabrication materials. This shift of attention to engineering internal degrees of freedom has coaxed relatively simple materials into exhibiting a wide range of remarkable mechanical properties. For practical applications to be realized, however, this nascent understanding of metamaterial design must be translated into a capacity for engineering large-scale structures with prescribed mechanical functionality. Thus, the challenge is to systematically map desired functionality of large-scale structures backward into a design scheme while using finite parameter domains. Such “inverse design” is often complicated by the deep coupling between large-scale structure and local mechanical function, which limits the available design space. Here, we introduce a design strategy for constructing 1D, 2D, and 3D mechanical metamaterials inspired by modular origami and kirigami. Our approach is to assemble a number of modules into a voxelized large-scale structure, where the module’s design has a greater number of mechanical design parameters than the number of constraints imposed by bulk assembly. This inequality allows each voxel in the bulk structure to be uniquely assigned mechanical properties independent from its ability to connect and deform with its neighbors. In studying specific examples of large-scale metamaterial structures we show that a decoupling of global structure from local mechanical function allows for a variety of mechanically and topologically complex designs.

Characterization of large-scale structures in a forced ducted flow with dump

AIAA Journal ◽  
1987 ◽  
Vol 25 (9) ◽  
pp. 1164-1170 ◽  
Author(s):  
K. C. Schadow ◽  
K. J. Wilson ◽  
E. Gutmark
Keyword(s):  
Large Scale ◽  
Large Scale Structures ◽  
Scale Structures

Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1

1999 ◽  
Vol 173 ◽  
pp. 243-248
Author(s):  
D. Kubáček ◽  
A. Galád ◽  
A. Pravda
Keyword(s):  
Image Processing ◽  
Large Scale ◽  
Harvard College ◽  
Oak Ridge ◽  
Large Scale Structures ◽  
Short Period Comet ◽  
Short Period ◽  
Scale Structures ◽  
Harvard College Observatory ◽  
Period Comet

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.

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