Bulk Motion of Galaxies and Hubble Flow Anisotropy on a Scale of 100 Mpc

2005 ◽  
Vol 201 ◽  
pp. 501-502
Author(s):  
S. L. Parnovsky ◽  
V. E. Karachentseva ◽  
Yu. N. Kudrya ◽  
I. D. Karachentsev
Keyword(s):  
Velocity Field ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Dipole Component ◽  
Bulk Motion ◽  
Flow Anisotropy ◽  
Strong Dipole ◽  
Hubble Flow

We study a large-scale bulk motion of thin edge-on spiral galaxies from the RFGC catalogue using a multipole decomposition of velocity field. The quadrupole and octupole components are statistically significant. The first one corresponds to the Hubble flow anisotropy, the second one leads to decrease of modulus of dipole component due to the strong dipole-octupole interaction.

Dipole bulk velocity based on new data sample of galaxies from the catalogue 2MFGC

2017 ◽  
Vol 7 (1-2) ◽  
pp. 6-11 ◽  
Author(s):  
M. Vasylenko ◽  
Yu. Kudrya
Keyword(s):  
Velocity Field ◽  
Microwave Radiation ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Dipole Component ◽  
Bulk Motion ◽  
Sky Survey ◽  
Extended Sources ◽  
Fisher Relation ◽  
Cosmic Microwave Radiation

We use the 2MFGC catalogue for investigation of large-scale flows on the basis of the Tully-Fisher relation (TFR). The catalogue contains 18020 galaxies selected from the extended sources of the infrared sky survey 2MASS XSC. The majority of galaxies in the catalogue are spiral galaxies of late morphological types whose discs are visible almost from the edge. For more than a decade of the catalogue usage, the number of galaxies in HyperLEDA database with the measured radial velocities and rotational velocities (that are necessary to construct the TFR) has been increased by about 17%. In this paper, an updated working sample of 2MFGC galaxies is presented and earlier results are revised taking into account new data. We have confined ourselves to comparison of only the "old" and "new" parameters of the dipole component of the velocity field. The dipole bulk motion of galaxies of this sample with respect to cosmic microwave radiation is characterised by a velocity of V=264±36 km/s in the direction l=308°±8°, b=-16°±6°.

Spiral Galaxies, Elliptical Galaxies and the Large-Scale Velocity Field Within 3500 Km/s of the Local Group

1988 ◽  
pp. 177-180 ◽  
Author(s):  
David Burstein ◽  
Roger L. Davies ◽  
Alan Dressler ◽  
S. M. Faber ◽  
Donald Lynden-Bell ◽  
...  
Keyword(s):  
Velocity Field ◽  
Large Scale ◽  
Local Group ◽  
Spiral Galaxies ◽  
Elliptical Galaxies

scholarly journals Spiral Galaxies and the Peculiar Velocity Field

1996 ◽  
Vol 168 ◽  
pp. 183-191 ◽  
Author(s):  
Riccardo Giovanelli ◽  
Martha P. Haynes ◽  
Pierre Chamaraux ◽  
Luiz N. Da Costa ◽  
Wolfram Freudling ◽  
...  
Keyword(s):  
Velocity Field ◽  
Reference Frame ◽  
Large Scale ◽  
Local Group ◽  
Spiral Galaxies ◽  
Density Parameter ◽  
Compelling Evidence ◽  
Homogeneous Sample ◽  
Peculiar Velocity ◽  
Peculiar Velocities

We report results of a redshift-independent distance measurement survey that extends to all sky and out to a redshift of approximately 7500 km s−1. Tully–Fisher (TF) distances for a homogeneous sample of 1600 late spiral galaxies are used to analyze the peculiar velocity field. We find large peculiar velocities in the neighborhood of superclusters, such as Perseus–Pisces (PP) and Hydra–Centaurus, but the main clusters embedded in those regions appear to be virtually at rest in the CMB reference frame. We find no compelling evidence for large-scale bulk flows, whereby the Local Group, Hydra–Cen and PP would share a motion of several hundred km s−1with respect to the CMB. Denser sampling in the PP region allows a clear detection of infall and backflow motions, which can be used to map the mass distribution in the supercluster and to obtain an estimate of the cosmological density parameter.

scholarly journals Relativistic approach to the kinematics of large-scale peculiar motions

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
Eleni Tsaprazi ◽  
Christos G. Tsagas
Keyword(s):  
Velocity Field ◽  
Growth Rates ◽  
Large Scale ◽  
Cosmological Perturbation ◽  
Cosmological Perturbation Theory ◽  
Peculiar Velocity ◽  
Linear Evolution ◽  
Peculiar Velocities ◽  
Bulk Motion ◽  
Relativistic Approach

Abstract We consider the linear kinematics of large-scale peculiar motions in a perturbed Friedmann universe. In so doing, we take the viewpoint of the “real” observers that move along with the peculiar flow, relative to the smooth Hubble expansion. Using relativistic cosmological perturbation theory, we study the linear evolution of the peculiar velocity field, as well as the expansion/contraction, the shear and the rotation of the bulk motion. Our solutions show growth rates considerably stronger than those of the earlier treatments, which were mostly Newtonian. On scales near and beyond the Hubble radius, namely at the long-wavelength limit, peculiar velocities are found to grow as $$a^2$$a2, in terms of the scale factor, instead of the Newtonian $$a^{1/2}$$a1/2-law. We attribute this to the fact that, in general relativity, the energy flux, triggered here by the peculiar motion of the matter, also contributes to the local gravitational field. In a sense, the bulk flow gravitates, an effect that has been bypassed in related relativistic studies. These stronger growth-rates imply faster peculiar velocities at horizon crossing and higher residual values for the peculiar-velocity field. Alternatively, one could say that our study favours bulk peculiar flows larger and faster than anticipated.

scholarly journals Spiral Galaxies, Elliptical Galaxies and the Large-Scale Velocity Field Within 3500 km/s of the Local Group

1988 ◽  
Vol 130 ◽  
pp. 177-180
Author(s):  
David Burstein ◽  
Roger L. Davies ◽  
Alan Dressler ◽  
S.M. Faber ◽  
Donald Lynden-Bell ◽  
...  
Keyword(s):  
Velocity Field ◽  
Mass Concentration ◽  
Large Scale ◽  
Field Model ◽  
Local Group ◽  
Spiral Galaxies ◽  
Independent Sets ◽  
Elliptical Galaxies ◽  
Substantial Agreement ◽  
Model Predictions

The peculiar motions for spiral galaxies and elliptical galaxies within V = 3500 km/s are compared to the model predictions of the mass concentration (MC) velocity field model of Lynden-Bell et al. The large-scale motions defined by over 600 galaxies from three independent sets of data (Aaronson et al.; de Vaucouleurs and Peters and elliptical galaxies) are in substantial agreement with this model.

scholarly journals Large Scale Magnetohydrodynamical Considerations in Spiral Galaxies

1983 ◽  
Vol 100 ◽  
pp. 157-158
Author(s):  
E. Battaner ◽  
M. L. Sánchez-Saavedra
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Velocity Field ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Galactic Center ◽  
Galactic Plane ◽  
Interstellar Gas ◽  
Plasma Distribution ◽  
Ring Structures

A magnetohydrodynamical result is deduced, which could contribute to our understanding of spiral and ring structures in galaxies. The usual expressions for the continuity, momentum and induction equations are adopted for the gas of a galaxy, and the following simplifying hypotesis are made : a) Steady state conditions, b) Axisymmetry, c) A velocity field given by (π=0, θ=θ(r), Z=0) for the interstellar gas (where π,θ and Z are the radial, azimuthal and vertical to the galactic plane components and r is the distance from the galactic center). Then, the direction of magnetic field must be azimuthal and the plasma distribution is compatible with ring structures.

scholarly journals Galaxy spin direction distribution in HST and SDSS show similar large-scale asymmetry

2020 ◽  
Vol 37 ◽  
Author(s):  
Lior Shamir
Keyword(s):  
Large Scale ◽  
Spiral Galaxies ◽  
Hubble Space Telescope ◽  
Gravitational Interaction ◽  
Large Data ◽  
Sloan Digital Sky Survey ◽  
Data Sets ◽  
Dipole Axis ◽  
Data Set ◽  
The Asymmetry

Abstract Several recent observations using large data sets of galaxies showed non-random distribution of the spin directions of spiral galaxies, even when the galaxies are too far from each other to have gravitational interaction. Here, a data set of $\sim8.7\cdot10^3$ spiral galaxies imaged by Hubble Space Telescope (HST) is used to test and profile a possible asymmetry between galaxy spin directions. The asymmetry between galaxies with opposite spin directions is compared to the asymmetry of galaxies from the Sloan Digital Sky Survey. The two data sets contain different galaxies at different redshift ranges, and each data set was annotated using a different annotation method. The results show that both data sets show a similar asymmetry in the COSMOS field, which is covered by both telescopes. Fitting the asymmetry of the galaxies to cosine dependence shows a dipole axis with probabilities of $\sim2.8\sigma$ and $\sim7.38\sigma$ in HST and SDSS, respectively. The most likely dipole axis identified in the HST galaxies is at $(\alpha=78^{\rm o},\delta=47^{\rm o})$ and is well within the $1\sigma$ error range compared to the location of the most likely dipole axis in the SDSS galaxies with $z>0.15$ , identified at $(\alpha=71^{\rm o},\delta=61^{\rm o})$ .

The entrainment interface

1972 ◽  
Vol 51 (1) ◽  
pp. 97-118 ◽  
Author(s):  
O. M. Phillips
Keyword(s):  
Velocity Field ◽  
Turbulent Flow ◽  
Surface Area ◽  
Large Scale ◽  
Positive Curvature ◽  
Lagrangian Description ◽  
Eulerian Description ◽  
Entrainment Process ◽  
Necessary And Sufficient ◽  
Small Disturbances

A theory is developed to describe the evolution of the entrainment interface in turbulent flow, in which the surface is convoluted by the large-scale eddies of the motion and at the same time advances relative to the fluid as a result of the micro-scale entrainment process. A pseudo-Lagrangian description of the process indicates that the interface is characterized by the appearance of ‘billows’ of negative curvature, over which surface area is, on average, being generated, separated by re-entrant wedges (lines of very large positive curvature) where surface area is consumed. An alternative Eulerian description allows calculation of the development of the interfacial configuration when the velocity field is prescribed. Several examples are considered in which the prescribed velocity field in the z direction is of the general form w = Wf(x – Ut), where the maximum value of the function f is unity. These indicate the importance of leading points on the surface which are such that small disturbances in the vicinity will move away from the point in all directions. The necessary and sufficient condition for the existence of one or more leading points on the surface is that U [les ] V, the speed of advance of an element of the surface relative to the fluid element at the same point. The existence of leading points is accompanied by the appearance of line discontinuities in the surface slope re-entrant wedges, In these circumstances, the overall speed of advance of the convoluted surface is found to be W + (V2 – U2)½, where W is the maximum outwards velocity in the region; this result is independent of the distribution f.When the speed U with which an ‘eddy’ moves relative to the outside fluid is greater than the speed of advance V of an element of the front, the interface develops neither leading points nor discontinuities in slope; the amplitude of the surface convolutions and the overall entrainment speed are both reduced greatly. In a turbulent flow, therefore, the large-scale motions influencing entrainment are primarily those that move slowly relative to the outside fluid (with relative speed less than V). The experimental results of Kovasznay, Kibens & Blackwelder (1970) are reviewed in the light of these conclusions. It appears that in their experiments the entrainment speed V is of the order fifteen times the Kolmogorov velocity, the large constant of proportionality being apparently the result of augmentation by micro-convolutions of the interface associated with small and meso-scale eddies of the turbulence.

Buoyancy effects on large-scale motions in convective atmospheric boundary layers: implications for modulation of near-wall processes

2018 ◽  
Vol 856 ◽  
pp. 135-168 ◽  
Author(s):  
S. T. Salesky ◽  
W. Anderson
Keyword(s):  
Boundary Layer ◽  
Velocity Field ◽  
Boundary Layers ◽  
Vertical Velocity ◽  
Amplitude Modulation ◽  
Large Scale ◽  
Streamwise Velocity ◽  
Small Scale ◽  
Convective Conditions ◽  
Wide Range

A number of recent studies have demonstrated the existence of so-called large- and very-large-scale motions (LSM, VLSM) that occur in the logarithmic region of inertia-dominated wall-bounded turbulent flows. These regions exhibit significant streamwise coherence, and have been shown to modulate the amplitude and frequency of small-scale inner-layer fluctuations in smooth-wall turbulent boundary layers. In contrast, the extent to which analogous modulation occurs in inertia-dominated flows subjected to convective thermal stratification (low Richardson number) and Coriolis forcing (low Rossby number), has not been considered. And yet, these parameter values encompass a wide range of important environmental flows. In this article, we present evidence of amplitude modulation (AM) phenomena in the unstably stratified (i.e. convective) atmospheric boundary layer, and link changes in AM to changes in the topology of coherent structures with increasing instability. We perform a suite of large eddy simulations spanning weakly ($-z_{i}/L=3.1$) to highly convective ($-z_{i}/L=1082$) conditions (where$-z_{i}/L$is the bulk stability parameter formed from the boundary-layer depth$z_{i}$and the Obukhov length $L$) to investigate how AM is affected by buoyancy. Results demonstrate that as unstable stratification increases, the inclination angle of surface layer structures (as determined from the two-point correlation of streamwise velocity) increases from$\unicode[STIX]{x1D6FE}\approx 15^{\circ }$for weakly convective conditions to nearly vertical for highly convective conditions. As$-z_{i}/L$increases, LSMs in the streamwise velocity field transition from long, linear updrafts (or horizontal convective rolls) to open cellular patterns, analogous to turbulent Rayleigh–Bénard convection. These changes in the instantaneous velocity field are accompanied by a shift in the outer peak in the streamwise and vertical velocity spectra to smaller dimensionless wavelengths until the energy is concentrated at a single peak. The decoupling procedure proposed by Mathiset al.(J. Fluid Mech., vol. 628, 2009a, pp. 311–337) is used to investigate the extent to which amplitude modulation of small-scale turbulence occurs due to large-scale streamwise and vertical velocity fluctuations. As the spatial attributes of flow structures change from streamwise to vertically dominated, modulation by the large-scale streamwise velocity decreases monotonically. However, the modulating influence of the large-scale vertical velocity remains significant across the stability range considered. We report, finally, that amplitude modulation correlations are insensitive to the computational mesh resolution for flows forced by shear, buoyancy and Coriolis accelerations.

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