scholarly journals Properties of E & S0 Galaxies in the Coma Cluster

1996 ◽  
Vol 171 ◽  
pp. 419-419
Author(s):  
Dörte Mehlert ◽  
Ralf Bender ◽  
Roberto Saglia ◽  
Gary Wegner ◽  
Inger Jørgensen
Keyword(s):  
Kinetic Energy ◽  
Stellar Population ◽  
Velocity Dispersion ◽  
Low Density ◽  
Coma Cluster ◽  
Measured Velocity ◽  
The Mean ◽  
Velocity Dispersions ◽  
S0 Galaxies ◽  
Mean Kinetic Energy

As one of the richest nearby clusters, Coma is the ideal place to study the structure of galaxies as a function of environmental density, thus to constrain the theories of galaxy formation and evolution. For a magnitude limited sample of ≈ 40 E and S0 galaxies we want to obtain spectra with sufficient S/N and spatial resolution, that we can derive the rotation curves, the velocity dispersions profiles and the radial gradients of the line indices of Mg, Fe and Hβ. Following questions will be addressed: •Are the radial velocity dispersion profiles and the rotation of galaxies in high density environments similar to those in low density environments? Data for galaxies in low density environment are available from Bender et al. (1994, MNRAS, 269, 785). Are the centrally measured velocity dispersions representative for the mean kinetic energy of the galaxy?•Can the scatter in the Fundamental Plane (FP) - which tightly correlates the radii, surface brightnesses and (central) velocity dispersions (Djorgovski & Davis, 1987, ApJ, 313, 59; Dressier et al. 1987, ApJ, 313, 42) - for the Coma cluster be reduced if the mean kinetic energy is used instead of the central velocity dispersion? Can we derive stronger constraint on the variations in the M/L ratio than already implied by the FP?•The radial gradients of the line indices can be used to test the hypothesis that the metallicity gradient depends on the so-called “escape velocity” of the stars introduced by Franx & Illingworth (1990, ApJ, 359, L41). Also we can check whether the age of the stellar population varies with radius. Ages and metallicities can be estimated from the data with the use of stellar population models (Worthey 1994, ApJS, 95, 105; Bruzual & Chariot 1993, ApJ, 405, 538).•How does the radial variation of stellar populations and kinematics within the galaxies vary as a function of the clusters density profile?

scholarly journals Line-Strength Profiles in Early-Type Galaxies

1995 ◽  
Vol 164 ◽  
pp. 453-453
Author(s):  
David Fisher ◽  
Garth Illingworth ◽  
Marijn Franx
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Line Strength ◽  
Strong Correlations ◽  
Metal Line ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
The Mean ◽  
S0 Galaxies ◽  
Line Strengths

Line-strengths and their gradients in Mg, Fe, and Hβ have been determined for a sample of 9 brightest cluster (BCG), 7 elliptical, and 15 S0 galaxies in order to study their stellar populations and investigate their relationship to one another. We find that BCGs follow the same relationship between central Mgb line-strength and central velocity dispersion found for ellipticals while the S0 galaxies show significant scatter with respect to this relation. Brightest cluster galaxies are in agreement with the known trend towards more massive ellipticals having larger [Mg/Fe] ratios while the internal gradients within our BCG and E galaxies are consistent with a roughly constant [Mg/Fe] ratio. We find that a correlation exists between the central [Mg/Fe] ratio and average Hβ line-strength in the sense that BCG and E galaxies with larger [Mg/Fe] ratios have lower Hβ strengths. For our BCG and E galaxies, Hβ is the best predictor of [Mg/Fe] ratio. The Mgb metallicity gradients for BCGs and ellipticals are similar and consistent with a reduction in the mean metallicity of the stellar population by about a factor of 2 over a factor of ten in radius. No strong correlations are found between the metallicity gradient sizes and either kinematic or line-strength parameters of the E and BCG galaxies. The S0 disks display roughly constant Mg, Fe, and Hβ line-strengths with radius indicating that they have uniform age and metallicity throughout. S0 galaxy minor axes ‘bulge’ metal line-strength gradients are similar to elliptical gradients and fall to values lower than those found in the disks.

Study of the Mechanisms of Vortex Variability in the Lofoten Basin Based on the Energy Analysis

2021 ◽  
Vol 37 (3) ◽  
Author(s):  
V. S. Travkin ◽  
◽  
T. V. Belonenko ◽  
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Baroclinic Instability ◽  
Positive Trend ◽  
Barotropic Instability ◽  
Available Potential Energy ◽  
Conversion Rates ◽  
Order Of Magnitude ◽  
The Mean ◽  
Mean Kinetic Energy

Purpose. The Lofoten Basin is one of the most energetic zones of the World Ocean characterized by high activity of mesoscale eddies. The study is aimed at analyzing different components of general energy in the basin, namely the mean kinetic and vortex kinetic energy calculated using the integral of the volume of available potential and kinetic energy of the Lofoten Vortex, as well as variability of these characteristics. Methods and Results. GLORYS12V1 reanalysis data for the period 2010–2018 were used. The mean kinetic energy and the eddy kinetic one were analyzed; and as for the Lofoten Vortex, its volume available potential and kinetic energy were studied. The mesoscale activity of eddies in winter is higher than in summer. Evolution of the available potential energy and kinetic energy of the Lofoten Vortex up to the 1000 m horizon was studied. It is shown that the vortex available potential energy exceeds the kinetic one by an order of magnitude, and there is a positive trend with the coefficient 0,23⋅1015 J/year. It was found that in the Lofoten Basin, the intermediate layer from 600 to 900 m made the largest contribution to the potential energy, whereas the 0–400 m layer – to kinetic energy. The conversion rates of the mean kinetic energy into the vortex kinetic one and the mean available potential energy into the vortex available potential one (barotropic and baroclinic instability) were analyzed. It is shown that the first type of transformation dominates in summer, while the second one is characterized by its increase in winter. Conclusions. The vertical profile shows that the kinetic energy of eddies in winter is higher than in summer. The available potential energy of a vortex is by an order of magnitude greater than the kinetic energy. An increase in the available potential energy is confirmed by a significant positive trend and by a decrease in the vortex Burger number. The graphs of the barotropic instability conversion rate demonstrate the multidirectional flows in the vortex zone with the dipole structure observed in a winter period, and the tripole one – in summer. The barotropic instability highest intensity is observed in summer. The baroclinic instability is characterized by intensification of the regime in winter that is associated with weakening of stratification in this period owing to winter convection.

Different Laws of Increasing of Stellar Dispersion: Observational Flaws or Natural Property of Stellar Population?

1996 ◽  
Vol 169 ◽  
pp. 433-434
Author(s):  
A.M. Fridman ◽  
O.V. Khoruzhii ◽  
A.E. Piskunov
Keyword(s):  
Critical Analysis ◽  
Stellar Population ◽  
Velocity Dispersion ◽  
Power Laws ◽  
Dispersion Relations ◽  
Solar Neighborhood ◽  
Natural Property ◽  
Stellar Component ◽  
Velocity Dispersions

Observations show that in the solar neighborhood the velocity dispersions of disk stars increase with their age. In this work we present the results of a critical analysis of the existing interpretations of the data, as well as of previous theoretical explanations of the heating phenomenon. It is shown that different relaxation mechanisms based on star-cloud collisions can result in a wide set of age–velocity dispersion relations (AVDR). Thus the observed differing power laws of the heating of the stellar component can be a consequence of the different relaxation mechanisms.

scholarly journals The Galactic Neighbourhood

1978 ◽  
Vol 79 ◽  
pp. 71-91 ◽  
Author(s):  
G. A. Tammann ◽  
R. Kraan
Keyword(s):  
Luminosity Function ◽  
Velocity Dispersion ◽  
Radial Component ◽  
Virgo Cluster ◽  
Cluster Centre ◽  
Different Types ◽  
Peculiar Motion ◽  
The Mean ◽  
S0 Galaxies ◽  
Hubble Flow

Several properties of the 131 galaxies known within 9. 1 Mpc are investigated. 88 of these galaxies are concentrated into eight groups, leaving 33 percent of true field galaxies. There are E/S0 and S0 galaxies among the field galaxies; their types must be of cosmogonic origin. the groups have small velocity dispersion which limits the mean mass-to-light ratio for the different types of group galaxies to m/L < 20. Within the supergalactic plane the deviation from an ideal Hubble flow are small: the changes of ΔHO/<HO> with distance and direction are not larger than ten percent; the radial component of the peculiar motion of field galaxies is <25 km s−1. the differential luminosity function of S/Im galaxies is well approximated by a Gaussian with and . the luminosity function of E/S0 galaxies is much flatter with a possible minimum, separating true E's and dwarf ellipticals (Reaves, 1977). the sample galaxies are strongly concentrated toward the supergalactic plane; at a distance of 4 Mpc of the plane the luminosity density drops to half its value. There is also a pronounced luminosity density decrease with increasing distance from the Virgo cluster centre; at a distance of 30 Mpc the density has decreased by more than a factor of 104. the best estimate of the mean luminosity density within a sphere of 30 Mpc radius centered on the Virgo cluster is 1.5 · 108 L⊙ Mpc−3.

Dependence of the mean kinetic energy of fragments on the fissionable nucleus mass

1963 ◽  
Vol 15 (5) ◽  
pp. 1177-1178 ◽  
Author(s):  
V. N. Okolovich ◽  
V. I. Bol'shov ◽  
L. D. Gordeeva ◽  
G. N. Smirenkin
Keyword(s):  
Kinetic Energy ◽  
Nucleus Mass ◽  
The Mean ◽  
Fissionable Nucleus ◽  
Mean Kinetic Energy

Seasonal Variability of Mesoscale Instabilities in the Azores Current System

2020 ◽  
Author(s):  
João Bettencourt ◽  
Carlos Guedes Soares
Keyword(s):  
Kinetic Energy ◽  
Reynolds Stress ◽  
North Atlantic ◽  
Current System ◽  
Baroclinic Instability ◽  
Primitive Equation ◽  
The Mean ◽  
Eastern North Atlantic ◽  
Jet Axis ◽  
Mean Kinetic Energy

&lt;p&gt;The Azores Current-Front system coincides with the northern limit of the subtropical gyre in&amp;#160; the Eastern North Atlantic. The mean zonal jet is positioned south of the Azores archipelago&amp;#160; and extends from west of the mid-atlantic ridge to the Gulf of Cadiz, where it partially&amp;#160; turns south. North of the main jet, a sub-surface counter-current is found, flowing westwards. The associated thermal front separates the warm subtropical waters from the colder subpolar waters. The instantaneous flow in the Azores Current/Front system is characterized by the presence of meandering currents with length scales of 200 km that regularly shed anticyclonic warm water and cyclonic cold water eddies to the north and south of the mean jet axis, respectively, due to vortex stretching and the planetary beta effect. The time scale of eddy shedding is 100-200 days. On the meandering arms of the current, downwelling&amp;#160;&lt;br&gt;and upwelling cells are found and sharp thermal gradients are formed and a residual poleward heat transport is observed. The instability cycle that originates the mesoscale meanders and the eddies is well-known from quasi-geostrophic and primitive equation models initialized from a basic baroclinic state: a first phase of baroclinic instability feeds on available potential energy to raise eddy kinetic energy levels, that, in a second phase feed the mean kinetic energy by Reynolds stress convergence. The cycle repeats itself as long as the APE reservoir is filled at the end of each cycle.&lt;/p&gt;&lt;p&gt;However, seasonal variability of the zonal jet dynamics has not been addressed before and it can provide valuable insights in to the variations of the Eastern North Atlantic between the subtropical and subpolar gyres. We use a primitive equation regional ocean model of the Eastern Central North Atlantic with realistic climatological wind and thermal forcing to study the yearly cycle of meandering, eddy shedding and restoration of the mean jet in the Azores/Current system. We observe an semi-annual cycle in the jet's kinetic energy with maxima in Summer/Winter and minima in early Spring/Autumn. Potential energy conversion by baroclinic instability occurs throughout the year but is predominant in the first half of the year. The mean kinetic energy draws from the turbulent kinetic energy through Reynolds stress convergence in periods of 50 - 100 days, that are followed by short barotropic instability periods. During Winter, Reynolds stress convergence, and thus mean jet reinforcement from the mesoscale eddy field, occurs along the jet meridional extent, in the top 500 m of the water column, but from Spring to Autumn it is observed only in the southern flank of the mean jet axis.&lt;/p&gt;

scholarly journals Induced energy polarization of the vacuum and the Coma cluster

2013 ◽  
Vol 91 (12) ◽  
pp. 1114-1120 ◽  
Author(s):  
A. Raymond Penner
Keyword(s):  
Mass Distribution ◽  
Velocity Dispersion ◽  
Hydrostatic Equilibrium ◽  
Coma Cluster ◽  
Measured Velocity ◽  
Virial Mass ◽  
Intracluster Gas ◽  
Good Agreement

The theory of an induced energy polarized vacuum is applied to the Coma cluster. The theoretical virial mass distribution of the cluster is determined and found to be in good agreement with previous virial mass estimates. A more concentrated intracluster gas profile than one based on the assumption that the gas is in hydrostatic equilibrium and isothermal does, however, lead to better agreement with measured shear values in the inner regions. The theory also leads to good agreement with measured velocity dispersion values in the case of the galaxies of the cluster being in radial orbits.

scholarly journals How Does the Vertical Profile of Baroclinicity Affect the Wave Instability?

2011 ◽  
Vol 68 (4) ◽  
pp. 863-877 ◽  
Author(s):  
Toshiki Iwasaki ◽  
Chihiro Kodama
Keyword(s):  
Growth Rate ◽  
Kinetic Energy ◽  
Wave Energy ◽  
Vertical Profile ◽  
Baroclinic Instability ◽  
Zonal Flow ◽  
Instability Waves ◽  
P Flux ◽  
The Mean ◽  
Mean Kinetic Energy

Abstract The growth rate of baroclinic instability waves is generalized in terms of wave–mean flow interactions, with an emphasis on the influence of the vertical profile of baroclinicity. The wave energy is converted from the zonal mean kinetic energy and the growth rate is proportional to the mean zonal flow difference between the Eliassen–Palm (E-P) flux convergence and divergence areas. Mass-weighted isentropic zonal means facilitate the expression of the lower boundary conditions for the mass streamfunctions and E-P flux. For Eady waves, intersections of isentropes with lower/upper boundaries induce the E-P flux divergence/convergence. The growth rate is proportional to the mean zonal flow difference between the two boundaries, indicating that baroclinicity at each level contributes evenly to the instability. The reduced zonal mean kinetic energy is compensated by a conversion from the zonal mean available potential energy. Aquaplanet experiments are carried out to investigate the actual characteristics of baroclinic instability waves. The wave activity is shown to be sensitive to the upper-tropospheric baroclinicity, though it may be most sensitive to baroclinicity near 800 hPa, which is the maximal level of the E-P flux. The local wave energy generation rate suggests that the increased upper-tropospheric zonal flow directly enhances the upper-tropospheric wave energy at the midlatitudes. Note that the actual baroclinic instability waves accompany a considerable amount of the equatorward E-P flux, which causes extinction of wave energy in the subtropical upper troposphere.

On the mean kinetic energy of the proton in strong hydrogen bonded systems

2016 ◽  
Vol 144 (5) ◽  
pp. 054302 ◽  
Author(s):  
Y. Finkelstein ◽  
R. Moreh ◽  
S. L. Shang ◽  
Ya. Shchur ◽  
Y. Wang ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
The Mean ◽  
Hydrogen Bonded Systems ◽  
Mean Kinetic Energy ◽  
Hydrogen Bonded

Energetics of the Climate System

2019 ◽  
Author(s):  
Jin-Song von Storch
Keyword(s):  
Kinetic Energy ◽  
General Circulation ◽  
General Circulation Models ◽  
Eddy Kinetic Energy ◽  
Energy Cycle ◽  
Lorenz Energy Cycle ◽  
The Mean ◽  
Realistic Data ◽  
Mean Kinetic Energy ◽  
Energy Pathways

The energetics considerations based on Lorenz’s available potential energy A focus on identification and quantification of processes capable of converting external energy sources into the kinetic energy of atmospheric and oceanic general circulations. Generally, these considerations consist of: (a) identifying the relevant energy compartments from which energy can be converted against friction to kinetic energy of motions of interests; (b) formulating for these energy compartments budget equations that describe all possible energy pathways; and (c) identifying the dominant energy pathways using realistic data. In order to obtain a more detailed description of energy pathways, a partitioning of motions, for example, into a “mean” and an “eddy” component, or into a diabatic and an adiabatic component, is used. Since the budget equations do not always suggest the relative importance of all possible pathways, often not even the directions, data that describe the atmospheric and the oceanic state in a sufficiently accurate manner are needed for evaluating the energy pathways. Apart from the complication due to different expressions of A, ranging from the original definition by Lorenz in 1955 to its approximations and to more generally defined forms, one has to balance the complexity of the respective budget equations that allows the evaluation of more possible energy pathways, with the quality of data available that allows sufficiently accurate estimates of energy pathways. With regard to the atmosphere, our knowledge, as inferred from the four-box Lorenz energy cycle, has consolidated in the last two decades, by, among other means, using data assimilation products obtained by combining observations with realistic atmospheric general circulation models (AGCMs). The eddy kinetic energy, amounting to slightly less than 50% of the total kinetic energy, is supported against friction through a baroclinic pathway “fueled” by the latitudinally dependent diabatic heating. The mean kinetic energy is supported against friction by converting eddy kinetic energy via inverse cascades. For the ocean, our knowledge is still emerging. The description through the four-box Lorenz energy cycle is approximative and was only estimated from a simulation of a 0.1° oceanic general circulation models (OGCM) realistically forced at the sea surface, rather than from a data assimilation product. The estimates obtained so far suggest that the oceanic eddy kinetic energy, amounting almost 75% of the total oceanic kinetic energy, is supported against friction through a baroclinic pathway similar to that in the atmosphere. However, the oceanic baroclinic pathway is “fueled” to a considerable extent by converting mean kinetic energy supported by winds into mean available potential energy. Winds are also the direct source of the kinetic energy of the mean circulation, without involving noticeable inverse cascades from transients, at least not for the ocean as a whole. The energetics of oceanic general circulation can also be examined by separating diabatic from adiabatic processes. Such a consideration is thought to be more appropriate for understanding the energetics of the oceanic meridional overturning circulation (MOC), since this circulation is sensitive to density changes induced by diabatic mixing. Further work is needed to quantify the respective energy pathways using realistic data.

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