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 Structural and Kinematic Properties of Populations of the Andromeda Galaxy

1972 ◽  
Vol 44 ◽  
pp. 37-45 ◽  
Author(s):  
J. Einasto
Keyword(s):  
Mass Distribution ◽  
Globular Clusters ◽  
Velocity Dispersion ◽  
Strong Dependence ◽  
Stellar Content ◽  
Distribution Models ◽  
Model Calculations ◽  
The Galaxy ◽  
Spectrophotometric Data ◽  
Virial Mass

New observational data (Spinrad, 1970; Van den Bergh, 1970; Rubin and Ford, 1970) are used to determine structural and kinematic parameters of the nucleus, the subsystem of globular clusters, and interstellar hydrogen in M31.The mass derived for the nucleus from the new spectrophotometric data is in good agreement with the virial mass 6 × 108M⊙. Model calculations show that there is no appreciable exchange of stars between the nucleus and the bulge. The rotation energy of the nucleus is only 7.5% of the total kinetic energy; the central density is 2 × 106M⊙ pc−3.The mean radius of the subsystem of globular clusters is 4.5 kpc. This indicates that the subsystem of old stars is not identical with the spheroidal component of the galaxy, whose mean radius is only 1 kpc. Radial velocity dispersion of globular clusters is only half of that of the nucleus. This shows a strong dependence of the velocity dispersion on distance to the center of the galaxy and a bias in mass determination of a galaxy from velocity dispersion near the nucleus.On the basis of data on rotation two mass distribution models have been found, differing from each other in respect of the mass concentration to the center. Spectrophotometric data on the stellar content of the bulge are urgently needed to solve the mass distribution problem.

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 Can We Measure H0 with VLBI Observations of Gravitational Images?

1988 ◽  
Vol 129 ◽  
pp. 207-208
Author(s):  
E. E. Falco ◽  
M. V. Gorenstein ◽  
I. I. Shapiro
Keyword(s):  
Time Delay ◽  
Mass Distribution ◽  
Velocity Dispersion ◽  
Gravitational Lens ◽  
Lens System ◽  
Relative Time ◽  
Surface Mass ◽  
A Value ◽  
Vlbi Observations ◽  
The Difference

We have used the relative positions and magnifications of the A and B images in the gravitational lens system 0957+561, obtained from VLBI observations, to constrain a model for the surface mass distribution of the lens. With measurements of the difference ΔτBA in propagation times associated with A and B (the “relative time delay”) and of the velocity dispersion of the main lensing galaxy, both to be obtained, our model will yield a value for H0 with an uncertainty of ∼ 20% due mainly to uncertainties in our assumptions.

scholarly journals About the Coma Cluster (Progress Report)

1987 ◽  
Vol 117 ◽  
pp. 112-112
Author(s):  
D. Gerbal ◽  
G. Mathez ◽  
A. Mazure ◽  
E. Salvadore-Solé
Keyword(s):  
Total Mass ◽  
Velocity Dispersion ◽  
Dynamical Evolution ◽  
Dynamical Analysis ◽  
Radial Dependence ◽  
Cluster Center ◽  
Coma Cluster ◽  
Massive Galaxies ◽  
Relaxation Effects ◽  
The Galaxy

The study of the dynamics of the Coma Cluster is of interest for several reasons. First, there exists a great deal of observational information about the cluster, including data on morphology, magnitude, color and redshift for the galaxies, and reasonably detailed x-ray data for the hot gas. Second, the present dynamical state of the cluster is reasonably well-defined. In addition, the segregation of the more luminous (≡ massive) galaxies towards the cluster center shows that two-body relaxation effects are well-advanced (Capelato et al. 1980). The profile of velocity dispersion with radius shows that in the outer parts of the cluster the galaxy velocities are non-isothermal (des Forêts et al. 1984). There is, however, evidence of continuing dynamical evolution. The velocity field of the galaxies at large distances from the center of the cluster suggests continuing infall (Capelato et al. 1982), and two sub-condensations are located in the inner regions (Mazure and Proust 1986). A new dynamical analysis for the cluster is being carried out in two stages. First, a relaxed model with a wide mass spectrum (c.f. Inagaki 1980) is fitted to the data. The contribution of the intergalactic gas is taken into account. With HO = 75 km/sec/Mpc, the total mass within a 3° radius of the center is ∼ 1.5 × 1015 M⊙, of which ∼ 30% is in the intergalactic medium, and M/L ∼ 75 M⊙/L⊙. The ratio of specific energies of the galaxies and the gas is ∼ 1.1, i.e., there is no scale-height problem (these results are described more fully by Gerbal et al. 1986). A second “model independent” analysis using the profiles of the galactic density and velocity dispersion gives the radial dependence of the galactic mass, the gas mass and also gives the total mass, which is found to be ∼ 1.1 × 1015 M⊙ within 3° (Gerbal et al. 1984).

Identification of the Velocity, Thickness, and Interfacial Roughness of Coating Using Full Time-Domain URCPS: Cross-Correlation-Based Inverse Problem

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Zhiyuan Ma ◽  
Li Lin ◽  
Shijie Jin ◽  
Mingkai Lei
Keyword(s):  
Time Domain ◽  
Measurement Errors ◽  
Cross Correlation ◽  
Inversion Method ◽  
Full Time ◽  
Interfacial Roughness ◽  
Measured Velocity ◽  
Detection Frequency ◽  
Relative Errors ◽  
Good Agreement

Aiming at characterizing interfacial roughness of thin coatings with unknown sound velocity and thickness, we derive a full time-domain ultrasonic reflection coefficient phase spectrum (URCPS) as a function of interfacial roughness based on the phase screen approximation theory. The constructed URCPS is used to determine the velocity, thickness, and interfacial roughness of specimens through the cross-correlation algorithm. The effect of detection frequency on the roughness measurement is investigated through the finite element method. A series of simulations were implemented on Ni-coating specimens with a thickness of 400 μm and interfacial roughness of 1.9–39.8 μm. Simulation results indicated that the measurement errors of interfacial roughness were less than 10% when the roughness satisfies the relationship of Rq = 1.6–10.0%λ. The measured velocity and thicknesses were in good agreement with those imported in simulation models with less than 9.3% error. Ultrasonic experiments were carried out on two Ni-coating specimens through a flat transducer with an optimized frequency of 15 MHz. Compared with the velocities measured by time-of-flight (TOF) method, the relative errors of inversed velocities were all less than 10%. The inversed thicknesses were in good agreement with those observed by optical microscopy with less than 10.9% and 7.6% error. The averaged interfacial roughness determined by the ultrasonic inversion method was 16.9 μm and 30.7 μm, respectively. The relative errors were 5.1% and 2.0% between ultrasonic and confocal laser scanning microscope (CLSM) method, respectively.

scholarly journals No evidence for intermediate-mass black holes in the globular clusters ω Cen and NGC 6624

2019 ◽  
Vol 488 (4) ◽  
pp. 5340-5351 ◽  
Author(s):  
H Baumgardt ◽  
C He ◽  
S M Sweet ◽  
M Drinkwater ◽  
A Sollima ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Globular Clusters ◽  
Surface Brightness ◽  
Velocity Dispersion ◽  
Stellar Mass ◽  
Main Sequence Stars ◽  
Intermediate Mass ◽  
Measured Velocity ◽  
Large Grid

ABSTRACT We compare the results of a large grid of N-body simulations with the surface brightness and velocity dispersion profiles of the globular clusters ω Cen and NGC 6624. Our models include clusters with varying stellar-mass black hole retention fractions and varying masses of a central intermediate-mass black hole (IMBH). We find that an $\sim 45\, 000$ M⊙ IMBH, whose presence has been suggested based on the measured velocity dispersion profile of ω Cen, predicts the existence of about 20 fast-moving, m > 0.5 M⊙, main-sequence stars with a (1D) velocity v > 60 km s−1 in the central 20 arcsec of ω Cen. However, no such star is present in the HST/ACS proper motion catalogue of Bellini et al. (2017), strongly ruling out the presence of a massive IMBH in the core of ω Cen. Instead, we find that all available data can be fitted by a model that contains 4.6 per cent of the mass of ω Cen in a centrally concentrated cluster of stellar-mass black holes. We show that this mass fraction in stellar-mass BHs is compatible with the predictions of stellar evolution models of massive stars. We also compare our grid of N-body simulations with NGC 6624, a cluster recently claimed to harbour a 20 000 M⊙ black hole based on timing observations of millisecond pulsars. However, we find that models with MIMBH > 1000 M⊙ IMBHs are incompatible with the observed velocity dispersion and surface brightness profile of NGC 6624, ruling out the presence of a massive IMBH in this cluster. Models without an IMBH provide again an excellent fit to NGC 6624.

scholarly journals The Dark Halo – Spheroid Conspiracy

2012 ◽  
Vol 8 (S295) ◽  
pp. 208-208
Author(s):  
Rhea-Silvia Remus ◽  
Andreas Burkert ◽  
Klaus Dolag ◽  
Peter H. Johansson ◽  
Thorsten Naab ◽  
...  
Keyword(s):  
Elliptical Galaxies ◽  
Total Density ◽  
Dark Halo ◽  
Coma Cluster ◽  
Density Profiles ◽  
Stellar Component ◽  
Strong Lensing ◽  
The Galaxy ◽  
Good Agreement

AbstractObservational results from strong lensing and dynamical modeling indicate that the total density profiles of early-type galaxies are close to isothermal, i.e. ρtot ∝ rγ with γ ≈ −2. To understand the origin of this universal slope we study a set of simulated spheroids formed in cosmological hydrodynamical zoom-in simulations (see Oser et al. 2010 for more details). We find that the total stellar plus dark matter density profiles of all our simulations on average can be described by a power law with a slope of γ ≈ −2.1, with a tendency towards steeper slopes for more compact, lower mass ellipticals, while the total intrinsic velocity dispersion is flat for all simulations, independent of the values of γ. Our results are in good agreement with observations of Coma cluster ellipticals (Thomas et al. 2007) and results from strong lensing (Sonnenfeld et al. 2012). We find that for z ≳ 2 the majority of the stellar build-up occurs through in-situ star formation, i.e. the gas falls to the center of the galaxy and forms stars, causing the galaxy to be more compact and thus the stellar component to be more dominant. As a result, the total density slopes at z ≈ 2 are generally steeper (around γ ≈ −3). Between z = 2 and z = 0 galaxies grow mostly through dry merging, with each merging event shifting the slope more towards γ ≈ −2. We conclude from our simulations that the steepness of the slope of present day galaxies is a signature of the importance of mostly dry mergers in the formation of an elliptical, and suggest that all elliptical galaxies will with time end up in a configuration with a density slope of γ ≈ −2. For a more detailed analysis with a larger sample of simulations see Remus et al. (2013).

scholarly journals The Masses of Quasars and AGN: Correlating the Accretion-Disk and the Emission-Line Methods

1989 ◽  
Vol 134 ◽  
pp. 62-64
Author(s):  
Amri Wandel
Keyword(s):  
Emission Line ◽  
Accretion Disk ◽  
Velocity Dispersion ◽  
Accretion Rate ◽  
Compact Object ◽  
Black Hole Mass ◽  
Uv Spectrum ◽  
Highly Correlated ◽  
The Masses ◽  
Good Agreement

The UV continuum spectrum is used to extract the mass (and accretion rate) of quasars and AGN, assuming the UV is dominated by the emission from a thin accretion disk. This is done by fitting the observed luminosity and spectral slope in the UV by an accretion disk mode, giving the accretion parameters (black hole mass and accretion rate). An independent estimate of the mass is obtained using the emission-line method, which assumes that the velocity dispersion of the broad emission-line s is induced by the gravitational potential of the central compact object. For a sample of 36 quasars and Seyfert 1 galaxies, for which both data, the UV spectrum and the Hβ line width are available, the masses calculated with the two independent methods are in good agreement (within a factor of 2 for 75% of the sample) and highly correlated. Over three orders of magnitude in luminosity, the mass is found to increase less than linearely with luminosity, being in the range 108 < M < 1010M⊙, with L(1450A)/LEdd ranging from 0.001 for Seyferts to 0.03 for bright quasars.

scholarly journals The X-Ray Emitting Galaxy Group SHKH 360

1996 ◽  
Vol 171 ◽  
pp. 453-453
Author(s):  
H. Tiersch ◽  
H. Oleak ◽  
D. Stoll ◽  
A.D. Schwope ◽  
S. Neizvestny ◽  
...  
Keyword(s):  
Velocity Dispersion ◽  
Red Shift ◽  
Space Density ◽  
X Ray ◽  
Strongly Interacting ◽  
Crossing Time ◽  
Virial Mass ◽  
Image Position

Shkh 360 has the characteristic signature of a strongly interacting group. Seven galaxies are embedded in a common extended halo and the isophotes indicate clear signs of alignment in B,V, and R. The parameters of the group as the red shift, z, the distance, d, the projected diameter, D, (basing on H = 55 km/s/Mpc), the virial radius, Rvir, the velocity dispersion, σv, the virial mass, the crossing time, τ, and the space density of galaxies, n, are given in the Table.

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