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Articles 31 - 34 of 34
Full-Text Articles in Cosmology, Relativity, and Gravity
Large-Scale Power Spectrum And Structures From The Enear Galaxy Peculiar Velocity Catalogue, S. Zaroubi, M. Bernardi, L. N. Da Costa, Y. Hoffman, M. V. Alonso, G. Wegner
Large-Scale Power Spectrum And Structures From The Enear Galaxy Peculiar Velocity Catalogue, S. Zaroubi, M. Bernardi, L. N. Da Costa, Y. Hoffman, M. V. Alonso, G. Wegner
Dartmouth Scholarship
We estimate the mass density fluctuations power spectrum (PS) on large scales by applying a maximum likelihood technique to the peculiar velocity data of the recently completed redshift—distance survey of early-type galaxies (hereafter ENEAR). Parametric cold dark matter (CDM)-like models for the PS are assumed, and the best-fitting parameters are determined by maximizing the probability of the model given the measured peculiar velocities of the galaxies, their distances and estimated errors. The method has been applied to CDM models with and without COBE normalization. The general results are in agreement with the high-amplitude power spectra found from similar analyses of …
A Spectroscopic Redshift For The Cl 0024+16 Multiple Arc System: Implications For The Central Mass Distribution, Tom Broadhurst, Xiaosheng Huang, Brenda Frye, Richard Ellis
A Spectroscopic Redshift For The Cl 0024+16 Multiple Arc System: Implications For The Central Mass Distribution, Tom Broadhurst, Xiaosheng Huang, Brenda Frye, Richard Ellis
Physics and Astronomy
We present a spectroscopic redshift of z = 1.675 for the well-known multiply lensed system of arcs seen in the z = 0.39 cluster Cl 0024+16. In contrast to earlier work, we find that the lensed images are accurately reproduced by a projected mass distribution which traces the locations of the brightest cluster elliptical galaxies, suggesting that the most significant minima of the cluster potential are not dynamically erased. The averaged mass profile is shallow and consistent with predictions of recent numerical simulations. The source redshift enables us to determine an enclosed cluster mass of M(<100 kpc h-1) = …
Implications Of Gamma-Ray Transparency Constraints In Blazars: Minimum Distances And Gamma-Ray Collimation, P. A. Becker, Menas Kafatos
Implications Of Gamma-Ray Transparency Constraints In Blazars: Minimum Distances And Gamma-Ray Collimation, P. A. Becker, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
We develop a general expression for the γ-γ absorption coefficient, αγγ, for γ-rays propagating in an arbitrary direction at an arbitrary point in space above an X-ray-emitting accretion disk. The X-ray intensity is assumed to vary as a power law in energy and radius between the outer disk radius, R0 , and the inner radius, Rm., which is the radius of marginal stability for a Schwarzschild black hole. We use our result for αγγ to calculate the γ-γ optical depth, Tγγ, for γ-rays created at height z and propagating at angle Φ relative to the disk axis, and we show …
Relativistic Particle Transport In Hot Accretion Disks, P. A. Becker, Menas Kafatos, M. Maisack
Relativistic Particle Transport In Hot Accretion Disks, P. A. Becker, Menas Kafatos, M. Maisack
Mathematics, Physics, and Computer Science Faculty Articles and Research
Accretion disks around rapidly rotating black holes provide one of the few plausible models for the production of intense radiation in AGNs above energies of several hundred MeV. The rapid rotation of the hole increases the binding energy per nucleon in the last stable orbit relative to the Schwarzschild case, and naturally leads to ion temperatures in the range 10^12-10^13 K for sub-Eddington accretion rates. The protons in the hot inner region of a steady, two-temperature disk form a reservoir of energy that is sufficient to power the observed EGRET outbursts if the black hole mass is 10^10 M0 • …