A5049389591- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Cosmology and Gravitation Theories
- Astronomy and Astrophysical Research
- Astrophysics and Cosmic Phenomena
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Solar and Space Plasma Dynamics
- Stellar, planetary, and galactic studies
- Scientific Research and Discoveries
- Photocathodes and Microchannel Plates
- Geophysics and Gravity Measurements
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Relativity and Gravitational Theory
- Atomic and Molecular Physics
- Particle Accelerators and Free-Electron Lasers
- Pulsars and Gravitational Waves Research
- Calibration and Measurement Techniques
- Adaptive optics and wavefront sensing
- Astronomical Observations and Instrumentation
- High-pressure geophysics and materials
- Advanced X-ray Imaging Techniques
- Magnetic confinement fusion research
- Quantum Mechanics and Applications
University of Alabama in Huntsville
2011-2024
SRON Netherlands Institute for Space Research
2007
Observatoire Midi-Pyrénées
2007
University of Alabama
2004
Council of Science Editors
2004
Universidad Alejandro de Humboldt
2001
University of California, Berkeley
1992-1997
University of California System
1996
The London College
1991
Imperial College London
1980-1989
The first all-sky survey for cosmic sources of extreme-ultraviolet radiation has been carried out with the UK Wide Field Camera on ROSAT. A reduction data yielded a catalogue 383 relatively bright EUV sources, forming WFC Bright Source Catalogue. This represents 30-fold increase in number astrophysical objects detected ~ 60–200 eV energy band and covers flux range, each two bands, more than 2000. search (typically 1-arcmin) error circles using variety catalogues SIMBAD base, identified...
The central region of the Coma cluster galaxies was observed in energy band from 0.065 to 0.245 kiloelectron volts by Deep Survey telescope aboard Extreme Ultraviolet Explorer. A diffuse emission halo angular diameter approximately 30 arc minutes detected. extreme-ultraviolet (EUV) level exceeds that expected x-ray temperature gas Coma. This suggests presence two more phases emitting gas, one at a 2 x 10(6) kelvin and other 8 10(5) kelvin. latter phase cools rapidly and, steady state, would...
An observation of M87, the central galaxy Virgo Cluster, was performed by deep survey telescope aboard Extreme-Ultraviolet Explorer, in 0.065-0.245 keV energy band. A point source and an extended emission halo radius ~20' are clearly visible data, represent first detection cluster gas EUV. The cannot be explained well-known at X-ray temperatures. Instead, it is necessary to introduce a second component, with temperature between 5 × 105 106 K. rapid cooling plasmas such temperatures implies...
We suggest that the luminous extreme-ultraviolet (EUV) emission has been detected recently from clusters of galaxies is inverse Compton scattering cosmic microwave background radiation by low-energy cosmic-ray electrons in intracluster medium. The would have Lorentz factors γ~300 and lose energy primarily emitting EUV radiation. These particles lifetimes comparable to Hubble time; thus, might represent a relic population rays produced nonthermal activity over history cluster. model naturally...
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or Einstein field equations sourced by a topological defect, \ie~a singularity of very specific form, result localised gravitational capable driving flat rotation (\ie~Keplerian circular orbits at constant speed for all radii) test masses on thin shell without any underlying mass. Moreover, large-scale structure which exploits this solution assembling concentrically number such defects can...
Abstract A set of temporal singularities (transients) in the mass-energy
density and pressure, bearing a specific mathematical structure which represents new solution to continuity equation
(\ie~conservation mass-energy) satisfying strong energy condition, is proposed account for expansion history homogeneous Universe, and
the formation binding large scale structures as continuum approximation their cumulative
effects. These are unobservable because they occur...
We report the detection of both soft and hard excess X-ray emission in cluster galaxies A2199, based upon spatially resolved spectroscopy with data from BeppoSAX, Extreme Ultraviolet Explorer, ROSAT missions. The is visible at radii larger than 300 kpc increases strength relative to isothermal component. total 0.1-100 keV luminosity this component 15% luminosity, but it dominates high low energies. argue that most plausible interpretation an inverse Compton interaction between cosmic...
view Abstract Citations (138) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The First Extreme Ultraviolet Explorer Source Catalog Bowyer, S. ; Lieu, R. Lampton, M. Lewis, J. Wu, X. Drake, Malina, F. (EUVE) has conducted an all-sky survey to locate and identify point sources of emission in four extreme ultraviolet wavelength bands centered at ~100, 200, 400, 600A. A companion deep a strip along half the ecliptic plane was simultaneously...
We have observed the rich cluster Abell 1795 for 90,000 s, using deep survey telescope aboard Extreme-Ultraviolet Explorer, with Lex/B (69-190 eV) passband filter. Very luminous emission was detected, a marked softening of spectrum toward limiting sensitivity radius 10' (~0.67 Mpc, assuming here and thereafter Hubble constant 75 km s−1 Mpc−1), where EUV intensity is 6 times higher than that expected from low-energy tail thermal X-ray emission, resulting luminosity (a model-independent...
We investigate a sample of 14 clusters galaxies observed with XMM-Newton in search for soft X-ray excess emission. In five these significant is evident. This compared the thermal emission from both hot intracluster gas and any cooling (flow) that may be present. A warm (kT=0.2 keV), extended (several Mpc), plasma component particularly clear outer parts cluster, where normal cluster weak. causes at low energies (below 0.4-0.5 as well O VII line redshift consistent origin, not easily...
The role of cosmic rays (CR) in the formation and evolution clusters galaxies has been much debated. It may well be related to other fundamental questions, such as mechanism which heats virializes intracluster medium (ICM), frequency at ICM is shocked. There now compelling evidence both from cluster soft excess (CSE) `hard-tail' emissions energies above 10 keV, that many are luminous sources inverse-Compton (IC) emission. This first direct measurement CR: technique free our uncertainties...
We present a method of directly testing whether time continues to have its usual meaning on scales ≤tP = (ℏG/c5)1/2 ≈ 5.4 × 10-44 s, the Planck time. According quantum gravity, t an event cannot be determined more accurately than standard deviation form σt/t a0(tP/t)α, where a0 and α are positive constants ~1; likewise, distances subject ultimate uncertainty cσt, c is speed light. As consequence, period wavelength light specified precisely; rather, they independently same intrinsic...
The WMAP Q, V, and W band radial profiles of temperature deviation the cosmic microwave background (CMB) were constructed for a sample 31 randomly selected nearby clusters galaxies in directions Galactic latitude $|b| >$ 30$^o$. compared detail with expected CMB Sunyaev-Zel'dovich effect (SZE) caused by these clusters, hot gas properties each cluster inferred observationally applying temperatures as measured ASCA to isothermal $β$ models ROSAT X-ray surface brightness profiles, point...
The study of soft X-ray emission 38 selected galaxy clusters observed by ROSAT PSPC indicates that the excess phenomenon may be a common occurrence in clusters. Excess radiation, above contribution from hot intra-cluster medium, is evident large fraction sources, and clearly detected with statistical significance deepest observations. investigation relies on new, high resolution 21 cm HI sample selection also features analysis infra-red images, to further ensure reliability results respect...
The aim of this paper is to re-examine the question average magnification in a universe with some inhomogeneously distributed matter. We present an analytic proof, valid under rather general conditions, including clumps any shape and size, strong lensing, that so long as are uncorrelated \emph{reciprocal} (in one several possible senses) precisely same homogeneous equal mean density. From result, we also show similar statement can be made about definition \emph{direct} magnification....
We present a list of 534 objects detected jointly in the Extreme Ultraviolet Explorer (EUVE) 100 Å all-sky survey and ROSAT X-Ray Telescope 0.25 keV band. The joint selection criterion permits use low count rate threshold each survey. This is roughly 60% used previous EUVE surveys, 166 listed here are new EUV sources, appearing neither Second Source Catalog nor Wide Field Camera Catalog. spatial distribution this catalog shows three features: an enhanced concentration Ursa Major, where...
We present results on the spectroscopic analysis of XMM-Newton EPIC data central 0.5 h Mpc regions clusters galaxies Coma, A1795, and A3112. The temperature hot intracluster gas as determined by modeling 2-7 keV PN MOS is consistent with that inferred from Fe XXV/Fe XXVI line ratio. A significant warm emission component at a level above systematic uncertainties evident in confirmed ROSAT PSPC for Coma A1795. nonthermal origin phenomenon cannot be ruled out current calibration accuracy, but...
The Virgo and A1795 clusters of galaxies were reobserved by the Extreme Ultraviolet Explorer with in situ background measurements pointing at small offsets. Earlier, a similar reobservational strategy applied to cluster A2199 revealed that radial profile was consistent flat distribution, therefore original method extracting EUV signals subtraction an asymptotically determined valid. It is shown here same conclusions hold for current sample. A model obtained from its known properties...
Several deep PSPC observations of the Coma Cluster reveal a very large scale halo soft X-ray emission, substantially in excess well-known radiation from hot intracluster medium. The previously reported central region cluster using lower sensitivity Extreme Ultraviolet Explorer (EUVE) and ROSAT data, is now evident out to radius 2.6 Mpc, demonstrating that clusters phenomenon cosmological significance. spectrum at these radii cannot be modeled nonthermally but consistent with original...
Since all of the five clusters galaxies observed by Extreme-Ultraviolet Explorer deep survey telescope are found to possess a diffuse EUV-emitting component that is unrelated hot intracluster medium (ICM) at X-ray temperatures, question concerning nature this new has been subject controversy. Here we present results an EUV and soft spatial analysis rich Abell 2199 1795. The emission does not resemble morphology clusters: cluster core, contours organized; larger radii, they anisotropic...
We report the detection of diffuse O VI λλ1032, 1038 emission in a 29 ks observation centered on Coma Cluster (l = 57.6, b +88.0) and an 11 toward Virgo 284.2, +74.5) through 30'' × aperture Far-Ultraviolet Spectroscopic Explorer (FUSE). The lines have redshift near zero are thus produced by gas our own Galaxy. Observed surface brightnesses 2000 ± 600 photons cm-2 s-1 sr-1 for each components spectrum 2900 700 1700 1032 Å lines, respectively, Virgo. These features similar strength to those...