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Astrophysics papers — page 11

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Ultimate synchrotron cutoff in gamma-ray spectra of blazars as a signature of the converter mechanism
There is a robust upper limit on the energy of synchrotron radiation in high-energy astrophysics: m e c2 /α, where α= 1/137 is the fine structure constant and the value refers to the…
Boris E. Stern, Yana Y. TikhomirovDec 17, 2008
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The Hard X-ray Spectral Evolution in XRBs, AGNs and ULXs
We explore the relationship between the hard X-ray photon index Γ and the Eddington ratio (ξ=LX(0.5-25 keV)/LEdd) in six XRBs. We find that different XRBs follow different anti-correlations…
Qingwen Wu, Minfeng GuDec 17, 2008
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Unveiling the dominant gas heating mechanism in local LIRGs and ULIRGs
We show preliminary results from a sample of Luminous and Ultra-Luminous Infrared Galaxies (LIRGs and ULIRGs, respectively) in the local universe, obtained from observations using the Very Large…
Miguel A. Perez-Torres, Antxon Alberdi, Cristina Romero-Canizales et al.Dec 17, 2008
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Evolution of dwarf early-type galaxies I. Spatially resolved stellar populations and internal kinematics of Virgo cluster dE/dS0 galaxies
Understanding the origin and evolution of dwarf early-type galaxies remains an important open issue in modern astrophysics. Internal kinematics of a galaxy contains signatures of violent phenomena…
Igor ChilingarianDec 17, 2008
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Photometric Studies of a WZ Sge-Type Dwarf Nova Candidate, ASAS160048-4846.2
We report on our time-resolved CCD photometry during the 2005 June superoutburst of a WZ Sge-type dwarf nova candidate, ASAS 160048-4846.2. The ordinary superhumps underwent a complex evolution…
Yuichi Soejima, Akira Imada, Daisaku Nogami et al.Dec 17, 2008
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A short answer to critics of our article "Eppur si espande" [arXiv:astro-ph/0612155]
Recently [arXiv:astro-ph/0612155] we presented a formal mathematical proof that, contrary to a widespread misconception, cosmological expansion cannot be understood as the motion of galaxies in…
Marek A. Abramowicz, Stanislaw Bajtlik, Jean-Pierre Lasota et al.Dec 17, 2008
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Persistent fluctuations in the distribution of galaxies from the Two degree Field Galaxy Redshift Survey
We apply the scale-length method to several three dimensional samples of the Two degree Field Galaxy Redshift Survey. This method allows us to map in a quantitative and powerful way large scale…
Francesco Sylos Labini, Nikolay L. Vasilyev, Yurij V. BaryshevDec 17, 2008
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The Structures of Distant Galaxies - III: The Merger History of over 20,000 Massive Galaxies at z < 1.2
Utilizing deep Hubble Space Telescope imaging from the two largest field galaxy surveys, the Extended Groth Strip (EGS) and the COSMOS survey, we examine the structural properties, and derive the…
Christopher J. Conselice, Cui Yang, Asa F. L. BluckDec 17, 2008
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Non thermal emission from microquasar/ISM interaction
The interaction of microquasar jets with their environment can produce non-thermal radiation as is the case for extragalactic outflows impacting on their surroundings. We have developed an analytical…
P. Bordas, V. Bosch-Ramon, J. M. Paredes et al.Dec 17, 2008
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Local effects in astrometric binary orbits: perspective transformation and light-travel time
In order to get astrometric parameters achieving the precision permitted by the the forthcoming generation of astrometri cmeasurements, it will be necessary to take into account effects that were…
J. -L. HalbwachsDec 17, 2008
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A pilot survey of stellar tidal streams in nearby spiral galaxies
Within the hierarchical framework for galaxy formation, merging and tidal interactions are expected to shape large galaxies to this day. While major mergers are quite rare at present, minor mergers…
David Martinez-Delgado, R. Jay Gabany, Jorge Penarrubia et al.Dec 17, 2008
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Constraints on accelerating universe using ESSENCE and Gold supernovae data combined with other cosmological probes
We use recently observed data: the 192 ESSENCE type Ia supernovae (SNe Ia), the 182 Gold SNe Ia, the 3-year WMAP, the SDSS baryon acoustic peak, the X-ray gas mass fraction in clusters and the…
Jianbo Lu, Lixin Xu, Molin Liu et al.Dec 17, 2008
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Reconnectionless CME eruption: putting the Aly-Sturrock conjecture to rest
We demonstrate that magnetic reconnection is not necessary to initiate fast CMEs. The Aly-Sturrock conjecture states that the magnetic energy of a given force free boundary field is maximized when…
L. A. Rachmeler, C. E. DeForest, C. C. KankelborgDec 17, 2008
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Eccentricity modulation of a close-in planet by a companion - application to GJ 436 system
GJ 436b is a Neptune-size planet with 23.2 Earth masses in an elliptical orbit of period 2.64 days and eccentricity 0.16. With a typical tidal dissipation factor (Q' ~ 106) as that of a giant…
Tong Xiao, Ji-Lin ZhouDec 17, 2008
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Light element abundances in carbon-enhanced metal-poor stars
We model the evolution of the abundances of light elements in carbon-enhanced metal-poor (CEMP) stars, under the assumption that such stars are formed by mass transfer in a binary system. We have…
Richard J. StancliffeDec 17, 2008
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Three-Dimensional Simulations of Dynamics of Accretion Flows Irradiated by a Quasar
We study the axisymmetric and non-axisymmetric, time-dependent hydrodynamics of gas that is under the influence of the gravity of a super massive black hole (SMBH) and the radiation force produced by…
Ryuichi Kurosawa, Daniel ProgaDec 17, 2008
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Grid Based Linear Neutrino Perturbations in Cosmological N-body Simulations
We present a novel, fast and precise method for including the effect of light neutrinos in cosmological N-body simulations. The effect of the neutrino component is included by using the linear theory…
Jacob Brandbyge, Steen HannestadDec 17, 2008
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The Diffuse Supernova Neutrino Background is detectable in Super-Kamiokande
The Diffuse Supernova Neutrino Background (DSNB) provides an immediate opportunity to study the emission of MeV thermal neutrinos from core-collapse supernovae. The DSNB is a powerful probe of…
Shunsaku Horiuchi, John F. Beacom, Eli DwekDec 16, 2008
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The halo merger rate in the Millennium Simulation and implications for observed galaxy merger fractions
We developed a new method to extract halo merger rates from the Millennium Simulation. First, by removing superfluous mergers that are artifacts of the FOF halo finder, we find a lower merger rate…
S. Genel, R. Genzel, N. Bouché et al.Dec 16, 2008
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Collapse Barriers and Halo Abundance: Testing the Excursion Set Ansatz
Our heuristic understanding of the abundance of dark matter halos centers around the concept of a density threshold, or "barrier", for gravitational collapse. If one adopts the ansatz that…
Brant Robertson, Andrey Kravtsov, Jeremy Tinker et al.Dec 16, 2008
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The UKIRT Wide Field Camera ZYJHK Photometric System: Calibration from 2MASS
In this paper we describe the photometric calibration of data taken with the near-infrared Wide Field Camera (WFCAM) on the United Kingdom Infrared Telescope (UKIRT). The broadband ZYJHK data are…
S. T. Hodgkin, M. J. Irwin, P. C. Hewett et al.Dec 16, 2008
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Turbulent dynamos in spherical shell segments of varying geometrical extent
We use three-dimensional direct numerical simulations of the helically forced magnetohydrodynamic equations in spherical shell segments in order to study the effects of changes in the geometrical…
Dhrubaditya Mitra, Reza Tavakol, Axel Brandenburg et al.Dec 16, 2008
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Mutual Orbits and Masses of Six Transneptunian Binaries
We present Hubble Space Telescope observations of six binary transneptunian systems: 2000 QL251, 2003 TJ58, 2001 XR254, 1999 OJ4, (134860) 2000 OJ67, and 2004 PB108. The mutual orbits of these…
W. M. Grundy, K. S. Noll, M. W. Buie et al.Dec 16, 2008
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Cross-Correlation between Damped Ly-alpha Systems and Ly-break Galaxies in Cosmological SPH Simulations
We calculate the cross-correlation function (CCF) between damped Ly-a systems (DLAs) and Lyman break galaxies (LBGs) using cosmological hydrodynamic simulations at z=3. We compute the CCF with two…
Tae Song Lee, Kentaro Nagamine, Lars Hernquist et al.Dec 16, 2008
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Reconstructing Baryon Oscillations: A Lagrangian Theory Perspective
Recently Eisenstein and collaborators introduced a method to `reconstruct' the linear power spectrum from a non-linearly evolved galaxy distribution in order to improve precision in measurements…
Nikhil Padmanabhan, Martin White, J. D. CohnDec 16, 2008
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