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An asymmetric distribution of positrons in the Galactic disk revealed by γ-rays
Knödlseder, Jürgen; Winkler, Christoph; Diehl, Roland +8 more
Gamma-ray line radiation at 511keV is the signature of electron-positron annihilation. Such radiation has been known for 30years to come from the general direction of the Galactic Centre, but the origin of the positrons has remained a mystery. Stellar nucleosynthesis, accreting compact objects, and even the annihilation of exotic dark-matter parti…
Radial temperature profiles for a large sample of galaxy clusters observed with XMM-Newton
Molendi, S.; Leccardi, A.
Aims: We measure radial temperature profiles as far out as possible for a sample of ≈50 hot, intermediate redshift galaxy clusters, selected from the XMM-Newton archive, keeping systematic errors under control.
Methods: Our work is characterized by two major improvements. First, we used background modeling, rather than background subtraction, …
Turbulence transport throughout the heliosphere
Matthaeus, W. H.; Bieber, J. W.; Smith, C. W. +4 more
We employ a turbulence transport model to compute distributions of turbulence throughout the heliosphere. The model determines the radial dependence of three (coupled) quantities that characterize interplanetary turbulence, the energy per unit mass, the cross helicity or Alfvénicity, and a similarity length scale. A fourth integrated quantity, the…
Galaxy-cluster gas-density distributions of the representative XMM-Newton cluster structure survey (REXCESS)
Böhringer, H.; Arnaud, M.; Pointecouteau, E. +7 more
We present a study of the structural and scaling properties of the gas distributions in the intracluster medium (ICM) of 31 nearby (z < 0.2) clusters observed with XMM-Newton, which together comprise the Representative XMM-Newton Cluster Structure Survey (REXCESS). In contrast to previous studies, this sample is unbiased with respect to X-ray s…
Tidal heating and the long-term stability of a subsurface ocean on Enceladus
Nimmo, Francis; Roberts, James H.
Tidal dissipation has been suggested as the heat source for the south polar thermal anomaly on Enceladus. We find that under present-day conditions and assuming Maxwellian behavior, tidal dissipation is negligible in the silicate core. Dissipation may be significant in the ice shell if the shell is decoupled from the silicate core by a subsurface …
Dunes on Titan observed by Cassini Radar
Lorenz, R. D.; Callahan, P.; Lunine, J. I. +13 more
Thousands of longitudinal dunes have recently been discovered by the Titan Radar Mapper on the surface of Titan. These are found mainly within ±30° of the equator in optically-, near-infrared-, and radar-dark regions, indicating a strong proportion of organics, and cover well over 5% of Titan's surface. Their longitudinal duneform, interactions wi…
The Magnetic Landscape of the Sun's Polar Region
Lites, B. W.; Ichimoto, K.; Tsuneta, S. +11 more
We present observations of the magnetic landscape of the polar region of the Sun that are unprecedented in terms of spatial resolution, field of view, and polarimetric precision. They were carried out with the Solar Optical Telescope aboard Hinode. Using a Milne-Eddington inversion, we find many vertically oriented magnetic flux tubes with field s…
Black holes and core expansion in massive star clusters
Davies, M. B.; Mackey, A. D.; Wilkinson, M. I. +1 more
In this study we present the results from realistic N-body modelling of massive star clusters in the Magellanic Clouds. We have computed eight simulations with N ~ 105 particles; six of these were evolved for at least a Hubble time. The aim of this modelling is to examine in detail the possibility of large-scale core expansion in massiv…
Slow dust in Enceladus' plume from condensation and wall collisions in tiger stripe fractures
Schmidt, Jürgen; Spahn, Frank; Kempf, Sascha +1 more
One of the spectacular discoveries of the Cassini spacecraft was the plume of water vapour and icy particles (dust) originating near the south pole of Saturn's moon Enceladus. The data imply considerably smaller velocities for the grains than for the vapour, which has been difficult to understand. The gas and dust are too dilute in the plume to in…
An absorption origin for the X-ray spectral variability of MCG-6-30-15
Turner, T. J.; Reeves, J. N.; Miller, L.
Context: The Seyfert I galaxy MCG-6-30-15 shows one of the best examples of a broad “red wing” of emission in its X-ray spectrum at energies 2 < E < 6.4 keV, commonly interpreted as being caused by relativistically-blurred reflection close to the event horizon of the black hole.
Aims: We aim to test an alternative model in which absorpti…