Formation of large-scale magnetic structures associated with the Fermi bubbles

The Fermi bubbles are part of a complex region of the Milky Way. This region presents broadband extended non-thermal radiation, apparently coming from a physical structure rooted in the Galactic Centre and with a partly-ordered magnetic field threading it. We explore the possibility of an explosive origin for the Fermi bubble region to explain its morphology, in particular that of the large-scale magnetic fields, and provide context for the broadband non-thermal radiation. We perform 3D magnetohydrodynamical simulations of an explosion from a few million years ago that pushed and sheared a surrounding magnetic loop, anchored in the molecular torus around the Galactic Centre. Our results can explain the formation of the large-scale magnetic structure in the Fermi bubble region. Consecutive explosive events may match better the morphology of the region. Faster velocities at the top of the shocks than at their sides may explain the hardening with distance from the Galactic Plane found in the GeV emission. In the framework of our scenario, we estimate the lifetime of the Fermi bubbles as $2\times10^6$ yr, with a total energy injected in the explosion(s) $> 10^{55}$ ergs. The broadband non-thermal radiation from the region may be explained by leptonic emission, more extended in radio and X-rays, and confined to the Fermi bubbles in gamma rays.Comment: 5 pages, 4 figures, accepted for A&

New insights from recently migrated CROP multichannel seismic data at the outermost Calabrian arc accretionary wedge (Ionian sea)

This study addresses selected aspects of the stratigraphic-structural setting of the outermost Calabrian Arc accretionary wedge and underlines relationships between structural development and Messinian evaporite stratigraphy through the analysis of re-processed CROP multichannel seismic reflection profiles. A detailed seismostratigraphic analysis, calibrated with P-velocities compiled by previous works, images a general bipartition of the Messinian evaporite deposits: the transparent \uablower subunit\ubb appears to have undergone ductile-flow deformation\ubb, with the development of salt-cored thrusting structures, and the layered \uabupper subunit\ubb appears to be characterized by brittle deformation. The difference in both the seismic facies and the deformational style imaged for the Messinian evaporite unit allows a better defined unit stratigraphy that consists of a salt layer below and a gypsum and marl layer above. Lateral variations in composition and/or thickness of the Messinian evaporites are the local cause of the replacement of the transparent and layered subunits with a more chaotic facies as well as a change in the deformation style, with the development of double verging imbricated thrust sheets of the whole Messinian sequence. Most of the accreted outermost accretionary wedge is imaged to have resulted from the progressive piling up and associated thrusting of the Messinian evaporites and overlying Plio-Quaternary sediments; the gently dipping-reflector located at the base of the Messinian evaporites shows negative polarity at some places, suggesting that it acts as the d\ue9collement level. Active deformation occurs on the outermost accretionary wedge as related to subduction-driven shortening; further on, near-surface gravitational slide tectonics is imaged as related to a growing outermost wedge and favoured by the salt tectonics and/or to fluid overpressuring on the d\ue9collement level

Gamma-ray flares from red giant/jet interactions in AGN

Non-blazar AGN have been recently established as a class of gamma-ray sources. M87, a nearby representative of this class, show fast TeV variability on timescales of a few days. We suggest a scenario of flare gamma-ray emission in non-blazar AGN based on a red giant interacting with the jet at the base. We solve the hydrodynamical equations that describe the evolution of the envelope of a red giant blown by the impact of the jet. If the red giant is at least slightly tidally disrupted by the supermassive black hole, enough stellar material will be blown by the jet, expanding quickly until a significant part of the jet is shocked. This process can render suitable conditions for energy dissipation and proton acceleration, which could explain the detected day-scale TeV flares from M87 via proton-proton collisions. Since the produced radiation would be unbeamed, such an events should be mostly detected from non-blazar AGN. They may be frequent phenomena, detectable in the GeV-TeV range even up to distances of $\sim 1$ Gpc for the most powerful jets. The counterparts at lower energies are expected to be not too bright.} {M87, and nearby non-blazar AGN in general, can be fast variable sources of gamma-rays through red giant/jet interactions.Comment: 8 pages, 4 figure

Long-term Labor Force Exit and Economic Well-being: A Cross-National Comparison of Public and Private Income Support

N/A

Combined frequency-amplitude nonlinear modulation: theory and applications

In this work we formulate a generalized theoretical model to describe the nonlinear dynamics observed in combined frequency-amplitude modulators whose characteristic parameters exhibit a nonlinear dependence on the input modulating signal. The derived analytical solution may give a satisfactory explanation of recent laboratory observations on magnetic spin-transfer oscillators and fully agrees with results of micromagnetic calculations. Since the theory has been developed independently of the mechanism causing the nonlinearities, it may encompass the description of modulation processes of any physical nature, a promising feature for potential applications in the field of communication systems.Comment: 8 pages, 4 figures, to be published on IEEE Transactions on Magnetic

The J_1-J_2 model revisited : Phenomenology of CuGeO_3

We present a mean field solution of the antiferromagnetic Heisenberg chain with nearest (J_1) and next to nearest neighbor (J_2) interactions. This solution provides a way to estimate the effects of frustration. We calculate the temperature-dependent spin-wave velocity, v_s(T) and discuss the possibility to determine the magnitude of frustration J_2/J_1 present in quasi 1D compounds from measurements of v_s(T). We compute the thermodynamic susceptibility at finite temperatures and compare it with the observed susceptibility of the spin-Peierls compound CuGeO_3. We also use the method to study the two-magnon Raman continuum observed in CuGeO_3 above the spin-Peierls transition.Comment: Phys. Rev.

Multidisciplinary approach for outcropping and subsurface Permian-Cenozoic deepwater carbonates (Central Sicily): outcome for paleogeography of the Southern Tethyan continental margin

An integrated stratigraphic study of the outcropping and buried Permian-Cenozoic deep-water carbonate successions have been performed. These successions form some of the tectonic units, mostly buried beneath the Late Neogene sedimentary cover, in the fold and thrust belt of Central Sicily. Three main successions, pertaining to the well known Lercara, Imerese and Sicanian domains, have been reconstructed on the basis of a detailed facies analysis, seismostratigraphic interpretation, biostratigraphy (mostly based on palynological data) and comparison between outcropping and subsurface deep-water sediments. The main results reveal a continuous sedimentation of the deep-water Southern Tethyan Sicilian succession since the Permian to Cenozoic. In detail: a) the Permian-Middle Triassic terrigenous and carbonate deep-water successions, outcropping or buried in the Cerda, Lercara-Roccapalumba and Sosio Valley regions, are well comparable to each other and represent the common substrate of the Mesozoic-Paleogene Imerese and Sicanian carbonate successions; b) the Mesozoic-Paleogene deep-water carbonates, when compared among them, reveal the occurrence of different sedimentary successions (Imerese and Sicanian); c) the Oligo-Miocene foreland basin terrigenous sediments (Numidian flysch) clearly differ from the coeval foreland hemipelagic to open-shelf carbonates. The paleogeographic reconstruction envisages: a) during the Permian-Triassic, a wide subsident continental rifting area, bordered by a shallow-water domain periodically supplying the basin with calciturbiditic to gravity flows sedimentation (rift stage of the Southern Tethyan margin); b) during the Jurassic-Paleogene, two different deep-water basins developed in a context of a post-rift stage. The different sedimentation reflects the location of the Imerese and Sicanian basins, respectively, along adjacent rimmed shelf and stepped carbonate platform margins; c) the Oligo-Miocene sedimentation reflects the afore-mentioned different location of the two deep-water domains. Flysch deposits suggest that the Imerese was located near an accretionary prism, differently the Sicanian open-shelf carbonates and marls developed on a still undeformed foreland

Clouds and red giants interacting with the base of AGN jets

Extragalactic jets are formed close to supermassive black-holes in the center of galaxies. Large amounts of gas, dust, and stars cluster in the galaxy nucleus, and interactions between this ambient material and the jet base should be frequent, having dynamical as well as radiative consequences. This work studies the dynamical interaction of an obstacle, a clump of matter or the atmosphere of an evolved star, with the innermost region of an extragalactic jet. Jet mass-loading and the high-energy outcome of this interaction are briefly discussed. Relativistic hydrodynamical simulations with axial symmetry have been carried out for homogeneous and inhomogeneous obstacles inside a relativistic jet. These obstacles may represent a medium inhomogeneity or the disrupted atmosphere of a red giant star. Once inside the jet, an homogeneous obstacle expands and gets disrupted after few dynamical timescales, whereas in the inhomogeneous case, a solid core can smoothen the process, with the obstacle mass-loss dominated by a dense and narrow tail pointing in the direction of the jet. In either case, matter is expected to accelerate and eventually get incorporated to the jet. Particles can be accelerated in the interaction region, and produce variable gamma-rays in the ambient matter, magnetic and photon fields. The presence of matter clumps or red giants into the base of an extragalactic jet likely implies significant jet mass-loading and slowing down. Fast flare-like gamma-ray events, and some level of persistent emission, are expected due to these interactions.Comment: 13 pages, 15 Figures, accepted for publication in Astronomy and Astrophysic