To understand how massive galaxies at high-$z$ co-evolve with enormous
reservoirs of halo gas, it is essential to study the coldest phase of the
circum-galactic medium (CGM), which directly relates ...to stellar growth. The
SUPERCOLD-CGM survey is the first statistical survey of cold molecular gas on
CGM scales. We present ALMA+ACA observations of CO(4-3) and continuum emission
from 10 Enormous Ly$\alpha$ Nebula (ELANe) around ultraluminous type-I QSOs at
$z\sim2$. We detect CO(4-3) in 100$\%$ of our targets, with 60$\%$ showing
extended CO on scales of 15$-$100 kpc. Q1228+3128 reveals the most extended
CO(4-3) reservoir of $\sim$100 kpc and is the only radio-loud target in our
sample. The CO reservoir is located along the radio axis, which could indicate
a link between the inner radio-jet and cold halo gas. For the other five
radio-quiet ELANe, four of them show extended CO(4-3) predominantly in the
direction of their companions. These extended CO(4-3) reservoirs identify
enrichment of the CGM, and may potentially contribute to widespread star
formation. However, there is no evidence from CO(4-3) for diffuse molecular gas
spread across the full extent of the Ly$\alpha$ nebulae. One target in our
sample (Q0107) shows significant evidence for a massive CO disk associated with
the QSO. Moreover, 70$\%$ of our QSO fields contain at least one CO companion,
two of which reveal extended CO emission outside the ELANe. Our results provide
insight into roles of both the cold CGM and companions in driving the early
evolution of massive galaxies.
This invaluable book provides a unique opportunity to embrace the complex and fascinating theory of relaxation processes in magnetized plasmas, both in astrophysics and in controlled fusion plasmas. ...The subjects range from dynamo and reconnection processes in magneto-hydrodynamics and electromagnetic turbulence to fast transport events in self-organized turbulence. Such phenomena, recognized as key bolts in our present understanding, turn out to be extremely challenging for theoretical models. This book efficiently helps to bridge our understanding and description of such processes, analogously observed in laboratory and astrophysical plasmas.
The energy spectrum of cosmic rays above 2.5 x 10;{18} eV, derived from 20,000 events recorded at the Pierre Auger Observatory, is described. The spectral index gamma of the particle flux, J ...proportional, variantE;{-gamma}, at energies between 4 x 10;{18} eV and 4 x 10;{19} eV is 2.69+/-0.02(stat)+/-0.06(syst), steepening to 4.2+/-0.4(stat)+/-0.06(syst) at higher energies. The hypothesis of a single power law is rejected with a significance greater than 6 standard deviations. The data are consistent with the prediction by Greisen and by Zatsepin and Kuz'min.
Transport barriers at the plasma edge are key elements of high confinement regimes in fusion devices. In typical configurations, such barriers are not stable but exhibit quasi-periodic relaxation ...oscillations. In this work, one-dimensional and zero-dimensional models for such oscillations are presented that give insight into the underlying mechanisms which are found to be intrinsically nonlinear. The models are systematically derived from three-dimensional turbulence simulations based on a fluid description of the plasma. In these simulations, a transport barrier is generated by an imposed E × B shear flow. This barrier exhibits quasiperiodic relaxation oscillations even if the E × B shear flow is frozen. The models presented here are therefore different from those based on turbulent shear flow generation. They allow to isolate and illustrate a different mechanism for barrier oscillations. Furthermore, these models reproduce regimes characterized by a decrease of the oscillation frequency with the E × B flow shear.
A major goal in fusion research is understanding the anomalous thermal transport of energy and particles in a tokamak. In particular, a crucial issue is the origin of its empirical dependence on the ...various dimensionless parameters controlling the energy confinement. This paper addresses the impact of ion-ion collisions and of self-generated zonal flows (largescale E × B sheared poloidal flows) on turbulent ion thermal transport, in the core of a tokamak plasma. A three-dimensional fluid model is used, which describes flux-driven electrostatic plasma turbulence, generated by Ion Temperature Gradient (ITG) instabilities. The model includes curvature effects, parallel Landau damping and a collisional damping of the poloidal flows. Simulation results show a stabilization of the turbulence and a rise of the energy confinement time when the collisionality is lowered, that is when the zonal flows are weakly damped by ion-ion collisions. The mechanism responsible for the turbulence stabilization at low collisionality is identified as the non-linear upshift of the effective threshold for the ITG turbulence onset. This upshift is governed by an increase of the zonal flow shear.
The spontaneous pedestal formation above a power threshold at the edge of magnetically confined plasma is modelled for the first time in flux driven three-dimensional fluid simulations of ...electromagnetic turbulence with the code EMEDGE3D. The role of the collisional friction between trapped and passing particles is shown to be the key ingredient for shearing the radial electric field, hence stabilizing the turbulence, rather than the Maxwell and Reynolds stresses. The isotope effect, observed in many tokamaks worldwide, is recovered in EMEDGE3D simulations: the power threshold for pedestal formation is lower for Tritium than for Deuterium. The turbulence auto-correlation time is found to increase with the ion mass easing the radial electric shear stabilization, hence the pedestal formation.
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