Search results for "Jet"
showing 10 items of 4711 documents
Simulations of Precessing Jets
2003
We report on the results of a three-dimensional, relativistic, hydrodynamical simulation of a precessing jet through which a compact blob of matter is set to propagate. We conclude that the morphology of superluminal sources is the result of a complex combination of phase motions, viewing angle selection effects, and non-linear interactions between perturbations and the underlying jet and/or external medium.
Subparsec Polarimetric Radio Observations of 3C 120: A Close‐up Look at Superluminal Motion
1998
We present two-epoch polarimetric images of the radio galaxy 3C 120 obtained with the Very Long Baseline Array at 22 and 43 GHz. Because of the proximity of 3C 120 (z = 0.033), the 43 GHz observations allow us to observe superluminal motions with the highest resolution achieved to date, 0.07 h-1 pc. Up to ten different superluminal components, with velocities between 2.3 and 5.4 h-1c, can be observed in this active source, with approximately monthly ejections of new components. Polarization is observed in several components and at both frequencies, with peaks in the linearly polarized flux not always coincident with the peaks in total intensity. The orientation of the magnetic field is obse…
Afterglow model for the radio emission from the jetted tidal disruption candidate Swift J1644+57
2012
The recent transient event Swift J1644+57 has been interpreted as emission from a collimated relativistic jet, powered by the sudden onset of accretion onto a supermassive black hole following the tidal disruption of a star. Here we model the radio-microwave emission as synchrotron radiation produced by the shock interaction between the jet and the gaseous circumnuclear medium (CNM). At early times after the onset of the jet (t < 5-10 days) a reverse shock propagates through and decelerates the ejecta, while at later times the outflow approaches the Blandford-McKee self-similar evolution (possibly modified by additional late energy injection). The achromatic break in the radio light curve o…
Radio afterglow of the jetted tidal disruption event Swift J1644+57
2012
The recent transient event Swift J1644+57 has been interpreted as resulting from a relativistic outflow, powered by the accretion of a tidally disrupted star onto a supermassive black hole. This discovery of a new class of relativistic transients opens new windows into the study of tidal disruption events (TDEs) and offers a unique probe of the physics of relativistic jet formation and the conditions in the centers of distant quiescent galaxies. Unlike the rapidly-varying γ/X-ray emission from Swift J1644+57, the radio emission varies more slowly and is well modeled as synchrotron radiation from the shock interaction between the jet and the gaseous circumnuclear medium (CNM). Early after th…
Numerical study of emission and dynamics from a TDE-powered jet
2012
A transient event Swift J1644+57 is thought to be caused by the emission from a collimated relativistic jet. The jet, powered by the sudden onset of accretion onto a supermassive black hole following the tidal disruption of a star, collides with the gaseous circumnuclear medium and produces forward and reverse shocks which emit synchrotron radiation. We perform 1D and 2D relativistic hydrodynamic simulations using the MRGENESIS code. The aim of the simulations is to study the dynamics of a jet thought to exist in transient events such as Swift J1644+57, as discussed in recent literature. We discuss 1D and 2D jet evolution, on-axis radio light curves and differences between 1D and 2D jet dyn…
Effective Field Theory for Jet Processes
2015
Processes involving narrow jets receive perturbative corrections enhanced by logarithms of the jet opening angle and the ratio of the energies inside and outside the jets. Analyzing cone-jet processes in effective field theory, we find that in addition to soft and collinear fields their description requires degrees of freedom which are simultaneously soft and collinear to the jets. These collinear-soft particles can resolve individual collinear partons, leading to a complicated multi-Wilson-line structure of the associated operators at higher orders. Our effective field theory provides, for the first time, a factorization formula for a cone-jet process, which fully separates the physics at …
Dense jet modelling applied to the design of dense effluent diffusers
2004
A model aimed at predicting the behavior of inclined dense jets in a stagnant environment was proposed. The model takes into account four jet parameters (flow rate, density, inclination and diameter) and results in a set of algebraic and ordinary differential equations, which are easily solved by simple (standard) numerical methods. Model results include information on the trajectory, spreading and dilution of the inclined dense jets. Model predictions were compared with experimental data obtained with different nozzle diameters, jet flow rates, jet densities and nozzle inclinations. Despite the wide range encompassed by the experimental data analyzed, model predictions were always found to…
All Master Integrals for Three-Jet Production at Next-to-Next-to-Leading Order
2019
We evaluate analytically all previously unknown nonplanar master integrals for massless five-particle scattering at two loops, using the differential equations method. A canonical form of the differential equations is obtained by identifying integrals with constant leading singularities, in D space-time dimensions. These integrals evaluate to Q-linear combinations of multiple polylogarithms of uniform weight at each order in the expansion in the dimensional regularization parameter and are in agreement with previous conjectures for nonplanar pentagon functions. Our results provide the complete set of two-loop Feynman integrals for any massless 2→3 scattering process, thereby opening up a ne…
Jet-hadron correlations measured relative to the second order event plane in Pb-Pb collisions at sNN=2.76TeV
2020
The quark gluon plasma produced in ultrarelativistic heavy-ion collisions at the Large Hadron Collider (LHC) can be studied by measuring the modifications of jets formed by hard scattered partons which interact with the medium. We studied these modifications via angular correlations of jets with charged hadrons for jets with momenta 20
Comparison of Fragmentation Functions for Jets Dominated by Light Quarks and Gluons from pp and Pb+Pb Collisions in ATLAS
2019
Charged-particle fragmentation functions for jets azimuthally balanced by a high-transverse-momentum, prompt, isolated photon are measured in 25 pb^{-1} of pp and 0.49 nb^{-1} of Pb+Pb collision data at 5.02 TeV per nucleon pair recorded with the ATLAS detector at the Large Hadron Collider. The measurements are compared to predictions of Monte Carlo generators and to measurements of inclusively selected jets. In pp collisions, a different jet fragmentation function in photon-tagged events from that in inclusive jet events arises from the difference in fragmentation between light quarks and gluons. The ratios of the fragmentation functions in Pb+Pb events to that in pp events are used to e…