Suchergebnisse

This is the second of a series of two papers that deepen our understanding of the transversal structure and the properties of recollimation shocks of axisymmetric, relativistic, superfast magnetosonic, overpressured jets. They extend previous work that characterized these properties in connection with the dominant type of energy (internal, kinetic, or magnetic) in the jet to models with helical magnetic fields with larger magnetic pitch angles and force-free magnetic fields. In the first paper of this series, the magnetohydrodynamical models were computed following an approach that allows studying the structure of steady, axisymmetric, relativistic (magnetized) flows using one-dimensional time-dependent simulations. In this paper, synthetic radio images of the magnetohydrodynamical models are produced based on two different models to connect the thermal particle population, modeled by the hydrodynamical code, and the nonthermal particle population (added in post-processing) that causes the synchrotron radiation. The role of the magnetic tension and the Lorentz force in modeling the observational appearance of jets, namely the cross-section emission asymmetries, spine brightening, relative intensity of the knots, and polarized emission is analyzed. A cross-section emission asymmetry caused by a differential change in the angle between the helical magnetic field and the line of sight across the jet width is observed in all models and for both synchrotron emission approximations, as expected from a purely geometrical origin, for viewing angles < 10°. Models with the highest magnetizations and/or magnetic pitch angles lead to an uneven distribution of the internal energy as a consequence of the larger relative magnetic tension and radial Lorentz force, which translates into a spine brightening in the total and linearly polarized intensity maps. Force-free models display a distinct spine brightening that originates in the radial gradient of the axial magnetic field. Highly magnetized jets with large toroidal fields tend to have weaker shocks and correspondingly weaker radio knots. Signatures of this toroidal field can be found in the linearly polarized synchrotron emission for jets with large enough magnetic pitch angles and large enough viewing angles. © ESO 2021. ; AF and JLG acknowledge financial support from the Spanish Ministerio de Economía y Competitividad (grants AYA2016-80889-P, PID2019-108995GB-C21), the Consejería de Economía, Conocimiento, Empresas y Universidad of the Junta de Andalucía (grant P18-FR-1769), the Consejo Superior de Investigaciones Científicas (grant 2019AEP112), and the State Agency for Research of the Spanish MCIU through the Center of Excellence Severo Ochoa award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). JMM and MP acknowledge financial support from the Spanish Ministerio de Economía y Competitividad (grant AYA2016-77237-C3-3-P), the Spanish Ministerio de Ciencia (PID2019-107427GB-C33), and from the local Autonomous Government (Generalitat Valenciana, grant PROME-TEO/2019/071). JMM acknowledges further financial support from the Spanish Ministerio de Economía y Competitividad (grant PGC2018-095984-B-I00). MP acknowledges further financial support from the Spanish Ministerio de Ciencia through grant PID2019-105510GB-C31. This research made use of Python (http://www.python.org), Numpy (van der Walt et al. 2011), Pandas (McKinney et al. 2010), and Matplotlib (Hunter 2007). We also made use of Astropy (http://www.astropy.org), a community-developed core Python package for Astronomy (Astropy Collaboration 2013, 2018). ; Peer reviewed

This is the first of a series of two papers that deepen our understanding of the transversal structure and the properties of recollimation shocks of axisymmetric, relativistic, superfast magnetosonic, overpressured jets. They extend previous work that characterized these properties in connection with the dominant type of energy (internal, kinetic, or magnetic) in the jet to models with helical magnetic fields with larger magnetic pitch angles and force-free magnetic fields. In this paper, the magnetohydrodynamical models were computed following an approach that allows studying the structure of steady, axisymmetric, relativistic (magnetized) flows using one-dimensional time-dependent simulations. In these approaches, the relevance of the magnetic tension and of the Lorentz force in shaping the internal structure of jets (transversal structure, radial oscillations, and internal shocks) is discussed. The radial Lorentz force controls the jet internal transversal equilibrium. Hence, highly magnetized non-force-free jets exhibit a thin spine of high internal energy around the axis. The properties of the recollimation shocks and sideways expansions and compressions of the jet result from the total pressure mismatch at the jet surface, which among other factors depends on the magnetic tension and the magnetosonic Mach number of the flow. Hot jets with low Mach number tend to have strong oblique shocks and wide radial oscillations. Highly magnetized jets with large toroidal fields tend to have weaker shocks and radial oscillations of smaller amplitude. In the second paper, we present synthetic synchrotron radio images of the magnetohydrodynamical models that are produced at a post-processing phase, focusing on the observational properties of the jets, namely the top-down emission asymmetries, spine brightening, the relative intensity of the knots, and polarized emission. © ESO 2021. ; JMM and MP acknowledge financial support from the Spanish Ministerio de Economia y Competitividad (grant AYA2016-77237-C33-P), the Spanish Ministerio de Ciencia (PID2019-107427GB-C33), and from the local Autonomous Government (Generalitat Valenciana, grant PROMETEO/2019/071). JMM acknowledges further financial support from the Spanish Ministerio de Economia y Competitividad (grant PGC2018-095984-B-I00). MP acknowledges further financial support from the Spanish Ministerio de Ciencia through grant PID2019-105510GB-C31. AF and JLG acknowledge financial support from the Spanish Ministerio de Economia y Competitividad (grants AYA2016-80889-P, PID2019-108995GB-C21), the Consejeria de Economia, Conocimiento, Empresas y Universidad of the Junta de Andalucia (grant P18-FR-1769), the Consejo Superior de Investigaciones Cientificas (grant 2019AEP112), and the State Agency for Research of the Spanish MCIU through the Center of Excellence Severo Ochoa award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709). This research made use of Python (http://www.python.org), Numpy (van der Walt et al. 2011), Pandas (McKinney 2010), and Matplotlib (Hunter 2007). We also made use of Astropy (http://www.astropy.org), a community-developed core Python package for Astronomy (Astropy Collaboration 2013, 2018). ; Peer reviewed