A Study of Radio Polarization in Protostellar Jets

CÉCERE, M.; VELÁZQUEZ, P; ARAUDO, A.; DE COLLE, F.; ESQUIVEL, A.; CARRASCO-GONZALEZ, C.; RODRÍGUEZ, L. F.

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 2016

0004-637X

Synchrotron radiation is commonly observed in connection with shocks ofdifferent velocities, ranging from relativistic shocks associated withactive galactic nuclei, gamma-ray bursts or microquasars to weakly- ornon-relativistic flows as those observed in supernovaremnants. Recent observations of synchrotron emission in protostellar jets areimportant not only because they extend the range over which theacceleration process works, but also because they allow to determinethe jet and/or interstellar magnetic field structure, thus givinginsights on the jet ejection and collimation mechanisms. In this paper, wecompute for the first time polarized (synchrotron) and non polarized(thermal X-ray) synthetic emission maps from axisymmetricalsimulations of magnetized protostellar jets.  We consider models withdifferent jet velocities and variability, as well as toroidal orhelical magnetic field.  Our simulations show that variable,low-density jets with velocities $sim$ 1000 km s$^{-1}$ and $sim$ 10times lighter than the environment can produce internal knots withsignificant synchrotron emission, and thermal X-rays in the shockedregion of the leading bow shock moving in a dense medium. While models with a purely toroidal magnetic field show a very  large degree of polarization, models with helical magnetic field  show lower values and a decrease of the degree of polarization, in  agreement with observations of protostellar jets.