3D relativistic MHD numerical simulations of X-shaped radio sources

¹ INAF/Osservatorio Astrofisico di Torino, Strada Osservatorio 20, 10025 Pino Torinese, Italy
e-mail: rossi@oato.inaf.it
² Dipartimento di Fisica, Università degli Studi di Torino, via Pietro Giuria 1, 10125 Torino, Italy

Received: 10 February 2017
Accepted: 18 May 2017

Abstract

Context. A significant fraction of extended radio sources presents a peculiar X-shaped radio morphology: in addition to the classical double lobed structure, radio emission is also observed along a second axis of symmetry in the form of diffuse wings or tails. In a previous investigation we showed the existence of a connection between the radio morphology and the properties of the host galaxies. Motivated by this connection we performed two-dimensional numerical simulations showing that X-shaped radio sources may naturally form as a jet propagates along the major axis a highly elliptical density distribution, because of the fast expansion of the cocoon along the minor axis of the distribution.

Aims. We intend to extend our analysis by performing three-dimensional numerical simulations and investigating the role of different parameters in determining the formation of the X-shaped morphology.

Methods. The problem is addressed by numerical means, carrying out three-dimensional relativistic magnetohydrodynamic simulations of bidirectional jets propagating in a triaxial density distribution.

Results. We show that only jets with power ≲ 10⁴⁴ erg s^-1 can give origin to an X-shaped morphology and that a misalignment of 30° between the jet axis and the major axis of the density distribution is still favourable to the formation of this kind of morphology. In addition we compute synthetic radio emission maps and polarization maps.

Conclusions. In our scenario for the formation of X-shaped radio sources only low power FRII can give origin to such kind of morphology. Our synthetic emission maps show that the different observed morphologies of X-shaped sources can be the result of similar structures viewed under different perspectives.