Distribution of the magnetic field relative to the plane of the Galaxy in the region of the Sagittarius spiral arm

Abstract

Faraday rotation data for 492 pulsars and more than 2,700 extragalactic radio sources were used to study the magnetic field, in detail, in the direction of Galactic longitude $33^o$ <l< $63^o$, which partially covers the Sagittarius spiral arm region. It was proposed that the Sagittarius spiral arm lies north of the h=-300 pc plane, where h is the distance from the Galactic plane. The (-) sign indicates that this plane is located in the southern hemisphere of the Galaxy. The magnetic field of the Sagittarius spiral arm is directed toward the Sun. This direction is close to the direction of the magnetic field of the northern hemisphere halo. The small absolute value of the rotation measures in the region south of the h=-300 pc plane is due solely to the contribution of the magnetic field of the southern hemisphere halo, which is directed opposite to the field of the northern hemisphere halo and the direction of the field in the Sagittarius arm. In the interarm region between the local Orion arm and the Sagittarius arm, the halo magnetic field extends to the Galactic plane, where a reversal of the magnetic fields of the halos of the northern and southern hemispheres occurs.