Revisiting Rotation Measures from the Canadian Galactic Plane Survey: the Magnetic Field in the Disk of the Outer Galaxy

Abstract

Faraday rotation provides a valuable tracer of magnetic fields in the interstellar medium; catalogs of Faraday rotation measures provide key observations for studies of the Galactic magnetic field. We present a new catalog of rotation measures derived from the Canadian Galactic Plane Survey, covering a large region of the Galactic plane spanning 52along with northern and southern latitude extensions around l ≈ 105 • . We have derived rotation measures for 2234 sources (4 of which are known pulsars), 75% of which have no previous measurements, over an area of approximately 1300 square degrees. These new rotation measures increase the measurement density for this region of the Galactic plane by a factor of two.1 Faraday-simple refers to a line of sight with a single dominant source of polarized emission, with all of that emission undergoing the same amount of Faraday rotation. Lines of sight with multiple polarized components with different Faraday rotation are called Faraday-complex.