Radio polarization and sub-millimeter observations of the Sombrero galaxy (NGC 4594)

Large-scale magnetic field configuration and dust emission

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: mkrause@mpifr-bonn.mpg.de
² European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago 19, Chile

Received: 7 July 2005
Accepted: 14 October 2005

Abstract

We observed the nearby early-type spiral galaxy NGC 4594 (M 104, Sombrero galaxy) with the Very Large Array at 4.86 GHz, with the Effelsberg 100-m telescope at 8.35 GHz as well as with the Heinrich Hertz Telescope at 345 GHz in radio continuum. The 4.86 and 8.35 GHz data contain polarization information and hence information about the magnetic fields: we detected a large-scale magnetic field which is to our knowledge the first detection of a large-scale magnetic field in an Sa galaxy in the radio range. The magnetic field orientation in M 104 is predominantly parallel to the disk but has also vertical components at larger z-distances from the disk. This field configuration is typical for normal edge-on spiral galaxies. The 345 GHz data pertain to the cold dust content of the galaxy. Despite the optical appearance of the object with the huge dust lane, its dust content is smaller than that of more late-type spirals.