Letter to the Editor

LABOCA and MAMBO-2 imaging of the dust ring of the Sombrero galaxy (NGC 4594)^*

¹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands e-mail: vlahakis@strw.leidenuniv.nl
² Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, Belgium
³ Astrophysics Group, Imperial College, Blackett Laboratory, Prince Consort Road, London SW7 2AZ, UK
⁴ ESO, Casilla 19001, Santiago 19, Chile

Received: 24 April 2008
Accepted: 16 May 2008

Abstract

The Sombrero galaxy (NGC 4594) is an Sa galaxy with a symmetric dust ring. We have used the Large APEX BOlometer CAmera (LABOCA) at 870 μm and the MAx-Planck Millimeter BOlometer (MAMBO-2) at 1.2 mm to detect the dust ring for the first time at submillimetre and millimetre wavelengths. We have constructed a model of the galaxy to separate the active galactic nucleus (AGN) and dust ring components. The ring radius at both 870 μm and 1.2 mm agrees well with the radius determined from optical absorption and atomic gas studies. The spectral energy distribution of the ring is well fitted by a single grey-body with dust emissivity index and a dust temperature  K. The dust mass of the ring is found to be   which, for a Galactic gas-to-dust ratio, implies a gas mass that is consistent with measurements from the literature.