Letter to the Editor

The extent of dust in NGC 891 from Herschel/SPIRE images^⋆

¹ INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Florence, Italy
e-mail: sbianchi@arcetri.astro.it
² Institute of Astronomy and Astrophysics, National Obs. of Athens, I. Metaxa and Vas. Pavlou, P. Penteli, 15236 Athens, Greece
e-mail: xilouris@astro.noa.gr

Received: 23 February 2011
Accepted: 8 June 2011

Abstract

We analyse Herschel/SPIRE images of the edge-on spiral galaxy NGC 891 at 250, 350, and 500 μm. Using a 3D radiative transfer model we confirm that the dust has radial fall-off similar to the stellar disk. The dust disk shows a break at about 12 kpc from the centre, where the profile becomes steeper. Beyond this break, emission can be traced up to 90% of the optical disk on the NE side. To the SW, we confirm dust emission associated with the extended, asymmetric HI disk, previously detected by the Infrared Space Observatory (ISO). This emission is marginally consistent with the large diffuse dust disk inferred from radiative transfer fits to optical images. No excess emission is found above the plane beyond that of the thin, unresolved, disk.