Resolving the nuclear dust distribution of the Seyfert 2 galaxy NGC 3081

TL;DR

This study uses high-resolution far-infrared imaging from Herschel to analyze the dust distribution in the Seyfert 2 galaxy NGC 3081, revealing a compact torus and contributions from star-forming regions.

Contribution

First to combine Herschel FIR data with infrared SED modeling to constrain the size and structure of the nuclear dust torus in NGC 3081.

Findings

Nuclear torus size estimated at approximately 4 parsecs.

FIR data constrains the torus radial extent and cloud distribution.

Cold dust emission from circumnuclear star-forming ring detected beyond 200 microns.

Abstract

We report far-infrared (FIR) imaging of the Seyfert 2 galaxy NGC 3081 in the range 70-500 micron, obtained with an unprecedented angular resolution, using the Herschel Space Observatory instruments PACS and SPIRE. The 11 kpc (~70 arcsec) diameter star-forming ring of the galaxy appears resolved up to 250 micron. We extracted infrared (1.6-500 micron) nuclear fluxes, that is active nucleus-dominated fluxes, and fitted them with clumpy torus models, which successfully reproduce the FIR emission with small torus sizes. Adding the FIR data to the near- and mid-infrared spectral energy distribution (SED) results in a torus radial extent of Ro=4(+2/-1) pc, as well as in a flat radial distribution of the clouds (i.e. the q parameter). At wavelengths beyond 200 micron, cold dust emission at T=28+/-1 K from the circumnuclear star-forming ring of 2.3 kpc (~15 arcsec) in diameter starts making a contribution to the nuclear emission. The dust in the outer parts of the galaxy is heated by the interstellar radiation field (19+/-3 K).