Investigating the dusty torus of Seyfert galaxies using SOFIA/FORCAST photometry

TL;DR

This study uses SOFIA/FORCAST infrared imaging to analyze the dusty torus in Seyfert galaxies, revealing extended emission and refining models of the torus structure and size.

Contribution

First infrared detection of extended emission in Seyfert galaxies at 31.5 microns and improved modeling of the torus structure using new data.

Findings

Extended 31 micron emission tentatively detected in Seyfert galaxies.

Inclusion of 31.5 micron flux alters torus model parameters.

Torus outer radii range from less than 1 pc to 8.4 pc.

Abstract

We present 31.5 micron imaging photometry of 11 nearby Seyfert galaxies observed from the Stratospheric Observatory For Infrared Astronomy (SOFIA) using the Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST). We tentatively detect extended 31 micron emission for the first time in our sample. In combination with this new data set, subarcsecond resolution 1-18 micron imaging and 7.5-13 micron spectroscopic observations were used to compute the nuclear spectral energy distribution (SED) of each galaxy. We found that the turnover of the torus emission does not occur at wavelengths <31.5 micron, which we interpret as a lower-limit for the wavelength of peak emission. We used CLUMPY torus models to fit the nuclear infrared (IR) SED and infer trends in the physical parameters of the AGN torus for the galaxies in the sample. Including the 31.5 micron nuclear flux in the SED 1) reduces the number of clumpy torus models compatible with the data, and 2) modifies the model output for the outer radial extent of the torus for 10 of the 11 objects. Specifically, six (60%) objects show a decrease in radial extent while four (40%) show an increase. We find torus outer radii ranging from <1pc to 8.4 pc