# AGN torus detectability at sub-millimeter wavelengths: What to expect from ALMA continuum data

## TL;DR

This study assesses the potential for detecting AGN dusty tori at sub-millimeter wavelengths using ALMA, combining theoretical models and observational data to identify promising targets and optimal observing strategies.

## Contribution

It integrates theoretical modeling with observational analysis to evaluate AGN torus detectability at sub-mm wavelengths, providing practical guidelines for future ALMA observations.

## Key findings

- Detection likelihood increases at higher ALMA frequencies (666 GHz).
- Bright AGN with ~1 mJy flux at 12 microns are detectable with reasonable ALMA observing times.
- Highly accreting sources like IZw1 are promising candidates for torus detection.

## Abstract

We study the detectability of the emission associated with the AGN dusty structure at sub-mm wavelengths using ALMA, in a theoretical and observational way. Theoretically, we use the Clumpy models from Nenkova et al. together with the mid-infrared to X-ray and the radio fundamental plane scaling relations. We find that it is more likely to detect bigger and denser dusty tori at the highest ALMA frequency (666 GHz/450 micron). We also find that with 1h at 353 GHz/850 micron and 10h at 666 GHz/450 micron we can detect, with a high detection limit, a 1 mJy torus (characteristic of bright AGN). This means, an object for which the unresolved SED at 12 micron has a flux ~1mJy. Observationally, we use four prototypical AGN: NGC\,1052 (low-luminosity AGN), NGC\,1068 (Type-2), NGC\,3516 (Type 1.5), and IZw1 (QSO), with radio, sub-millimeter, and mid-IR data available. All the mid-infrared spectra are best fit with the smooth model reported by Fritz et al. A power law and a single, or a composition of, synchrotron component/s reproduce the cm radio wavelengths. We combined and extrapolated both fits to compare the extrapolation of both torus and jet contributors at sub-mm wavelengths with data at these wavelengths. Our observational results are consistent with our theoretical results. The most promising candidate to detect the torus is the QSO IZw1 (therefore, highly accreting sources in general), although it cannot be resolved due to the distance of this source. We suggest that to explore the detection of a torus at sub-mm wavelengths, it is necessary to perform an SED analysis including radio data, with particular attention to the angular resolution.