Modeling the SED of the AGN inside NGC 4395

TL;DR

This study models the broad-band spectral energy distribution of the low-mass AGN in NGC 4395, highlighting the challenges of disentangling nuclear and galaxy emissions due to variability and model degeneracies.

Contribution

It applies combined optical to mid-infrared modeling with smooth and clumpy torus models to analyze a low-mass AGN, emphasizing the need for high-resolution data.

Findings

AGN dominates most wavelengths at arcsecond scales

Degeneracies remain in model fits despite full spectral coverage

High-resolution JWST observations are essential for clarity

Abstract

We study the broad-band spectral energy distribution (SED) of the prototypical low-mass active galactic nucleus (AGN) in NGC 4395. We jointly model the optical through mid-infrared SED with a combination of galaxy and AGN light, and find that on arcsecond scales, the AGN dominates at most wavelengths. However, there is still some ambiguity about emission from the galaxy, owing partially to the strong short-term variability of the black hole. We investigate the use of smooth and clumpy-torus models in order to disentangle the nuclear infrared emission, as well as exploring the use of poloidal wind emission to account for the blue spectral slope observed in the near-IR. Even when simultaneously fitting the full optical-IR spectral range, we find that degeneracies still remain in the best-fit models. We conclude that high spatial resolution and wider wavelength coverage with the James Webb Space Telescope is needed to understand the mid-infrared emission in this complex highly-variable object, which is the best nearby example to provide a blueprint to finding other low-mass AGN via their mid-infrared emission in the future.