I Zw 1 and H0557-385: The Dusty Tori of Two High Eddington AGNs Observed in the MATISSE LM-Bands

TL;DR

This study uses high-resolution interferometry to investigate the dust structures of two high Eddington ratio AGNs, revealing that their inner dust regions are disk-like and likely shaped by accretion rate-driven radiation pressure, affecting wind launching.

Contribution

It provides the first detailed interferometric analysis of high Eddington AGNs' dust structures, highlighting the influence of accretion rate on wind launching regions.

Findings

Dust sizes are wavelength-independent in H0557-385, indicating a direct view of the wind launching region.

Both AGNs show a disky, equatorial dust distribution consistent across multiple wavelengths.

Inner dust structures are shaped by the Eddington ratio, affecting wind direction and launching regions.

Abstract

The torus in Active Galactic Nuclei (AGN) is a complex dynamical structure of gas and dust. It is thought to be composed of an equatorial dusty disk and a polar dusty wind launched by radiation pressure. However, this picture is based on studies of moderately accreting AGN. Models suggest that the disk/wind structure will change with specific accretion rate. Here we examine the wind launching region in two high accretion rate objects, I Zw 1 (super-Eddington) and H0557-385 (high-Eddington), using high spatial resolution interferometric observations in the $K$-band from VLTI/GRAVITY and $LM$-bands VLTI/MATISSE. We recover wavelength-dependent sizes of the dust emission using a Gaussian and power law fit to the visibilities. Both objects are partially resolved and have radial sizes in the $KLM$-bands between 0.3 - 1.5 mas, with no signs of elongation. Combining our measurements with VLTI/MIDI $N$-band data gives a full multi-wavelength picture of the dust structure. We find that in H0557-385, the dust sizes between $3.5-8\:\mu\mathrm{m}$ are independent of the wavelength, roughly constant at $3-10$ sublimation radii. We argue that this indicates a direct view of the wind launching region and, together with an absence of polar elongation, this implies that any wind would be launched in a preferentially equatorial direction or blown out by strong radiation pressure. The size-wavelength relation for both objects shows a preferentially disky equatorial dust distribution. We conclude that there is strong evidence that the Eddington ratio shapes the inner dust structure, most notably the wind-launching region and wind direction.