GATOS. VIII. On the physical origin of the extended MIR emission in AGN

TL;DR

The study addresses the origin of extended polar MIR emission in AGN by leveraging JWST/MIRI imaging (10-21 μm) and JWST/MRS IFU data (7-25 μm) for six nearby AGN at ~75 pc resolution. It separates line-dominated from continuum-dominated emission and analyzes their spatial correlation relative to outflows, finding poor correlation between line- and continuum-only images and locating line emission along the jet axis while dust continuum emission lies perpendicular to it. The data yield a fairly uniform dust temperature around ~132 K and a dust mass of ~728 M⊙ in the extended continuum, with energy-balance analysis placing the sample in a gravitationally bound regime and showing no evidence for dusty winds. At 10 μm, extended line emission scales with outflow kinetic energy and mass outflow rates, but shows no clear dependence on intrinsic AGN properties, suggesting the radio jet may trigger gas outflows and line emission while the extended dust traces ambient molecular clouds or shocked regions, refining the understanding of the polar MIR component.

Abstract

The polar mid-infrared (MIR) emission detected within 10-100s pcs in some active galactic nuclei (AGN) has been associated with dusty winds driven away by radiation pressure. The physical characterization of this extended polar emission remains uncertain. Here we combine 10-21 $μ$m JWST/MIRI imaging observations with 7-25 $μ$m JWST/MRS integral field spectroscopic observations of 6 nearby, $\bar{D}=35.4\pm4.6$ Mpc, AGN from the GATOS Survey to quantify the nature of the extended MIR emission at ~75 pc resolution at 21 $μ$m. These AGN have similar bolometric luminosities, $\log_{10}(\bar{L}_{bol}\,[erg\,s^{-1}])=44.0\pm0.3$, span a wide range of optical outflow rates, $\dot{M}=0.003-0.21$ M$_{\odot}$ yr$^{-1}$, column densities, $\log_{10}(N_{H}^{X-ray}[cm^{-2}])=22.2-24.3$, and Eddington ratios, $λ_{Edd}=0.005-0.06$. We cross-correlate the line-only and continuum-only images and find a poor correlation, which indicates that the extended MIR continuum emission is spatially uncorrelated with the warm outflows associated with narrow emission lines within 10-15 $μ$m. Line emission is resolved along the jet axis, while dust emission is perpendicular to it. The 75-450 pc continuum emission has a fairly constant dust temperature, $T_{d}=132^{+7}_{-7}$ K, and mass, $M_{d}=728^{+29}_{-27}$ M$_{\odot}$. Using the conditions of energy balance between radiation-pressure and gravity ($λ_{Edd}$ vs. N$_{H}$), we find that our AGN sample is in the gravitationally bounded regime consistent with no detection of dusty winds. At 10 $μ$m, the level of extended line emission contribution is correlated with the outflow kinetic energy and mass outflow rates. We find no correlation with the AGN properties. These results indicate that the radio jet may be triggering the gas outflow and line emission, while the extended dust emission is distributed in molecular clouds and/or shocked regions.