Speaker
Description
Understanding the structure and physical conditions of the active galactic nucleus (AGN) is essential for tracing how AGN interact with their host galaxies. High resolution multi-wavelength observations are required to probe the obscuring region directly, yet heavily dust-enshrouded systems often lack proper tracers. JWST overcomes many of these limitations, providing unprecedented sensitivity to the molecular gas that shapes torus obscuration and drives feedback. I will present JWST MIRI/MRS observations of the nearby ULIRG IRAS 07251 (~400 Mpc), selected for its exceptionally rich mid-IR molecular spectrum and extreme cosmic-ray ionization rate (ζH₂ ~10¹⁴ s⁻¹). The MIRI/MRS spectrum reveals numerous absorption features from ro-vibrational transitions of molecules (e.g., HCN v₂, HC₃N v₅, HCO⁺ v₂, N₂H⁺ v₂, HCNH⁺ v₄), arising from a compact shell located ~20–75 pc from the nucleus. These molecules exhibit column densities of ~10¹⁵–10¹⁸ cm⁻², rotational temperatures of 40–180 K, and outflow velocity of ~160 km/s corresponding to a mass outflow rate of 90–330 M⊙/yr. This warm molecular outflow is potentially tracing the base of the larger-scale cold molecular outflow previously detected in this galaxy. Comparing with predictions from chemical models, all detected species are consistent with originating in a cosmic-ray-dominated region. These results provide the first attempt to probe the physical and kinematic conditions of the material that is obscuring the AGN down to tens of parsecs, offering new insights into torus structure and feedback. I will also present spatially resolved maps of phase-specific obscuration levels in a sample of five nearby (U)LIRGs, demonstrating how JWST enables a new, multi-phase view of obscuration and of the molecular gas content of AGN.