Hidden feedback from compact jets in LLAGN: a massive CO-dark outflow in ESO 420-G13
Juan Anton Fernández-Ontiveros (Centro de Estudios de Física del Cosmos de Aragón)
Tuesday 05/05/2026 @ 14:00, Sala Antonio Sollima (IV piano Battiferro)
Compact jets in low-luminosity AGN are increasingly recognised as potentially important sources of mechanical feedback in galaxies, but direct evidence that they can efficiently couple to the interstellar medium (ISM) of their hosts remains scarce. We present JWST/MIRI integral-field spectroscopy and ALMA CO(2-1) observations of ESO 420-G13, a post-starburst galaxy hosting an X-ray-faint LLAGN (L_2-10 keV ~ 10^40 erg/s), and show that a compact jet, nearly invisible in conventional diagnostics, is injecting substantial kinetic power into the surrounding interstellar medium. The MIRI data reveal a highly collimated coronal gas structure, traced by the [Ne V] and [Ne VI] emission lines and co-spatial with extended Chandra X-ray continuum emission reaching projected distances of about 870 pc from the nucleus. The interaction is strongest about 370 pc north of the nucleus, where a fast ionised gas stream (-1200 to -500 km/s) emerges perpendicular to the jet axis, coincident with a bend in the jet direction. An expanding warm H2 bubble surrounds this stream, with two distinct molecular outflows at its edges: a redshifted component detected in both cold CO(2-1) and warm H2, and a blueshifted outflow detected only in warm H2, that is, a CO-dark outflow. The lack of CO emission in the latter points to shock- and/or cosmic-ray-driven CO dissociation at the jet-ISM interaction front, rendering roughly half of the total outflowing molecular mass (4 x 10^6 Msun) invisible to conventional cold-gas tracers. Despite the radiatively faint nucleus, we estimate a total outflow kinetic power of ~1.5 x 10^41 erg/s, implying a jet-ISM coupling efficiency of ~3.8%. Roughly 5% of the central molecular reservoir has already been expelled, while the remaining gas is turbulent and warm, indicating an active phase of mechanically driven quenching in this post-starburst host. ESO 420-G13 demonstrates that compact, low-power jets can achieve substantial coupling efficiencies through a cascade