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Arxiv: A biconical ionised gas outflow and evidence for positive feedback in NGC 7172 uncovered by MIRI/JWST Published: 7/22/2024 8:20:31 PM Updated: 7/22/2024 8:20:31 PM

Paper abstract: We present observations of the type-2 Seyfert NGC7172 obtained with themedium-resolution spectrometer (MRS) of the Mid-Infrared Instrument (MIRI) onboard of the JWST. This galaxy hosts one of the lowest ionised gas mass outflowrates (Mout~0.005 M/yr) in a sample of six AGN with similar bolometricluminosities (log Lbol~44erg/s) within the Galactic Activity, Torus and OutflowSurvey (GATOS). We aim to understand the properties of the ionised gas outflow,mainly using the emission lines from the neon transitions, that cover a broadrange of ionisation potentials (IP) from ~20 eV to ~130 eV. We appliedparametric and non-parametric methods to characterise the line emission andkinematics. The low excitation lines (IP<25eV, e.g.[NeII]) trace the rotatingdisc emission. The high excitation lines (IP>90eV, e.g.[NeV]), which are likelyphotoionised exclusively by the AGN, are expanding in the direction nearlyperpendicular to the disc of the galaxy, with maximum projected velocities of~350-500 km/s. In particular, [NeV] and [NeVI] lines reveal a biconical ionisedgas outflow emerging N-S from the nuclear region, extending at least ~2.5"N and3.8"S (projected distance of ~450 and 680 pc). Most of the emission arising inthe northern part of the cone was not previously detected due to obscuration.Given the almost face-on orientation of the outflow and the almost edge-onorientation of the galaxy, NGC7172 may be a case of weak coupling.Nevertheless, we found evidence for positive feedback in two distinctoutflowing clumps at projected distances of 3.1" and 4.3" (i.e. ~560 and 780pc) SW from the AGN. We estimated a star formation rate in these regions usingthe [NeII] and [NeIII] luminosities of 0.08 M/yr, that is ~10% of that found inthe circumnuclear ring. The star formation activity might have been triggeredby the interaction between the ionised gas outflow and the ISM of the galaxy.